ASTM G193-22

Standard Terminology and Acronyms Relating to Corrosion

SCOPE
1.1 This terminology and acronyms standard covers and defines commonly used terms and acronyms in the field of corrosion. Related terms may be found in Terminologies D16, D4538, G40, or other ASTM terminology standards.  
1.2 This terminology and acronyms standard is a result of an agreement between NACE International and ASTM International Committee G01 on Corrosion of Metals and may not reflect the opinions of other ASTM committees.  
1.3 In this terminology and acronyms standard, brackets are used for directives that follow a definition and are obviously not part of it, such as, “[see XXX]” and “[also known as XXX].” Brackets can also indicate the field of application or context of the definition or acronym.  
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-Jul-2022
• ICS: 01.040.77 - Metallurgy (Vocabularies)
• ICS: 77.060 - Corrosion of metals
• Technical Committee: J01 - Joint ASTM/NACE Committee on Corrosion
• Drafting Committee: J01.02 - Working Group on Terminology

Relations

• Refers: ASTM D16-24 - Standard Terminology for Paint, Related Coatings, Materials, and Applications
• Effective Date: 01-Jan-2024
• Refers: ASTM E18-18 - Standard Test Methods for Rockwell Hardness of Metallic Materials
• Effective Date: 01-Jul-2018
• Refers: ASTM E18-17 - Standard Test Methods for Rockwell Hardness of Metallic Materials
• Effective Date: 01-Jul-2017
• Refers: ASTM D16-16 - Standard Terminology for Paint, Related Coatings, Materials, and Applications
• Effective Date: 01-Jul-2016
• Refers: ASTM G40-15 - Standard Terminology Relating to Wear and Erosion
• Effective Date: 01-Nov-2015
• Refers: ASTM D16-14 - Standard Terminology for Paint, Related Coatings, Materials, and Applications
• Effective Date: 01-Dec-2014
• Refers: ASTM E10-14 - Standard Test Method for Brinell Hardness of Metallic Materials
• Effective Date: 01-May-2014
• Refers: ASTM D4538-13 - Standard Terminology Relating to Protective Coating and Lining Work for Power Generation Facilities
• Effective Date: 01-Nov-2013
• Refers: ASTM G40-13 - Standard Terminology Relating to Wear and Erosion
• Effective Date: 01-Jun-2013
• Refers: ASTM D2583-13 - Standard Test Method for Indentation Hardness of Rigid Plastics by Means of a Barcol Impressor
• Effective Date: 15-Mar-2013
• Refers: ASTM E18-12 - Standard Test Methods for Rockwell Hardness of Metallic Materials
• Effective Date: 01-Dec-2012
• Refers: ASTM D16-12 - Standard Terminology for Paint, Related Coatings, Materials, and Applications
• Effective Date: 01-Aug-2012
• Refers: ASTM G40-12 - Standard Terminology Relating to Wear and Erosion
• Effective Date: 01-May-2012
• Refers: ASTM E10-12 - Standard Test Method for Brinell Hardness of Metallic Materials
• Effective Date: 01-Jan-2012
• Refers: ASTM E18-11 - Standard Test Methods for Rockwell Hardness of Metallic Materials
• Effective Date: 01-Nov-2011

Overview

ASTM G193-22: Standard Terminology and Acronyms Relating to Corrosion is a comprehensive standard developed collaboratively by ASTM International and NACE International Committee G01. This standard defines and standardizes the most essential terms and acronyms commonly used in the field of corrosion, providing a vital reference for industry professionals, researchers, and regulatory bodies worldwide. By establishing clear, consistent language, ASTM G193-22 enhances communication, improves safety, and supports quality assurance across a range of industries affected by corrosion processes.

Key Topics

ASTM G193-22 covers a broad set of themes related to corrosion and its terminology:

• Core Terms and Acronyms: Explains standard definitions for corrosion mechanisms, testing methods, materials, and corrosion prevention techniques.
• Usage of Brackets: Outlines how brackets indicate explanatory notes, alternative names, or specific contexts within definitions.
• Collaborative Framework: Represents terminology harmonized by ASTM and NACE, reflecting consensus within the global corrosion engineering community.
• Reference to Related Documents: Identifies other ASTM terminology standards, such as ASTM D16, D4538, and G40, containing supplementary or related definitions.
• Compliance with International Principles: Developed according to World Trade Organization (WTO) Technical Barriers to Trade (TBT) guidelines for international standardization.

Applications

Adoption of ASTM G193-22 brings significant practical benefits in various sectors:

• Industrial Asset Management: Provides a reliable reference for asset integrity teams working on pipelines, storage tanks, bridges, and marine structures to specify, inspect, and maintain assets prone to corrosion.
• Design and Engineering Documentation: Ensures clear, accurate, and universally understood terminology in engineering drawings, technical reports, project specifications, and maintenance manuals.
• Standards Compliance and Safety: Supports legal and regulatory compliance regarding corrosion-resistant materials and technologies; essential for audits and certifications.
• Education and Training: Serves as a foundational text for educational programs, onboarding, and professional development in corrosion science and engineering.
• Research and Development: Enables researchers to accurately communicate findings and innovations related to corrosion phenomena, corrosion inhibitors, coating technologies, and testing protocols.
• Product Testing and Quality Control: Assists laboratories and manufacturers in precise reporting of test results and product certifications using standardized nomenclature.

Related Standards

The ASTM G193-22 terminology standard is aligned with and references several important related standards, including:

• ASTM D16: Terminology for Paint, Related Coatings, Materials, and Applications
• ASTM D4538: Terminology Relating to Protective Coating and Lining Work for Power Generation Facilities
• ASTM G40: Terminology Relating to Wear and Erosion
• ISO Standards: Including ISO 6506-1 (Brinell hardness test), ISO 6507-1 (Vickers hardness test), and ISO 6508-1 (Rockwell hardness test)
• NACE/AMPP Standards: For surface preparation and corrosion protection, such as NACE No. 1/SSPC-SP 5 and NACE No. 2/SSPC-SP 10
• SSPC Standards: For various cleaning and surface preparation processes (e.g., SSPC-SP 1, SP 2, SP 3, SP 8)

