ASTM G111-97(2018)

Standard Guide for Corrosion Tests in High Temperature or High Pressure Environment, or Both

SIGNIFICANCE AND USE
5.1 HP and HTHP corrosion tests are commonly used to evaluate the corrosion performance of metallic materials under conditions that attempt to simulate service conditions that involve HP or HTHP in combination with service environments. Examples of service environments where HP and HTHP corrosion tests have been utilized include chemical processing, petroleum production and refining, food processing, pressurized cooling water, electric power systems and aerospace propulsion.  
5.2 For the applications of corrosion testing listed in 5.1, the service involves handling corrosive and potentially hazardous media under conditions of high pressure or high temperature, or both. The temperature and pressure usually enter directly into the severity of the corrosion process. Consequently, the laboratory evaluation of corrosion severity cannot be performed in conventional low pressure glassware without making potentially invalid assumptions as to the potential effects of high temperature and pressure on corrosion severity.  
5.3 Therefore, there is a substantial need to provide standardized methods by which corrosion testing can be performed under HP and HTHP. In many cases, however, the standards used for exposure of specimens in conventional low pressure glassware experiments cannot be followed due to the limitations of access, volume and visibility arising from the construction of high pressure test cells. This guide refers to existing corrosion standards and practices as applicable and then goes further in areas where specific guidelines for performing HP and HTHP corrosion testing are needed.
SCOPE
1.1 This guide covers procedures, specimens, and equipment for conducting laboratory corrosion tests on metallic materials under conditions of high pressure (HP) or the combination of high temperature and high pressure (HTHP). See 3.2 for definitions of high pressure and temperature.  
1.2 Tests conducted under HP or HTHP by their nature have special requirements. This guide establishes the basic considerations that are necessary when these conditions must be incorporated into laboratory corrosion tests.  
1.3 The procedures and methods in this guide are applicable for conducting mass loss corrosion, localized corrosion, and electrochemical tests as well as for use in environmentally induced cracking tests that need to be conducted under HP or HTHP conditions.  
1.4 The primary purpose for this guide is to promote consistency of corrosion test results. Furthermore, this guide will aid in the comparison of corrosion data between laboratories or testing organizations that utilize different equipment.  
1.5 The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only.  
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.7 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: Historical
• Publication Date: 30-Sep-2018
• ICS: 77.060 - Corrosion of metals
• Technical Committee: G01 - Corrosion of Metals
• Drafting Committee: G01.05 - Laboratory Corrosion Tests

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: G111 − 97 (Reapproved 2018)
Standard Guide for
Corrosion Tests in High Temperature or High Pressure
Environment, or Both
This standard is issued under the fixed designation G111; 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 mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
1.1 This guide covers procedures, specimens, and equip-
ment for conducting laboratory corrosion tests on metallic
2. Referenced Documents
materials under conditions of high pressure (HP) or the
2.1 ASTM Standards:
combination of high temperature and high pressure (HTHP).
E8/E8M Test Methods for Tension Testing of Metallic Ma-
See 3.2 for definitions of high pressure and temperature.
terials
1.2 Tests conducted under HPor HTHPby their nature have
G1 Practice for Preparing, Cleaning, and Evaluating Corro-
special requirements. This guide establishes the basic consid-
sion Test Specimens
erations that are necessary when these conditions must be
G3 Practice for Conventions Applicable to Electrochemical
incorporated into laboratory corrosion tests.
Measurements in Corrosion Testing
1.3 The procedures and methods in this guide are applicable G5 Reference Test Method for Making Potentiodynamic
for conducting mass loss corrosion, localized corrosion, and Anodic Polarization Measurements
electrochemical tests as well as for use in environmentally G15 Terminology Relating to Corrosion and Corrosion Test-
induced cracking tests that need to be conducted under HP or ing (Withdrawn 2010)
G30 Practice for Making and Using U-Bend Stress-
HTHP conditions.