Conclusion

By offering consistent and universally recognized corrosion terminology, ASTM G193-22 facilitates better understanding, communication, and implementation of corrosion control strategies. Its broad applicability and thorough cross-referencing make it an indispensable tool for anyone involved in corrosion science, engineering, or management. For additional technical details, accompanying standards, and updates, refer directly to the official publications from ASTM International and NACE/AMPP.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: NACE/ASTM G193 − 22
Standard Terminology and Acronyms Relating to
Corrosion
This standard is issued under the fixed designation NACE/ASTM G193; the number immediately following the designation indicates
the year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last
reapproval. A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope E18 Test Methods for Rockwell Hardness of Metallic Ma-
terials
1.1 This terminology and acronyms standard covers and
E92 Test Methods for Vickers Hardness and Knoop Hard-
defines commonly used terms and acronyms in the field of
ness of Metallic Materials
corrosion. Related terms may be found in Terminologies D16,
G40 Terminology Relating to Wear and Erosion
D4538, G40, or other ASTM terminology standards.
2.2 NACE Standards:
1.2 Thisterminologyandacronymsstandardisaresultofan
NACE No. 1/SSPC-SP 5 White Metal Blast Cleaning
agreement between NACE International and ASTM Interna-
NACE No. 2/SSPC-SP10 Near-White Metal Blast Cleaning
tional Committee G01 on Corrosion of Metals and may not
NACE No. 3/SSPC-SP 6 Commercial Blast Cleaning
reflect the opinions of other ASTM committees.
NACE No. 4/SSPC-SP 7 Brush-Off Blast Cleaning
1.3 In this terminology and acronyms standard, brackets are
2.3 SSPC Surface Preparation Standards:
used for directives that follow a definition and are obviously
SSPC-SP 1 Solvent Cleaning
not part of it, such as, “[see XXX]” and “[also known as
SSPC-SP 2 Hand Tool Cleaning
XXX].” Brackets can also indicate the field of application or
SSPC-SP 3 Power Tool Cleaning
context of the definition or acronym.
SSPC-SP 8 Pickling
1.4 This international standard was developed in accor-
2.4 ISO Standards:
dance with internationally recognized principles on standard-
ISO 6506-1 Metallic materials -- Brinell hardness test -- Part
ization established in the Decision on Principles for the
1: Test method
Development of International Standards, Guides and Recom-
ISO 6507-1 Metallic materials -- Vickers hardness test --
mendations issued by the World Trade Organization Technical
Part 1: Test method
Barriers to Trade (TBT) Committee.
ISO 6508-1 Metallic materials -- Rockwell hardness test --
Part 1: Test method (scales A, B, C, D, E, F, G, H, K, N,
2. Referenced Documents
T)
2.1 ASTM Standards:
3. Terminology
D16 TerminologyforPaint,RelatedCoatings,Materials,and
Applications
3.1 Definitions:
D2583 Test Method for Indentation Hardness of Rigid Plas-
abrasion resistance—the ability of a material to resist being
tics by Means of a Barcol Impressor (Withdrawn 2022)
worn away and to maintain its original appearance and
D4538 Terminology Relating to Protective Coating and
structure when subjected to rubbing, scraping, or wear.
Lining Work for Power Generation Facilities
abrasive—a solid substance that, owing to its hardness,
E10 Test Method for Brinell Hardness of Metallic Materials
toughness, size, shape, consistency, or other properties, is
suitable for grinding, cutting, roughening, polishing, or
cleaning a surface by friction or high-velocity impact.
This terminology and acronyms standard is under the jurisdiction of NACE/
ASTM Committee J01, Joint Committee on Corrosion, and is the direct responsi-
abrasive blast cleaning—cleaning and roughening of a sur-
bility of Subcommittee J01.02, Working Group on Terminology.
Current edition approved Aug. 1, 2022. Published October 2022. Originally
faceproducedbythehigh-velocityimpactofanabrasivethat
approved in 2009. Last previous edition approved in 2021 as G193-21. DOI:
ispropelledbythedischargeofpressurizedfluidfromablast
10.1520/G0193-22.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on Available from The Association for Materials Protection and Performance
the ASTM website. For NACE standards, visit the The Association for Materials (AMPP), 800 Trumbull Drive, Pittsburgh, PA 15205, https://www.ampp.org/ampp-
Protection and Performance (AMPP) website, https://www.ampp.org/ampp-nace- sspc-store.
store. Available from International Organization for Standardization (ISO), ISO
The last approved version of this historical standard is referenced on Central Secretariat, BIBC II, Chemin de Blandonnet 8, CP 401, 1214 Vernier,
www.astm.org. Geneva, Switzerland, https://www.iso.org.
© NACE International/ASTM International 2022 – All rights reserved
NACE/ASTM G193 − 22
nozzle or by a mechanical device such as a centrifugal amphoteric metal—a metal that is susceptible to corrosion in
blasting wheel. [also referred to as abrasive blasting] both acidic and alkaline environments.
abrasive blasting—see abrasive blast cleaning.
anaerobic—absence of air or free (molecular) oxygen.
accelerator—a chemical substance that increases the rate at
anchor pattern—see surface profile.
which a chemical reaction (for example, curing) would
otherwise occur.
anion—a negatively charged ion.
AC impedance—see electrochemical impedance.
anneal—heat to and hold at a temperature appropriate for the
specific material and then cool at a suitable rate, for such
acrylic—type of resin polymerized from acrylic acid, meth-
purposes as reducing hardness, improving machinability, or
acrylic acid, esters of these acids, or acrylonitrile.
obtaining desired properties.
activator—a chemical substance that initiates a chemical
anode—the electrode of an electrochemical cell at which
reaction (for example, curing). Heat and radiation may also
serve as activators for some chemical reactions. oxidationoccurs.(Electronsflowawayfromtheanodeinthe
external circuit. It is usually the electrode where corrosion
active—(1) a state of a metal surface that is corroding without
occurs and metal ions enter solution.)
significant influence of reaction product. (2) the negative
direction of electrode potential.
anode cap—an electrical insulating material placed over the
end of the anode at the lead wire connection.
active-passive cell—an electrochemical cell in which the
anode is a metal in the active state and the cathode is the
anode corrosion efficiency—the ratio of the actual corrosion
same metal in the passive state.
(mass loss) of an anode to the theoretical corrosion (mass
loss) calculated from the quantity of electricity that has
adduct curing agent—amaterialthatisformedbyprereacting
passed between the anode and cathode using Faraday’s law.
the curing agent with a portion of the resin component of the
coating.
anodic inhibitor—a corrosion inhibitor whose primary action
adhesion—thestateinwhichtwosurfacesareheldtogetherby
is to reduce the rate of the anodic reaction, producing a
chemical interfacial forces, mechanical interlocking forces,
positive shift in corrosion potential.
or both.
anodic polarization—(1) the change of electrode potential
aeration cell—see differential aeration cell.
caused by an anodic current flowing across the electrode/
electrolyte interface. (2) a forced noble (positive) shift in
aging—(1) the process of exposing materials to an environ-
electrode potential. [See polarization.]
ment for an interval of time. (2) change in metallurgical
properties that generally occurs slowly at room temperature
anodic protection—atechniquetoreducethecorrosionrateof
(natural aging) and more rapidly at higher temperature
ametalsurfacebypolarizingthatsurfacetoamoreoxidizing
(artificial aging).
potential.
air drying—process by which an applied wet coat converts to
anodizing—an electrochemical oxidation process that con-
a dry coating film by evaporation of solvent or reaction with
verts the surface of a metal (such as aluminum or titanium)
oxygen as a result of simple exposure to air without
to an oxide coating.
intentional addition of heat or a curing agent.
anolyte—the electrolyte adjacent to the anode of an electro-
airless spraying—process of spraying coating liquids using
chemical cell.
hydraulic pressure, not air pressure, to atomize.
alkyd—type of resin formed by the reaction of polyhydric
antifouling—preventing fouling. [See fouling.]
alcohols and polybasic acids, part of which is derived from
atmospheric zone—the portion of a marine structure that
saturated or unsaturated oils or fats.
extends upward from the splash zone and is exposed to sun,
alligatoring—pronounced wide cracking over the surface of a
wind, water spray, and rain.
coating, which has the appearance of alligator hide.
attenuation—electrical losses in a conductor caused by cur-
alloy steel—an iron-based alloy containing carbon (usually
rent flow in the conductor.
less than 2.5 mass percent), manganese (usually greater than
0.25masspercent),andspecifiedminimumquantitiesofone
Auger electron spectroscopy—analytical technique in which
or more alloying elements other than manganese, silicon,
the sample surface is irradiated with low-energy electrons
andcopper,butdoesnotcontain10.5masspercentorgreater
and the energy spectrum of electrons emitted from the
chromium.
surface is measured.
alternate immersion—exposure to environmental cycles,
austenite—the face-centered cubic crystalline phase of iron or
each involving immersion in a fluid for a period of time
iron-based alloys.
followed by removal from that fluid for another period of
time. austenitic/ferritic stainless steel—see duplex stainless steel.
© NACE International/ASTM International 2022 – All rights reserved
NACE/ASTM G193 − 22
austenitizing—formingaustenitebyheatingironoriron-based bracelet anode—a galvanic anode with geometry suitable for
alloys to a temperature in the transformation range (partial direct attachment around the circumference of a pipeline.
austenitizing) or above the transformation range (complete This may be a half-shell bracelet consisting of two semicir-
austenitizing). cular sections or a segmented bracelet consisting of a large
number of individual sections.
auxiliary electrode—see counter electrode.
braze—(1) a bond produced as the result of heating an
backfill—material placed in a hole to fill the space around the
assembly to the brazing temperature greater than 450 °C
anodes, vent pipe, and buried components of a cathodic
[840 °F] and less than the solidus temperature of the base
protection system.
metal using a brazing filler metal distributed and retained
between the closely fitted faying surfaces of the joint by
Barcol hardness—ahardnessvalueobtainedbymeasuringthe
capillary action. (2) the act of creating a braze.
resistance of rubbers, plastics, or coatings to indentation by
a steel impressor under spring load in accordance with Test
breakdown potential—the least noble potential at which
Method D2583.
pitting or crevice corrosion, or both, will initiate and
propagate in a specific environment.
barrier coating—(1) a coating that has a high resistance to
permeation of liquids and/or gases. (2) a coating that is
Brinell hardness—hardness value, measured in accordance
applied over a previously coated surface to prevent damage with ISO 6506-1 or Test Method E10, using a 1 mm to
to the underlying coating during subsequent handling.
10 mm diameter tungsten carbide ball and a force of ap-
proximately 9.807 N to 29.420 N (1 kgf to 3000 kgf).
barrier pigment—apigmentthatimpedespermeationthrough
an organic coating solely by its physical presence [contrast brittle fracture—fracture that occurs with little or no plastic
deformation of the material. [contrast with ductile fracture]
with corrosion-inhibitive pigment and sacrificial pig-
ment].
brush-off blast cleaned surface—an abrasive blast cleaned
steel surface that is free of all visible contaminants and
beach marks—the characteristic markings on the fracture
foreign matter but may have some tightly adherent mill
surfacesproducedbyfatiguecrackpropagation.[alsoknown
scale, rust, or coating. [See NACE No. 4/SSPC-SP 7 for
as arrest marks, clamshell marks, and conchoidal marks]
detailed specification.]
beta curve—a plot of dynamic (fluctuating) interference
burnish—process of smoothing surfaces using frictional con-
current or related proportional voltage (ordinate) versus the
tact between the material and some other hard pieces of hard
corresponding structure-to-electrolyte potentials at a se-
material (for example, hardened steel balls).
lected location on the affected structure (abscissa).
calcareous coating—a layer consisting of calcium carbonate
binder—the nonvolatile portion of the vehicle of a formulated
and other salts deposited on the surface. When the surface is
coating material.
cathodically polarized as in cathodic protection, this layer is
bituminous coating—an asphalt or coal-tar compound used to the result of the increased pH adjacent to the protected
provide a protective coating for a surface. surface.
calcareous deposit—see calcareous coating.
blast angle—(1) the angle of the blast nozzle with reference to
the surface during abrasive blast cleaning. (2) the angle of
carbon steel—alloyofcarbonandironcontainingupto2mass
the abrasive particles propelled from a centrifugal blasting
percent carbon and up to 1.65 mass percent manganese and
wheel with reference to the surface being abrasive blast
residual quantities of other elements, except those intention-
cleaned.
ally added in specific quantities for deoxidation (usually
silicon and/or aluminum).
blister—a dome-shaped projection on the surface of a coating
resulting from the local loss of adhesion and lifting of the
carburizing—the absorption and diffusion of carbon in iron or
film from an underlying coat or from the base substrate.
an iron-based alloy in contact with a suitable carbonaceous
environment at elevated temperature.
blooming—see blushing.
case hardening—hardening a ferrous alloy so that the outer
blowdown—(1) the injection of air or water under high
portion, or case, is made substantially harder than the inner
pressure through a tube to the anode area for the purpose of
portion, or core. Typical processes are carburizing,
purging the annular space and possibly correcting high
cyaniding, carbonitriding, nitriding, induction hardening,
resistance caused by gas blockage. [cathodic protection use]
and flame hardening.
(2) the process of discharging a significant portion of the
aqueous solution in order to remove accumulated salts,
casein paint—water-thinned paint with vehicle derived from
deposits,andotherimpurities.[boilerorcoolingwatertower
milk.
use]
cast iron—a generic term for a large family of cast ferrous
blushing—whitening and loss of gloss of a coating, usually alloys in which the carbon content exceeds the solubility of
organic, caused by moisture. [also known as blooming] carbon in austenite at the eutectic temperature, or about 2
© NACE International/ASTM International 2022 – All rights reserved
NACE/ASTM G193 − 22
mass percent. Most cast irons also contain silicon, and may cementation—the introduction of one or more elements into
contain other alloying elements and impurities. the surface layer of a metal or alloy by diffusion at high
temperature. (Examples of cementation include carburizing
casting—(1) a component formed at or near its finished shape
[introduction of carbon], nitriding [introduction of nitrogen],
by the solidification of liquid material in a mold; (2) the
and chromizing [introduction of chromium].)
creation of such a component.
cementite—iron carbide (Fe C) when referred to as a micro-
catalyst—a chemical substance, usually present in small
structural constituent of steel.
amounts relative to the reactants, that increases the rate at
which a chemical reaction (for example, curing) would
chalking—the development of loose, removable powder (pig-
otherwise occur, but is not consumed in the reaction.
ment) at the surface of an organic coating, usually caused by
weathering.
cathode—the electrode of an electrochemical cell at which
reduction is the principal reaction. (Electrons flow toward
checking—the development of slight breaks in a coating that
the cathode in the external circuit.)
do not penetrate to the underlying surface.
cathodic corrosion—corrosionofametalwhenitisacathode,
chemical conversion coating—an adherent, reaction-product
usually caused by the reaction of an amphoteric metal with
layer on a metal surface formed in situ by reaction with a
the alkaline products of electrolysis.
suitable chemical, used for protective, decorative, or func-
tional purposes. (It is often used to provide greater corrosion
cathodic disbondment—the destruction of adhesion between
resistanceorpreparethesurfacepriortotheapplicationofan
a coating and the coated surface caused by products of a
organic coating.)
cathodic reaction.
chevron pattern—a V-shaped pattern on a fatigue or brittle-
cathodic inhibitor—a corrosion inhibitor whose primary ac-
fracture surface. The pattern can also be one of straight
tion is to reduce the rate of the cathodic reaction, producing
radial lines on cylindrical specimens.
a negative shift in corrosion potential.
chipping—(1) removing coating and surface contaminants
cathodic polarization—(1) the change of electrode potential
from a substrate in small pieces by cutting, striking, or
caused by a cathodic current flowing across the electrode/
applyingmechanicalforce; (2)afailuremechanisminwhich
electrolyte interface. (2) a forced active (negative) shift in
small pieces or fragments of a material or coating are
electrode potential. [See polarization.]
removed by mechanical damage, loss of adhesion, or both.
cathodic protection—a technique to reduce the corrosion rate
[contrast with peeling]
of a metal surface by making that surface the cathode of an
chloride stress corrosion cracking—cracking of a metal
electrochemical cell.
under the combined action of tensile stress and corrosion in
catholyte—the electrolyte adjacent to the cathode of an
thepresenceofanelectrolytecontainingdissolvedchlorides.
electrochemical cell.
cleavage fracture—fracture that occurs along planes deter-
cation—a positively charged ion.
mined by the crystal structure of the material. (It is typically
associated with a brittle fracture.)
caustic cracking—cracking of a metal or alloy under the
combined action of tensile stress and corrosion in the
coat—one layer of a coating system applied to a surface in a
presence of a strongly basic solution (for example, sodium
single continuous application to form a uniform film when
hydroxide, potassium hydroxide).
dry.
caustic embrittlement—an obsolete term referring to caustic
coating—(1) a liquid, liquefiable, or mastic composition that,
cracking.
after application to a surface, is converted into a solid
cavitation—the formation and rapid collapse of cavities or protective, decorative, or functional adherent film. (2) (in a
bubbles of vapor or gas within a liquid resulting from more general sense) a thin layer of solid material on a
mechanical or hydrodynamic forces. surface that provides improved protective, decorative, or
functional properties.
cavitation-corrosion—the conjoint action of cavitation and
corrosion.
coating system—the complete number and types of coats
applied to a substrate in a predetermined order. (When used
cavitation damage—the degradation of a solid body resulting
in a broader sense, surface preparation, pretreatments, dry
from its exposure to cavitation. (This may include loss of
film thickness, and manner of application are included.)
material, surface deformation, or changes in properties or
appearance.)
cold cracking—cracking of a weld during or after cooling to
ambient temperature, sometimes after a considerable time
cavitation-erosion—the conjoint action of cavitation and ero-
delay. (It usually occurs at temperatures less than 205 °C
sion.
[400 °F] for metals, and less than the glass transition
cell—see electrochemical cell. temperature for plastics.)
© NACE International/ASTM International 2022 – All rights reserved
NACE/ASTM G193 − 22
cold lap—alineardiscontinuitywithroundededgesatexposed swabbed onto the surface of certain metals to determine the
surfaces that is caused by solidification of the meniscus of a presence of metals more active (anodic) than copper. (2) a
partially cast metal or alloy (for example, an anode used for spot test method in whicha5to10 percent solution of
cathodic protection) as a result of interrupted flow of the copper sulfate in water is swabbed onto a steel surface to
casting stream or the joining of two casting streams at too determine whether mill scale is present. (The appearance of
low a temperature. copper indicates that mill scale is not present.)
cold shut—horizontal surface discontinuity caused by solidi-
corrosion—the deterioration of a material, usually a metal,
fication of a portion of a meniscus during the progressive
that results from a chemical or electrochemical reaction with
filling of a mold, which is later covered with more solidify-
its environment.
ing metal as the molten metal level rises. Cold shuts
corrosion-inhibitive pigment—a pigment that has the prop-
generally occur at corners remote from the point of pour.
erty of minimizing corrosion of the metal substrate to which
cold working—deforming metal plastically under conditions
the coating is applied by directly reducing the anodic or
of temperature and strain rate that induce strain hardening,
cathodic reactions, or both [contrast with sacrificial pig-
usually, but not necessarily, performed at room temperature
ment and barrier pigment].
[contrast with hot working]
corrosion fatigue—the process wherein a metal fractures
commercial blast cleaned surface—an abrasive blast cleaned
prematurely under conditions of simultaneous corrosion and
steel surface that is free of all visible contaminants and
repeated cyclic loading at lower stress levels or fewer cycles
foreign matter but may have some random staining on no
than would be required to cause fatigue of that metal in the
more than 33 percent of the surface area. [See NACE No.
absence of the corrosive environment.
3/SSPC-SP 6 for detailed specification.]
corrosion fatigue strength—the maximum repeated stress
compressive strength—the maximum compressive stress a
that can be endured by a metal without fracture under
material is capable of withstanding without sustaining per-
definite conditions of corrosion and cyclic loading for a
manent deformation.
specific number of stress cycles and a specified period of
time.
concentration cell—anelectrochemicalcell,theelectromotive
force of which is caused by a difference in concentration of
corrosion inhibitor—a chemical substance or combination of
some component in the electrolyte. (This difference leads to
substances that, when present in the proper concentration
the formation of discrete cathodic and anodic regions.)
and forms in the environment, reduces the corrosion rate.
concentration polarization—thatportionofpolarizationofan
corrosion potential—(represented by the symbol E ) the
corr
electrochemical cell produced by concentration changes
potential of a corroding surface in an electrolyte measured
resulting from current flowing through the electrolyte.
under open-circuit conditions relative to a reference elec-
conductive coating—(1) a coating that conducts electricity.
trode. [also known as electrochemical corrosion potential,
(2) an electrically conductive, mastic-like material used as
free corrosion potential, open-circuit potential ]
an impressed current anode on reinforced concrete surfaces.
corrosion rate—the time rate of change of corrosion. (It is
conductive concrete—a highly conductive cement-based mix-
typically expressed as mass loss per unit area per unit time,
ture containing coarse and fine coke and other material used
penetration per unit time, etc.)
as an impressed current anode on reinforced concrete sur-
faces. corrosion resistance—ability of a material, usually a metal, to
withstand corrosion in a given environment.
conductivity—(1) a measure of the ability of a material to
conduct an electric charge. (2) the current transferred across corrosion under insulation—deterioration that occurs on an
a material (for example, coating) per unit area per unit
insulated component such as a pipe, vessel, or structural
potential gradient. (Conductivity is the reciprocal of resis- member as a result of water or other corrodents being
tivity.)
trapped against the component by the insulating material.
DISCUSSION—Insulating materials may include, but are not limited to,
contact corrosion—see galvanic corrosion.
thermal insulation, electrical insulation, acoustic insulation, and fire-
proofing.
continuity bond—a connection, usually metallic, that pro-
vides electrical continuity between structures that can con-