Corrosion Test Specimens
1.4 The primary purpose for this guide is to promote
G31 Guide for Laboratory Immersion Corrosion Testing of
consistency of corrosion test results. Furthermore, this guide
Metals
will aid in the comparison of corrosion data between labora-
G34 Test Method for Exfoliation Corrosion Susceptibility in
tories or testing organizations that utilize different equipment.
2XXX and 7XXX Series Aluminum Alloys (EXCO Test)
1.5 The values stated in SI units are to be regarded as
G38 Practice for Making and Using C-Ring Stress-
standard. The values given in parentheses are for information
Corrosion Test Specimens
only.
G39 Practice for Preparation and Use of Bent-Beam Stress-
1.6 This standard does not purport to address all of the
Corrosion Test Specimens
safety concerns, if any, associated with its use. It is the G46 Guide for Examination and Evaluation of Pitting Cor-
responsibility of the user of this standard to establish appro-
rosion
priate safety, health, and environmental practices and deter- G49 Practice for Preparation and Use of Direct Tension
mine the applicability of regulatory limitations prior to use.
Stress-Corrosion Test Specimens
1.7 This international standard was developed in accor- G59 Test Method for Conducting Potentiodynamic Polariza-
dance with internationally recognized principles on standard-
tion Resistance Measurements
ization established in the Decision on Principles for the G78 Guide for Crevice Corrosion Testing of Iron-Base and
Development of International Standards, Guides and Recom-
Nickel-Base Stainless Alloys in Seawater and Other
1 2
This guide is under the jurisdiction ofASTM Committee G01 on Corrosion of For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Metals and is the direct responsibility of Subcommittee G01.05 on Laboratory contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Corrosion Tests. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Oct. 1, 2018. Published November 2018. Originally the ASTM website.
approved in 1992. Last previous edition approved in 2013 as G111 – 97 (2013). The last approved version of this historical standard is referenced on
DOI: 10.1520/G0111-97R18. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
G111 − 97 (2018)
Chloride-Containing Aqueous Environments existing corrosion standards and practices as applicable and
G106 Practice for Verification of Algorithm and Equipment then goes further in areas where specific guidelines for
for Electrochemical Impedance Measurements performing HP and HTHP corrosion testing are needed.
3. Terminology
6. Apparatus
3.1 Definitions—ThedefinitionsoftermsgiveninTerminol-
6.1 The test cell shall be constructed to applicable standards
ogy G15 shall be considered as applying to this guide.
and codes so that it will have an adequate pressure rating to
3.2 Definitions of Terms Specific to This Standard: safely handle the test pressure.
3.2.1 high pressure—a pressure above ambient atmospheric
6.2 The test cell shall be made of materials that are
pressure that cannot be contained in normal laboratory glass-
corrosion resistant and effectively non-reactive with the test
ware. Typically, this is greater than 0.07 MPa (10 psig).
environment.
3.2.2 high temperature—temperatures above ambient labo-
6.2.1 The term effectively non-reactive shall mean that the
ratory temperature where sustained heating of the environment test cell shall be free of significant mass loss or localized
is required.
corrosion, SCC or other embrittlement phenomena in the test
environment, not contaminate the test environment with cor-
4. Summary of Guide
rosion or other reaction products, and not consume or absorb
4.1 This guide describes the use of corrosion coupons, reactive chemical species from the test environment.
stressed SCC specimens, and electrochemical electrodes in HP
6.3 The test cell shall have a seal mechanism that can
andHTHPenvironments.Italsoincludesguidelinesfortheuse
withstand both the pressures, temperatures, and corrosive
of high pressure test cells with these specimens to conduct
environment to be used in the test. Periodic hydrostatic testing
reproducible, accurate corrosion test data.
of the test cell is recommended to ensure pressure capabilities.