corrosiveness—the tendency of an environment to cause
duct electricity.
corrosion.
continuous anode—a single anode with no electrical discon-
counter electrode—the electrode in an electrochemical cell
tinuities.
that is used to transfer current to or from a working
electrode.
conversion coating—see chemical conversion coating.
copper sulfate test—(1) a test method in which a solution of counterpoise—a conductor or system of conductors arranged
copper sulfate, and possibly other ingredients, in water is beneath a power line, located on, above, or most frequently,
© NACE International/ASTM International 2022 – All rights reserved
NACE/ASTM G193 − 22
below the surface of the earth and connected to the footings charges. (In a metallic conductor, this is the opposite
of the towers or poles supporting the power line. direction of the electron flow.)
couple—see galvanic couple.
current density—the electric current flowing to or from a unit
area of an electrode surface.
coupon—a portion of a material or sample, usually flat, but
occasionally curved or cylindrical, from which one or more
current efficiency—the ratio of the electrochemical equivalent
specimens can be taken for testing.
current density for a specific reaction to the total applied
current density.
crack—(1) a partial split or break. (2) a split or break in a
coating that penetrates to the substrate.
DC decoupling device—a device used in electrical circuits
that allows the flow of alternating current in both directions
cracking—fracture of a material along a path that produces a
and stops or substantially reduces the flow of direct current.
linear discontinuity (without complete separation).
deactivation—the process of prior removal of the active
crater—(1) a metal surface anomaly consisting of a bowl-
corrosive constituents, usually oxygen, from a corrosive
shaped cavity with the minimum dimension at the opening
liquid by controlled corrosion of expendable metal or by
greater than the depth. [contrast with pit] (2) a small,
other chemical means, thereby making the liquid less corro-
rounded dish or bowl-like depression in a wet-applied
sive.
coating. [contrast with fish eye]
dealloying—acorrosionprocesswherebyoneconstituentofan
crazing—a network of checks or cracks appearing on the
alloy is preferentially removed, leaving an altered residual
surface of a coating.
structure. [also known as parting, selective dissolution,or
selective leaching]
creep—time-dependent strain occurring under stress.
creep strength—that stress which, when applied to a material decomposition potential—the potential of an electrode sur-
at a specific temperature, will cause a specified amount of face at which the electrolyte, or a component thereof,
elongation in a specified time. decomposes by electrolysis.
crevice corrosion—localized corrosion of a metal or alloy decomposition voltage—see decomposition potential.
surface at, or immediately adjacent to, an area that is
deep groundbed—one or more anodes installed vertically at a
shielded from full exposure to the environment because of
nominal depth of 15 m (50 ft) or more below the earth’s
closeproximityofthemetaloralloytothesurfaceofanother
surface in a drilled hole for the purpose of supplying
material or an adjacent surface of the same metal or alloy.
cathodic protection current.
critical anodic current density—themaximumanodiccurrent
delamination—(1) separation of layers in a material. (2) a
density observed in the active region for a metal or alloy
separation between one or more coats from another coat
electrode that exhibits active-passive behavior in an envi-
within a coating system. [contrast with disbondment] (3) a
ronment.
separation of the concrete (usually in layers) from the
critical humidity—the relative humidity above which the
reinforcing steel at their interface, usually as a result of
atmospheric corrosion rate of a specific metal or alloy
corrosion.
increases sharply.
delayed cracking—(1) cracking in a metal occurring after
critical pitting potential—(represented by the symbol E or
p plating or pickling, sometimes after a considerable time
E ) the least noble potential at which pitting corrosion will
pp delay. (2) not a preferred term for cold cracking.
initiateandpropagateinaspecificenvironment.[See break-
depolarization—(not a preferred term) the removal of factors
down potential.]
resisting the current flow in an electrochemical cell. [See
curing—process of developing the intended properties of a
polarization.]
coating or other material (for example, resin) over a period
deposit corrosion—localized corrosion under or around a
of time.
deposit or collection of material on a metal surface. [also
curing agent—a chemical substance used for curing a coating
called poultice corrosion] [See also crevice corrosion.]
or other material (for example, resin). [also referred to as
dezincification—dealloying that results in the selective re-
hardener]
moval of zinc from copper-zinc alloys.
curing time—the minimum period between application and
the time at which the applied material attains its intended dielectric coating—a coating that does not conduct electricity.
physical properties.
dielectric shield—anelectricallynonconductivematerial,such
current—(1) a flow of electric charge. (2) the amount of as a coating, sheet or pipe, that is placed between an anode
electric charge flowing past a specified circuit point per unit and an adjacent cathode, usually on the cathode, to improve
time, measured in the direction of net transport of positive current distribution in a cathodic protection system.
© NACE International/ASTM International 2022 – All rights reserved
NACE/ASTM G193 − 22
differential aeration cell—a concentration cell caused by drying time—minimum time required for an applied coating
differences in oxygen concentration along the surface of a to reach the desired stage of drying or curing.
metal in an electrolyte. [See concentration cell.]
ductile cast iron—cast iron that has been treated while molten
diffusion-limited current density—the current density that
with an element (usually magnesium or cerium) that
corresponds to the maximum transfer rate that a particular
spheroidizes the graphite. [also called nodular cast iron].
species can sustain because of the limitation of diffusion
ductile fracture—fracture that occurs with appreciable plastic
[often referred to as limiting current density]
deformation of the material. [contrast with brittle fracture]
disbondment—the loss of adhesion between a coating and the
ductility—the ability of a material to withstand plastic defor-
substrate.
mation prior to fracture. (It is usually measured by the
discontinuity—(1) an interruption in the normal physical
permanentelongationorreductioninthecross-sectionalarea
structure or configuration of a coating such as cracks, laps,
of a fractured tensile test specimen.)
seams, inclusions, porosity, or holidays. (A discontinuity
does not necessarily affect the usefulness of the coating.) (2) duplex stainless steel—stainless steel whose microstructure at
a condition in which the electrical path through a structure is
room temperature consists primarily of a mixture of austen-
interrupted by a device that acts as a dielectric or insulating ite and ferrite. [also called austenitic/ferritic stainless
fitting.
steel].
dissimilar metals—different metals that could form an anode-
elastic deformation—changes of dimensions of a material
cathode relationship in an electrolyte when connected by an
upon the application of a stress within the elastic range.
electron-conducting (usually metallic) path.
Followingthereleaseofanelasticstress,thematerialreturns
to its original dimensions without any permanent deforma-
double layer—the interface between an electrode or a sus-
tion.
pended particle and an electrolyte created by charge-charge
interaction leading to an alignment of oppositely charged
elasticity—the property of a material that allows it to recover
ions at the surface of the electrode or particle. The simplest
its original dimensions following deformation by a stress
model is represented by a parallel plate condenser.
below its elastic limit.
doubler plate—an additional plate or thickness of metal used
elastic limit—the maximum stress to which a material may be
to provide extra strength or thickness to a structure locally
subjected without retention of any permanent deformation
(for example, at the point of anode attachment to an offshore
after the stress is removed.
structure).
electrical interference—any electrical disturbance on a me-
drainage—conductionofelectriccurrentfromanunderground
tallic structure in contact with an electrolyte caused by stray
or submerged metallic structure by means of a metallic
current(s).
conductor.
electrical isolation—the condition of being electrically sepa-
driving potential—difference in potential between the anode
rated from other metallic structures or the environment.
and the steel structure.
electrochemical admittance—the reciprocal of the electro-
dry film thickness—the thickness of a dried film, coating, or
chemical impedance, ∆I/∆E.
membrane.
electrochemical cell—(1) an electrochemical reaction involv-
dry spray—a rough, powdery noncoherent film produced
when atomized coating particles partially dry before reach- ing two half reactions, one of which involves oxidation of
the reactant (product) and the other of which involves
ing the surface.
reduction of the product (reactant). (The equilibrium poten-
dry to handle—stage of drying or curing of an applied coating
tial of the electrochemical cell can be calculated from the
at which time the coated object can be carefully handled
change in free energy for the overall electrochemical reac-
without damage.
tion. The equilibrium potential of the electrochemical cell
can be measured by separating the oxidation and reduction
dry to recoat—stage of drying or curing of an applied coating
half reactions into individual compartments and measuring
atwhichtimeasubsequentcoatcanbeappliedsatisfactorily.
the voltage that develops between them under conditions
dry to touch—stage of drying or curing of an applied coating
that virtually no charge passes between them.) [thermody-
at which time it no longer adheres to a finger that is lightly
namic use] (2) an electrochemical system consisting of an
touched or rubbed across the surface and does not show a
anode and a cathode in metallic contact and immersed in an
fingerprint at the point of contact.
electrolyte. (The anode and cathode may be different metals
or dissimilar areas on the same metal surface.) [common
drying—the process in which a liquid film is converted to a
use]
solid film by evaporation of volatile components.
drying oil—an oil capable of conversion from a liquid to a electrochemical corrosion potential—see corrosion poten-
solid by slow reaction with oxygen in the air. tial.
© NACE International/ASTM International 2022 – All rights reserved
NACE/ASTM G193 − 22
electrochemical equivalent—the mass of an element or group hydrogen such as gold and negative for those more active
of elements oxidized or reduced at 100 percent efficiency by than hydrogen such as zinc. [not to be confused with
the passage of a unit quantity of charge such as a Faraday galvanic series]
(96,485 coulombs), ampere-hour, or coulomb.
electro-osmosis—the migration of water through a semiper-
electrochemical impedance—the frequency dependent, com-
meablemembraneasaresultofapotentialdifferencecaused
plex valued proportionality factor, ∆I/∆E, between the ap-
by the flow of electric charge through the membrane.
plied potential (or current) and the response current (or
ellipsometry—an optical technique wherein plane-polarized
potential)inanelectrochemicalcell.Thisfactorbecomesthe
light is focused on a surface and the reflected beam is
impedance when the perturbation and response are related
analyzed to determine the phase shift of the components of
linearly (the factor value is independent of the perturbation
the light to provide information on the properties of films
magnitude) and the response is caused only by the pertur-
that may be present on the surface.
bation. The value may be related to the corrosion rate when
the measurement is made at the corrosion potential.
embrittlement—reduction of ductility, or toughness, or both,
of a material (usually a metal or alloy).
electrochemical noise—fluctuations of potential or current, or
both, originating from uncontrolled variations in a corrosion
EMF series—see electromotive force series.
process.
enamel—(1) a paint that dries to a hard, glossy surface. (2) a
electrochemical potential—the partial derivative of the total
coating that is characterized by an ability to form a smooth,
electrochemical free energy of the system with respect to the
durable film.
number of moles of the constituent in a solution when all
other factors are constant. (Analogous to the chemical
end effect—the more rapid loss of anode material at the end of
potential of the constituent except that it includes the
an anode, compared with other surfaces of the anode,
electrical as well as the chemical contributions to the free
resulting from higher current density.
energy.)
endurance limit—the maximum stress that a material can
electrode—a material that conducts electrons, is used to
withstand for an infinitely large number of fatigue cycles.
establish contact with an electrolyte, and through which
current is transferred to or from an electrolyte.
environment—the surroundings or conditions (physical,
chemical, mechanical) in which a material exists.
electrode potential—the potential of an electrode in an elec-
trolyte as measured against a reference electrode.
environmental cracking—see environmentally assisted
cracking.
electrokinetic potential—a potential difference in a solution
DISCUSSION—Environmental cracking is a general term that includes
caused by residual, unbalanced charge distribution in the
the terms listed below. The definitions of these terms are listed
adjoining solution, producing a double layer. (The electro-
elsewhere in this document: caustic cracking, chloride stress corro-
kinetic potential is different from the electrode potential in
sion cracking, corrosion fatigue, hydrogen embrittlement,
thatitoccursexclusivelyinthesolutionphase.Thispotential
hydrogen-induced cracking (stepwise cracking), hydrogen stress
represents the reversible work necessary to bring a unit
cracking, liquid metal cracking, stress corrosion cracking, sulfide
charge from infinity in the solution up to the interface in
stress cracking.
question but not through the interface.) [also known as zeta
DISCUSSION—The following terms have been used in the past in
potential]
connection with environmental cracking but are now obsolete and
should not be used: caustic embrittlement, delayed cracking, liquid
electrolysis—production of chemical changes of the electro-
metal embrittlement, season cracking, static fatigue, sulfide corrosion
lyte by the current flowing through an electrochemical cell.
cracking, sulfide stress corrosion cracking.
electrolyte—achemicalsubstancecontainingionsthatmigrate
environmentally assisted cracking—cracking of a material
in an electric field.
wherein an interaction with its environment is a causative
factor in conjunction with tensile stress, often resulting in
electrolytic corrosion—not a proper term, but sometimes
brittle fracture of an otherwise ductile material.
incorrectly used to refer to galvanic corrosion, stray-
current corrosion, or any form of electrochemical corro-
epoxy—type of resin formed by the reaction of aliphatic or
sion.
aromatic polyols (such as bisphenol) with epichlorohydrin
and characterized by the presence of reactive oxirane end
electrolytic cleaning—a process for removing soil, scale, or
groups.
corrosion products from a metal surface by subjecting the
metal as an electrode to an electric current in an electrolytic
equilibrium potential—the potential of an electrode in an
bath.
electrolyte at which the forward rate of a given reaction is
electromotive force series—a list of elements arranged ac- exactly equal to the reverse rate. (The equilibrium potential
cording to their standard electrode potentials, the sign being canonlybedefinedwithrespecttoaspecificelectrochemical
positive for elements whose potentials are more noble than reaction.) [also known as reversible potential]
© NACE International/ASTM International 2022 – All rights reserved
NACE/ASTM G193 − 22
erosion—the progressive loss of material from a solid surface filiform corrosion—corrosionthatoccursundersomecoatings
resulting from mechanical interaction between that surface in the form of randomly distributed threadlike filaments.
and a fluid, a multicomponent fluid, or solid particles carried
film—a thin, not necessarily visible layer of material.
with the fluid.
finish coat—see topcoat.
erosion-corrosion—a conjoint action involving erosion and
corrosion in the presence of a moving corrosive fluid or a
fish eye—a small dimple or crater with a visible defect or
material moving through the fluid, leading to accelerated
contaminant in the central area resembling a fish eye that
loss of material.
forms in a wet-applied coating. [see crater]
exchange current density—therateofchargetransferperunit flash rust—an iron oxidation product that forms rapidly on a
area when an electrode reaches dynamic equilibrium (at its
newly prepared ferrous metal surface exposed to moisture.
reversible potential) in a solution; that is, the rate of anodic
forced drainage—drainage applied to underground or sub-
charge transfer (oxidation) is exactly equal to the rate of
merged metallic structures by means of an applied electro-
cathodic charge transfer (reduction).
motive force or sacrificial anode.
exfoliation corrosion—subsurface corrosion that proceeds
foreign structure—any metallic structure that is not intended
laterally from the sites of initiation along planes parallel to
as a part of a system under cathodic protection.
thesurfaceformingcorrosionproductsthatforcemetalaway
from the body of the material, giving rise to a layered
fouling—an accumulation of deposits. (This includes accumu-
appearance resembling the pages of a book.
lation and growth of marine organisms on a submerged
surface and the accumulation of deposits on heat exchanger
external circuit—the wires, connectors, measuring devices,
tubing.)
current sources, etc., that are used to bring about or measure
the desired electrical conditions within an electrochemical
fractography—descriptive treatment of fracture, especially in
cell. It is this portion of the cell through which electrons
metals, with specific reference to photographs of the fracture
travel.
surface.
fatigue—the process of progressive localized permanent struc- fracture mechanics—a quantitative analysis for evaluating
tural change occurring in a material subjected to fluctuating structural reliability in terms of applied stress, crack length,
stresses less than the ultimate tensile strength of the material and specimen geometry.
that may culminate in cracks or complete fracture after a
free corrosion potential—see corrosion potential.
sufficient number of fluctuations.
free machining—the machining characteristics of an alloy to
fatigue strength—the maximum stress that can be sustained
which an ingredient has been introduced to give small
for a specified number of cycles without fracture.
broken chips, lower power consumption, better surface
finish, and longer tool life.
fault curre
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: NACE/ASTM G193 − 21
NACE/ASTM G193 − 22
Standard Terminology and Acronyms Relating to
Corrosion
This standard is issued under the fixed designation NACE/ASTM G193; the number immediately following the designation indicates
the year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last
reapproval. A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This terminology and acronyms standard covers and defines commonly used terms and acronyms in the field of corrosion.
Related terms may be found in Terminologies D16, D4538, G40, or other ASTM terminology standards.
1.2 This terminology and acronyms standard is a result of an agreement between NACE International and ASTM International
Committee G01 on Corrosion of Metals and may not reflect the opinions of other ASTM committees.
1.3 In this terminology and acronyms standard, brackets are used for directives that follow a definition and are obviously not part
of it, such as, “[see XXX]” and “[also known as XXX].” Brackets can also indicate the field of application or context of the
definition or acronym.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D16 Terminology for Paint, Related Coatings, Materials, and Applications
D2583 Test Method for Indentation Hardness of Rigid Plastics by Means of a Barcol Impressor (Withdrawn 2022)
D4538 Terminology Relating to Protective Coating and Lining Work for Power Generation Facilities
E10 Test Method for Brinell Hardness of Metallic Materials
E18 Test Methods for Rockwell Hardness of Metallic Materials
E92 Test Methods for Vickers Hardness and Knoop Hardness of Metallic Materials
G40 Terminology Relating to Wear and Erosion
2.2 NACE Standards:
NACE No. 1/SSPC-SP 5 White Metal Blast Cleaning
NACE No. 2/SSPC-SP 10 Near-White Metal Blast Cleaning
NACE No. 3/SSPC-SP 6 Commercial Blast Cleaning
NACE No. 4/SSPC-SP 7 Brush-Off Blast Cleaning
This terminology and acronyms standard is under the jurisdiction of NACE/ASTM Committee J01, Joint Committee on Corrosion, and is the direct responsibility of
Subcommittee J01.02, Working Group on Terminology.
Current edition approved Dec. 15, 2021Aug. 1, 2022. Published May 2022October 2022. Originally approved in 2009. Last previous edition approved in 20202021 as
G193-20a.-21. DOI: 10.1520/G0193-21.10.1520/G0193-22.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website. For NACE standards, visit the The Association for Materials Protection and
Performance (AMPP) website, https://www.ampp.org/ampp-nace-store.
The last approved version of this historical standard is referenced on www.astm.org.
© NACE International/ASTM International 2022 – All rights reserved
NACE/ASTM G193 − 22
2.3 SSPC Surface Preparation Standards:
SSPC-SP 1 Solvent Cleaning
SSPC-SP 2 Hand Tool Cleaning
SSPC-SP 3 Power Tool Cleaning
SSPC-SP 8 Pickling
2.4 ISO Standards:
ISO 6506-1 Metallic materials -- Brinell hardness test -- Part 1: Test method
ISO 6507-1 Metallic materials -- Vickers hardness test -- Part 1: Test method
ISO 6508-1 Metallic materials -- Rockwell hardness test -- Part 1: Test method (scales A, B, C, D, E, F, G, H, K, N, T)
3. Terminology
3.1 Definitions:
abrasion resistance—the ability of a material to resist being worn away and to maintain its original appearance and structure
when subjected to rubbing, scraping, or wear.
abrasive—a solid substance that, owing to its hardness, toughness, size, shape, consistency, or other properties, is suitable for
grinding, cutting, roughening, polishing, or cleaning a surface by friction or high-velocity impact.
abrasive blast cleaning—cleaning and roughening of a surface produced by the high-velocity impact of an abrasive that is
propelled by the discharge of pressurized fluid from a blast nozzle or by a mechanical device such as a centrifugal blasting wheel.
[also referred to as abrasive blasting]
abrasive blasting—see abrasive blast cleaning.
accelerator—a chemical substance that increases the rate at which a chemical reaction (for example, curing) would otherwise
occur.
AC impedance—see electrochemical impedance.
acrylic—type of resin polymerized from acrylic acid, methacrylic acid, esters of these acids, or acrylonitrile.
activator—a chemical substance that initiates a chemical reaction (for example, curing). Heat and radiation may also serve as
activators for some chemical reactions.
active—(1) a state of a metal surface that is corroding without significant influence of reaction product. (2) the negative direction
of electrode potential.
active-passive cell—an electrochemical cell in which the anode is a metal in the active state and the cathode is the same metal
in the passive state.
adduct curing agent—a material that is formed by prereacting the curing agent with a portion of the resin component of the
coating.
adhesion—the state in which two surfaces are held together by chemical interfacial forces, mechanical interlocking forces, or
both.
aeration cell—see differential aeration cell.
Available from The Association for Materials Protection and Performance (AMPP), 800 Trumbull Drive, Pittsburgh, PA 15205, https://www.ampp.org/ampp-sspc-store.
Available from International Organization for Standardization (ISO), ISO Central Secretariat, BIBC II, Chemin de Blandonnet 8, CP 401, 1214 Vernier, Geneva,
Switzerland, https://www.iso.org.
© NACE International/ASTM International 2022 – All rights reserved
NACE/ASTM G193 − 22
aging—(1) the process of exposing materials to an environment for an interval of time. (2) change in metallurgical properties
that generally occurs slowly at room temperature (natural aging) and more rapidly at higher temperature (artificial aging).
air drying—process by which an applied wet coat converts to a dry coating film by evaporation of solvent or reaction with
oxygen as a result of simple exposure to air without intentional addition of heat or a curing agent.
airless spraying—process of spraying coating liquids using hydraulic pressure, not air pressure, to atomize.
alkyd—type of resin formed by the reaction of polyhydric alcohols and polybasic acids, part of which is derived from saturated
or unsaturated oils or fats.
alligatoring—pronounced wide cracking over the surface of a coating, which has the appearance of alligator hide.
alloy steel—an iron-based alloy containing carbon (usually less than 2.5 mass percent), manganese (usually greater than 0.25
mass percent), and specified minimum quantities of one or more alloying elements other than manganese, silicon, and copper,
but does not contain 10.5 mass percent or greater chromium.
alternate immersion—exposure to environmental cycles, each involving immersion in a fluid for a period of time followed by
removal from that fluid for another period of time.
amphoteric metal—a metal that is susceptible to corrosion in both acidic and alkaline environments.
anaerobic—absence of air or free (molecular) oxygen.
anchor pattern—see surface profile.
anion—a negatively charged ion.
anneal—heat to and hold at a temperature appropriate for the specific material and then cool at a suitable rate, for such purposes
as reducing hardness, improving machinability, or obtaining desired properties.
anode—the electrode of an electrochemical cell at which oxidation occurs. (Electrons flow away from the anode in the external
circuit. It is usually the electrode where corrosion occurs and metal ions enter solution.)
anode cap—an electrical insulating material placed over the end of the anode at the lead wire connection.
anode corrosion efficiency—the ratio of the actual corrosion (mass loss) of an anode to the theoretical corrosion (mass loss)
calculated from the quantity of electricity that has passed between the anode and cathode using Faraday’s law.
anodic inhibitor—a corrosion inhibitor whose primary action is to reduce the rate of the anodic reaction, producing a positive
shift in corrosion potential.
anodic polarization—(1) the change of electrode potential caused by an anodic current flowing across the electrode/electrolyte
interface. (2) a forced noble (positive) shift in electrode potential. [See polarization.]
anodic protection—a technique to reduce the corrosion rate of a metal surface by polarizing that surface to a more oxidizing
potential.
© NACE International/ASTM International 2022 – All rights reserved
NACE/ASTM G193 − 22
anodizing—an electrochemical oxidation process that converts the surface of a metal (such as aluminum or titanium) to an oxide
coating.
anolyte—the electrolyte adjacent to the anode of an electrochemical cell.
antifouling—preventing fouling. [See fouling.]
atmospheric zone—the portion of a marine structure that extends upward from the splash zone and is exposed to sun, wind,
water spray, and rain.
attenuation—electrical losses in a conductor caused by current flow in the conductor.
Auger electron spectroscopy—analytical technique in which the sample surface is irradiated with low-energy electrons and the
energy spectrum of electrons emitted from the surface is measured.
austenite—the face-centered cubic crystalline phase of iron or iron-based alloys.
austenitic/ferritic stainless steel—see duplex stainless steel.
austenitizing—forming austenite by heating iron or iron-based alloys to a temperature in the transformation range (partial
austenitizing) or above the transformation range (complete austenitizing).
auxiliary electrode—see counter electrode.
backfill—material placed in a hole to fill the space around the anodes, vent pipe, and buried components of a cathodic protection
system.
Barcol hardness—a hardness value obtained by measuring the resistance of rubbers, plastics, or coatings to indentation by a
steel impressor under spring load in accordance with Test Method D2583.
barrier coating—(1) a coating that has a high resistance to permeation of liquids and/or gases. (2) a coating that is applied over
a previously coated surface to prevent damage to the underlying coating during subsequent handling.
barrier pigment—a pigment that impedes permeation through an organic coating solely by its physical presence [contrast with
corrosion-inhibitive pigment and sacrificial pigment].
beach marks—the characteristic markings on the fracture surfaces produced by fatigue crack propagation. [also known as arrest
marks,clamshell marks, and conchoidal marks]
beta curve—a plot of dynamic (fluctuating) interference current or related proportional voltage (ordinate) versus the
corresponding structure-to-electrolyte potentials at a selected location on the affected structure (abscissa).
binder—the nonvolatile portion of the vehicle of a formulated coating material.
bituminous coating—an asphalt or coal-tar compound used to provide a protective coating for a surface.
© NACE International/ASTM International 2022 – All rights reserved
NACE/ASTM G193 − 22
blast angle—(1) the angle of the blast nozzle with reference to the surface during abrasive blast cleaning. (2) the angle of the
abrasive particles propelled from a centrifugal blasting wheel with reference to the surface being abrasive blast cleaned.
blister—a dome-shaped projection on the surface of a coating resulting from the local loss of adhesion and lifting of the film
from an underlying coat or from the base substrate.
blooming—see blushing.
blowdown—(1) the injection of air or water under high pressure through a tube to the anode area for the purpose of purging
the annular space and possibly correcting high resistance caused by gas blockage. [cathodic protection use] (2) the process of
discharging a significant portion of the aqueous solution in order to remove accumulated salts, deposits, and other impurities.
[boiler or cooling water tower use]
blushing—whitening and loss of gloss of a coating, usually organic, caused by moisture. [also known as blooming]
bracelet anode—a galvanic anode with geometry suitable for direct attachment around the circumference of a pipeline. This
may be a half-shell bracelet consisting of two semicircular sections or a segmented bracelet consisting of a large number of
individual sections.
braze—(1) a bond produced as the result of heating an assembly to the brazing temperature greater than 450 °C [840 °F] and
less than the solidus temperature of the base metal using a brazing filler metal distributed and retained between the closely fitted
faying surfaces of the joint by capillary action. (2) the act of creating a braze.
breakdown potential—the least noble potential at which pitting or crevice corrosion, or both, will initiate and propagate in a
specific environment.
Brinell hardness—hardness value, measured in accordance with ISO 6506-1 or Test Method E10, using a 1 mm to 10 mm
diameter tungsten carbide ball and a force of approximately 9.807 N to 29.420 N (1 kgf to 3000 kgf).
brittle fracture—fracture that occurs with little or no plastic deformation of the material. [contrast with ductile fracture]
brush-off blast cleaned surface—an abrasive blast cleaned steel surface that is free of all visible contaminants and foreign
matter but may have some tightly adherent mill scale, rust, or coating. [See NACE No. 4/SSPC-SP 7 for detailed specification.]
burnish—process of smoothing surfaces using frictional contact between the material and some other hard pieces of hard
material (for example, hardened steel balls).
calcareous coating—a layer consisting of calcium carbonate and other salts deposited on the surface. When the surface is
cathodically polarized as in cathodic protection, this layer is the result of the increased pH adjacent to the protected surface.
calcareous deposit—see calcareous coating.
carbon steel—alloy of carbon and iron containing up to 2 mass percent carbon and up to 1.65 mass percent manganese and
residual quantities of other elements, except those intentionally added in specific quantities for deoxidation (usually silicon
and/or aluminum).
carburizing—the absorption and diffusion of carbon in iron or an iron-based alloy in contact with a suitable carbonaceous
environment at elevated temperature.
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case hardening—hardening a ferrous alloy so that the outer portion, or case, is made substantially harder than the inner portion,
or core. Typical processes are carburizing, cyaniding, carbonitriding, nitriding, induction hardening, and flame hardening.
casein paint—water-thinned paint with vehicle derived from milk.
cast iron—a generic term for a large family of cast ferrous alloys in which the carbon content exceeds the solubility of carbon
in austenite at the eutectic temperature, or about 2 mass percent. Most cast irons also contain silicon, and may contain other
alloying elements and impurities.
casting—(1) a component formed at or near its finished shape by the solidification of liquid material in a mold; (2) the creation
of such a component.
catalyst—a chemical substance, usually present in small amounts relative to the reactants, that increases the rate at which a
chemical reaction (for example, curing) would otherwise occur, but is not consumed in the reaction.
cathode—the electrode of an electrochemical cell at which reduction is the principal reaction. (Electrons flow toward the
cathode in the external circuit.)
cathodic corrosion—corrosion of a metal when it is a cathode, usually caused by the reaction of an amphoteric metal with the
alkaline products of electrolysis.
cathodic disbondment—the destruction of adhesion between a coating and the coated surface caused by products of a cathodic
reaction.
cathodic inhibitor—a corrosion inhibitor whose primary action is to reduce the rate of the cathodic reaction, producing a
negative shift in corrosion potential.
cathodic polarization—(1) the change of electrode potential caused by a cathodic current flowing across the electrode/
electrolyte interface. (2) a forced active (negative) shift in electrode potential. [See polarization.]
cathodic protection—a technique to reduce the corrosion rate of a metal surface by making that surface the cathode of an
electrochemical cell.
catholyte—the electrolyte adjacent to the cathode of an electrochemical cell.
cation—a positively charged ion.
caustic cracking—cracking of a metal or alloy under the combined action of tensile stress and corrosion in the presence of a
strongly basic solution (for example, sodium hydroxide, potassium hydroxide).
caustic embrittlement—an obsolete term referring to caustic cracking.
cavitation—the formation and rapid collapse of cavities or bubbles of vapor or gas within a liquid resulting from mechanical
or hydrodynamic forces.
cavitation-corrosion—the conjoint action of cavitation and corrosion.
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cavitation damage—the degradation of a solid body resulting from its exposure to cavitation. (This may include loss of
material, surface deformation, or changes in properties or appearance.)
cavitation-erosion—the conjoint action of cavitation and erosion.
cell—see electrochemical cell.
cementation—the introduction of one or more elements into the surface layer of a metal or alloy by diffusion at high
temperature. (Examples of cementation include carburizing [introduction of carbon], nitriding [introduction of nitrogen], and
chromizing [introduction of chromium].)
cementite—iron carbide (Fe C) when referred to as a microstructural constituent of steel.
chalking—the development of loose, removable powder (pigment) at the surface of an organic coating, usually caused by
weathering.
checking—the development of slight breaks in a coating that do not penetrate to the underlying surface.
chemical conversion coating—an adherent, reaction-product layer on a metal surface formed in situ by reaction with a suitable
chemical, used for protective, decorative, or functional purposes. (It is often used to provide greater corrosion resistance or
prepare the surface prior to the application of an organic coating.)
chevron pattern—a V-shaped pattern on a fatigue or brittle-fracture surface. The pattern can also be one of straight radial lines
on cylindrical specimens.
chipping—(1) removing coating and surface contaminants from a substrate in small pieces by cutting, striking, or applying
mechanical force; (2) a failure mechanism in which small pieces or fragments of a material or coating are removed by
mechanical damage, loss of adhesion, or both. [contrast with peeling]
chloride stress corrosion cracking—cracking of a metal under the combined action of tensile stress and corrosion in the
presence of an electrolyte containing dissolved chlorides.
cleavage fracture—fracture that occurs along planes determined by the crystal structure of the material. (It is typically
associated with a brittle fracture.)
coat—one layer of a coating system applied to a surface in a single continuous application to form a uniform film when dry.
coating—(1) a liquid, liquefiable, or mastic composition that, after application to a surface, is converted into a solid protective,
decorative, or functional adherent film. (2) (in a more general sense) a thin layer of solid material on a surface that provides
improved protective, decorative, or functional properties.
coating system—the complete number and types of coats applied to a substrate in a predetermined order. (When used in a
broader sense, surface preparation, pretreatments, dry film thickness, and manner of application are included.)
cold cracking—cracking of a weld during or after cooling to ambient temperature, sometimes after a considerable time delay.
(It usually occurs at temperatures less than 205 °C [400 °F] for metals, and less than the glass transition temperature for plastics.)
cold lap—a linear discontinuity with rounded edges at exposed surfaces that is caused by solidification of the meniscus of a
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partially cast metal or alloy (for example, an anode used for cathodic protection) as a result of interrupted flow of the casting
stream or the joining of two casting streams at too low a temperature.
cold shut—horizontal surface discontinuity caused by solidification of a portion of a meniscus during the progressive filling of
a mold, which is later covered with more solidifying metal as the molten metal level rises. Cold shuts generally occur at corners
remote from the point of pour.
cold working—deforming metal plastically under conditions of temperature and strain rate that induce strain hardening, usually,
but not necessarily, performed at room temperature [contrast with hot working]
commercial blast cleaned surface—an abrasive blast cleaned steel surface that is free of all visible contaminants and foreign
matter but may have some random staining on no more than 33 percent of the surface area. [See NACE No. 3/SSPC-SP 6 for
detailed specification.]
compressive strength—the maximum compressive stress a material is capable of withstanding without sustaining permanent
deformation.
concentration cell—an electrochemical cell, the electromotive force of which is caused by a difference in concentration of some
component in the electrolyte. (This difference leads to the formation of discrete cathodic and anodic regions.)
concentration polarization—that portion of polarization of an electrochemical cell produced by concentration changes
resulting from current flowing through the electrolyte.
conductive coating—(1) a coating that conducts electricity. (2) an electrically conductive, mastic-like material used as an
impressed current anode on reinforced concrete surfaces.
conductive concrete—a highly conductive cement-based mixture containing coarse and fine coke and other material used as an
impressed current anode on reinforced concrete surfaces.
conductivity—(1) a measure of the ability of a material to conduct an electric charge. (2) the current transferred across a
material (for example, coating) per unit area per unit potential gradient. (Conductivity is the reciprocal of resistivity.)
contact corrosion—see galvanic corrosion.
continuity bond—a connection, usually metallic, that provides electrical continuity between structures that can conduct
electricity.
continuous anode—a single anode with no electrical discontinuities.
conversion coating—see chemical conversion coating.
copper sulfate test—(1) a test method in which a solution of copper sulfate, and possibly other ingredients, in water is swabbed
onto the surface of certain metals to determine the presence of metals more active (anodic) than copper. (2) a spot test method
in which a 5 to 10 percent solution of copper sulfate in water is swabbed onto a steel surface to determine whether mill scale
is present. (The appearance of copper indicates that mill scale is not present.)
corrosion—the deterioration of a material, usually a metal, that results from a chemical or electrochemical reaction with its
environment.
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corrosion-inhibitive pigment—a pigment that has the property of minimizing corrosion of the metal substrate to which the
coating is applied by directly reducing the anodic or cathodic reactions, or both [contrast with sacrificial pigment and barrier
pigment].
corrosion fatigue—the process wherein a metal fractures prematurely under conditions of simultaneous corrosion and repeated
cyclic loading at lower stress levels or fewer cycles than would be required to cause fatigue of that metal in the absence of the
corrosive environment.
corrosion fatigue strength—the maximum repeated stress that can be endured by a metal without fracture under definite
conditions of corrosion and cyclic loading for a specific number of stress cycles and a specified period of time.
corrosion inhibitor—a chemical substance or combination of substances that, when present in the proper concentration and
forms in the environment, reduces the corrosion rate.
corrosion potential—(represented by the symbol E ) the potential of a corroding surface in an electrolyte measured under
corr
open-circuit conditions relative to a reference electrode. [also known as electrochemical corrosion potential,free corrosion
potential,open-circuit potential ]
corrosion rate—the time rate of change of corrosion. (It is typically expressed as mass loss per unit area per unit time,
penetration per unit time, etc.)
corrosion resistance—ability of a material, usually a metal, to withstand corrosion in a given environment.
corrosion under insulation—deterioration that occurs on an insulated component such as a pipe, vessel, or structural member
as a result of water or other corrodents being trapped against the component by the insulating material.
DISCUSSION—
Insulating materials may include, but are not limited to, thermal insulation, electrical insulation, acoustic insulation, and fireproofing.
corrosiveness—the tendency of an environment to cause corrosion.
counter electrode—the electrode in an electrochemical cell that is used to transfer current to or from a working electrode.
counterpoise—a conductor or system of conductors arranged beneath a power line, located on, above, or most frequently, below
the surface of the earth and connected to the footings of the towers or poles supporting the power line.
couple—see galvanic couple.
coupon—a portion of a material or sample, usually flat, but occasionally curved or cylindrical, from which one or more
specimens can be taken for testing.
crack—(1) a partial split or break. (2) a split or break in a coating that penetrates to the substrate.
cracking—fracture of a material along a path that produces a linear discontinuity (without complete separation).
crater—(1) a metal surface anomaly consisting of a bowl-shaped cavity with the minimum dimension at the opening greater
than the depth. [contrast with pit] (2) a small, rounded dish or bowl-like depression in a wet-applied coating. [contrast with fish
eye]
crazing—a network of checks or cracks appearing on the surface of a coating.
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creep—time-dependent strain occurring under stress.
creep strength—that stress which, when applied to a material at a specific temperature, will cause a specified amount of
elongation in a specified time.
crevice corrosion—localized corrosion of a metal or alloy surface at, or immediately adjacent to, an area that is shielded from
full exposure to the environment because of close proximity of the metal or alloy to the surface of another material or an adjacent
surface of the same metal or alloy.
critical anodic current density—the maximum anodic current density observed in the active region for a metal or alloy
electrode that exhibits active-passive behavior in an environment.
critical humidity—the relative humidity above which the atmospheric corrosion rate of a specific metal or alloy increases
sharply.
critical pitting potential—(represented by the symbol E or E ) the least noble potential at which pitting corrosion will initiate
p pp
and propagate in a specific environment. [See breakdown potential.]
curing—process of developing the intended properties of a coating or other material (for example, resin) over a period of time.
curing agent—a chemical substance used for curing a coating or other material (for example, resin). [also referred to as
hardener]
curing time—the minimum period between application and the time at which the applied material attains its intended physical
properties.
current—(1) a flow of electric charge. (2) the amount of electric charge flowing past a specified circuit point per unit time,
measured in the direction of net transport of positive charges. (In a metallic conductor, this is the opposite direction of the
electron flow.)
current density—the electric current flowing to or from a unit area of an electrode surface.
current efficiency—the ratio of the electrochemical equivalent current density for a specific reaction to the total applied current
density.
DC decoupling device—a device used in electrical circuits that allows the flow of alternating current in both directions and
stops or substantially reduces the flow of direct current.
deactivation—the process of prior removal of the active corrosive constituents, usually oxygen, from a corrosive liquid by
controlled corrosion of expendable metal or by other chemical means, thereby making the liquid less corrosive.
dealloying—a corrosion process whereby one constituent of an alloy is preferentially removed, leaving an altered residual
structure. [also known as parting,selective dissolution, or selective leaching]
decomposition potential—the potential of an electrode surface at which the electrolyte, or a component thereof, decomposes
by electrolysis.
decomposition voltage—see decomposition potential.
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deep groundbed—one or more anodes installed vertically at a nominal depth of 15 m (50 ft) or more below the earth’s surface
in a drilled hole for the purpose of supplying cathodic protection current.
delamination—(1) separation of layers in a material. (2) a separation between one or more coats from another coat within a
coating system. [contrast with disbondment] (3) a separation of the concrete (usually in layers) from the reinforcing steel at their
interface, usually as a result of corrosion.
delayed cracking—(1) cracking in a metal occurring after plating or pickling, sometimes after a considerable time delay. (2)
not a preferred term for cold cracking.
depolarization—(not a preferred term) the removal of factors resisting the current flow in an electrochemical cell. [See
polarization.]
deposit corrosion—localized corrosion under or around a deposit or collection of material on a metal surface. [also called
poultice corrosion] [See also crevice corrosion.]
dezincification—dealloying that results in the selective removal of zinc from copper-zinc alloys.
dielectric coating—a coating that does not conduct electricity.
dielectric shield—an electrically nonconductive material, such as a coating, sheet or pipe, that is placed between an anode and
an adjacent cathode, usually on the cathode, to improve current distribution in a cathodic protection system.
differential aeration cell—a concentration cell caused by differences in oxygen concentration along the surface of a metal in
an electrolyte. [See concentration cell.]
diffusion-limited current density—the current density that corresponds to the maximum transfer rate that a particular species
can sustain because of the limitation of diffusion [often referred to as limiting current density]
disbondment—the loss of adhesion between a coating and the substrate.
discontinuity—(1) an interruption in the normal physical structure or configuration of a coating such as cracks, laps, seams,
inclusions, porosity, or holidays. (A discontinuity does not necessarily affect the usefulness of the coating.) (2) a condition in
which the electrical path through a structure is interrupted by a device that acts as a dielectric or insulating fitting.
dissimilar metals—different metals that could form an anode-cathode relationship in an electrolyte when connected by an
electron-conducting (usually metallic) path.
double layer—the interface between an electrode or a suspended particle and an electrolyte created by charge-charge interaction
leading to an alignment of oppositely charged ions at the surface of the electrode or particle. The simplest model is represented
by a parallel plate condenser.
doubler plate—an additional plate or thickness of metal used to provide extra strength or thickness to a structure locally (for
example, at the point of anode attachment to an offshore structure).
drainage—conduction of electric current from an underground or submerged metallic structure by means of a metallic
conductor.
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driving potential—difference in potential between the anode and the steel structure.
dry film thickness—the thickness of a dried film, coating, or membrane.
dry spray—a rough, powdery noncoherent film produced when atomized coating particles partially dry before reaching the
surface.
dry to handle—stage of drying or curing of an applied coating at which time the coated object can be carefully handled without
damage.
dry to recoat—stage of drying or curing of an applied coating at which time a subsequent coat can be applied satisfactorily.
dry to touch—stage of drying or curing of an applied coating at which time it no longer adheres to a finger that is lightly touched
or rubbed across the surface and does not show a fingerprint at the point of contact.
drying—the process in which a liquid film is converted to a solid film by evaporation of volatile components.
drying oil—an oil capable of conversion from a liquid to a solid by slow reaction with oxygen in the air.
drying time—minimum time required for an applied coating to reach the desired stage of drying or curing.
ductile cast iron—cast iron that has been treated while molten with an element (usually magnesium or cerium) that spheroidizes
the graphite. [also called nodular cast iron].
ductile fracture—fracture that occurs with appreciable plastic deformation of the material. [contrast with brittle fracture]
ductility—the ability of a material to withstand plastic deformation prior to fracture. (It is usually measured by the permanent
elongation or reduction in the cross-sectional area of a fractured tensile test specimen.)
duplex stainless steel—stainless steel whose microstructure at room temperature consists primarily of a mixture of austenite and
ferrite. [also called austenitic/ferritic stainless steel].
elastic deformation—changes of dimensions of a material upon the application of a stress within the elastic range. Following
the release of an elastic stress, the material returns to its original dimensions without any permanent deformation.
elasticity—the property of a material that allows it to recover its original dimensions following deformation by a stress below
its elastic limit.
elastic limit—the maximum stress to which a material may be subjected without retention of any permanent deformation after
the stress is removed.
electrical interference—any electrical disturbance on a metallic structure in contact with an electrolyte caused by stray
current(s).
electrical isolation—the condition of being electrically separated from other metallic structures or the environment.
electrochemical admittance—the reciprocal of the electrochemical impedance, ΔI/ΔE.
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electrochemical cell—(1) an electrochemical reaction involving two half reactions, one of which involves oxidation of the
reactant (product) and the other of which involves reduction of the product (reactant). (The equilibrium potential of the
electrochemical cell can be calculated from the change in free energy for the overall electrochemical reaction. The equilibrium
potential of the electrochemical cell can be measured by separating the oxidation and reduction half reactions into individual
compartments and measuring the voltage that develops between them under conditions that virtually no charge passes between
them.) [thermodynamic use] (2) an electrochemical system consisting of an anode and a cathode in metallic contact and
immersed in an electrolyte. (The anode and cathode may be different metals or dissimilar areas on the same metal surface.)
[common use]
electrochemical corrosion potential—see corrosion potential.
electrochemical equivalent—the mass of an element or group of elements oxidized or reduced at 100 percent efficiency by the
passage of a unit quantity of charge such as a Faraday (96,485 coulombs), ampere-hour, or coulomb.
electrochemical impedance—the frequency dependent, complex valued proportionality factor, ΔI/ΔE, between the applied
potential (or current) and the response current (or potential) in an electrochemical cell. This factor becomes the impedance when
the perturbation and response are related linearly (the factor value is independent of the perturbation magnitude) and the
response is caused only by the perturbation. The value may be related to the corrosion rate when the measurement is made at
the corrosion potential.
electrochemical noise—fluctuations of potential or current, or both, originating from uncontrolled variations in a corrosion
process.
electrochemical potential—the partial derivative of the total electrochemical free energy of the system with respect to the
number of moles of the constituent in a solution when all other factors are constant. (Analogous to the chemical potential of the
constituent except that it includes the electrical as well as the chemical contributions to the free energy.)
electrode—a material that conducts electrons, is used to establish contact with an electrolyte, and through which current is
transferred to or from an electrolyte.
electrode potential—the potential of an electrode in an electrolyte as measured against a reference electrode.
electrokinetic potential—a potential difference in a solution caused by residual, unbalanced charge distribution in the adjoining
solution, producing a double layer. (The electrokinetic potential is different from the electrode potential in that it occurs
exclusively in the solution phase. This potential represents the reversible work necessary to bring a unit charge from infinity in
the solution up to the interface in question but not through the interface.) [also known as zeta potential]
electrolysis—production of chemical changes of the electrolyte by the current flowing through an electrochemical cell.
electrolyte—a chemical substance containing ions that migrate in an electric field.
electrolytic corrosion—not a proper term, but sometimes incorrectly used to refer to galvanic corrosion,stray-current
corrosion, or any form of electrochemical corrosion.
electrolytic cleaning—a process for removing soil, scale, or corrosion products from a metal surface by subjecting the metal
as an electrode to an electric current in an electrolytic bath.
electromotive force series—a list of elements arranged according to their standard electrode potentials, the sign being positive
for elements whose potentials are more noble than hydrogen such as gold and negative for those more active than hydrogen such
as zinc. [not to be confused with galvanic series]
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electro-osmosis—the migration of water through a semipermeable membrane as a result of a potential difference caused by the
flow of electric charge through the membrane.
ellipsometry—an optical technique wherein plane-polarized light is focused on a surface and the reflected beam is analyzed to
determine the phase shift of the components of the light to provide information on the properties of films that may be present
on the surface.
embrittlement—reduction of ductility, or toughness, or both, of a material (usually a metal or alloy).
EMF series—see electromotive force series.
enamel—(1) a paint that dries to a hard, glossy surface. (2) a coating that is characterized by an ability to form a smooth, durable
film.
end effect—the more rapid loss of anode material at the end of an anode, compared with other surfaces of the anode, resulting
from higher current density.
endurance limit—the maximum stress that a material can withstand for an infinitely large number of fatigue cycles.
environment—the surroundings or conditions (physical, chemical, mechanical) in which a material exists.
environmental cracking—cracking of a material wherein an interaction with its environment is a causative factor in
conjunction with tensile stress, often resulting in brittle fracture of an otherwise ductile material. [also known as see
environmentally assisted crackingcracking.]
DISCUSSION—
Environmental cracking is a general term that includes the terms listed below. The definitions of these terms are listed elsewhere in this document:
caustic cracking,chloride stress corrosion cracking,corrosion fatigue,hydrogen embrittlement,hydrogen-induced cracking (stepwise cracking),
hydrogen stress cracking,liquid metal cracking,stress corrosion cracking,sulfide stress cracking.
DISCUSSION—
The following terms have been used in the past in connection with environmental cracking but are now obsolete and should not be used: caustic
embrittlement,delayed cracking,liquid metal embrittlement,season cracking,static fatigue,sulfide corrosion cracking,sulfide stress corrosion
cracking.
environmentally assisted cracking—seecracking environmental cracking.of a material wherein an interaction with its
environment is a causative factor in conjunction with tensile stress, often resulting in brittle fracture of an otherwise ductile
material.
epoxy—type of resin formed by the reaction of aliphatic or aromatic polyols (such as bisphenol) with epichlorohydrin and
characterized by the presence of reactive oxirane end groups.
equilibrium potential—the potential of an electrode in an electrolyte at which the forward rate of a given reaction is exactly
equal to the reverse rate. (The equilibrium potential can only be defined with respect to a specific electrochemical reaction.) [also
known as reversible potential]
erosion—the progressive loss of material from a solid surface resulting from mechanical interaction between that surface and
a fluid, a multicomponent fluid, or solid particles carried with the fluid.
erosion-corrosion—a conjoint action involving erosion and corrosion in the presence of a moving corrosive fluid or a material
moving through the fluid, leading to accelerated loss of material.
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exchange current density—the rate of charge transfer per unit area when an electrode reaches dynamic equilibrium (at its
reversible potential) in a solution; that is, the rate of anodic charge transfer (oxidation) is exactly equal to the rate of cathodic
charge transfer (reduction).
exfoliation corrosion—subsurface corrosion that proceeds laterally from the sites of initiation along planes parallel to the
surface forming corrosion products that force metal away from the body of the material, giving rise to a layered appearance
resembling the pages of a book.
external circuit—the wires, connectors, measuring devices, current sources, etc., that are used to bring about or measure the
desired electrical conditions within an electrochemical cell. It is this portion of the cell through which electrons travel.
fatigue—the process of progressive localized permanent structural change occurring in a material subjected to fluctuating
stresses less than the ultimate tensile strength of the material that may culminate in cracks or complete fracture after a sufficient
number of fluctuations.
fatigue strength—the maximum stress that can be sustained for a specified number of
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