4.2 Typically, HP and HPHT tests involve exposure of test
6.4 The test cell shall be designed to have the necessary
specimens to a liquid (aqueous or non-aqueous), gaseous or
inlet and outlet ports to allow the test environment to be
multiphase environment, or both, in an appropriate test cell.
established in a controllable manner, monitored and sampled
Thetestcellmustbeabletoresistcorrosionandenvironmental
during the exposure period, released in a controlled manner at
cracking in the test environment while containing the
the completion of the test, and if over temperature or pressure
pressurized, heated environment. Furthermore, the test speci-
conditions may occur, adequate over pressure release and over
mens in the HPor HPHTtest, or both, can be exposed in either
temperature control equipment should be utilized.
stressed or unstressed condition in either the free corroding
6.5 In cases where external loading fixtures are used for
state or under electrochemical polarization.
stressing specimens in the HP and HTHP test environment,
5. Significance and Use specially designed feed-throughs shall be used which provide
for a minimum of friction force.
5.1 HP and HTHP corrosion tests are commonly used to
evaluate the corrosion performance of metallic materials under 6.6 Test cell feed-throughs required for external stressing
may be designed to balance the internal pressure in the test
conditions that attempt to simulate service conditions that
involve HP or HTHP in combination with service environ- vessel.
ments.ExamplesofserviceenvironmentswhereHPandHTHP
6.7 Any frictional or pressure forces (or thermal expansion)
corrosion tests have been utilized include chemical processing,
acting on the specimen through the stressing fixtures must be
petroleum production and refining, food processing, pressur-
taken into account when determining the actual load on the
ized cooling water, electric power systems and aerospace
specimen.
propulsion.
6.8 Stressing and electrode feed-throughs shall be designed
5.2 Fortheapplicationsofcorrosiontestinglistedin5.1,the
sothattheelectrodesorstressingrodsandspecimenscannotbe
service involves handling corrosive and potentially hazardous
ejected from the test cell under pressure. Furthermore, they
media under conditions of high pressure or high temperature,
shall provide for electrical isolation of the specimen from the
or both. The temperature and pressure usually enter directly
test cell unless galvanic coupling is specifically desired.
into the severity of the corrosion process. Consequently, the
6.9 Gripping devices shall be designed such that they are in
laboratory evaluation of corrosion severity cannot be per-
compliance with Test Method E8/E8M where application of
formedinconventionallowpressureglasswarewithoutmaking
load to the specimen is required.
potentially invalid assumptions as to the potential effects of
high temperature and pressure on corrosion severity.
7. Reagents
5.3 Therefore, there is a substantial need to provide stan-
7.1 In corrosion testing, providing a reproducible chemical
dardized methods by which corrosion testing can be performed
environmentinwhichtoexposethecorrosiontestspecimensis
under HP and HTHP. In many cases, however, the standards
necessary.
used for exposure of specimens in conventional low pressure
glassware experiments cannot be followed due to the limita- 7.2 Incaseswherethetestenvironmentisestablishedbythe
tions of access, volume and visibility arising from the con- mixing of chemicals in the laboratory, chemicals of reagent
struction of high pressure test cells. This guide refers to grade purity with known contaminant levels are recommended.
G111 − 97 (2018)
Simulations of service environments can be formulated in 8.3.1 Both self stressed and externally stressed specimens
which laboratory corrosion tests can be conducted. are acceptable for testing at HP and HTHP. Methods for the
fabrication and use of appropriate stressed specimens are given
7.3 In HP/HTHP corrosion testing, a common practice is to
inthereferenceddocuments.Theseincludetension,bentbeam,
conduct tests in environments that have been sampled and
C-ring, and U-bend specimens in accordance with Practices
retrieved from field or plant locations. In both cases described
G49, G39, G38, and G30, respectively. Fracture mechanics
in 7.2 and 7.3, detailed information as to the chemical
specimens can also be accommodated.
composition of the environment should be obtained. Particular
8.3.2 For similar reasons given in 8.2, when testing multiple
attention should be given to the levels of impurities and
specimens, it is recommended that the size of the specimens be
contaminants that may be in the environment. Furthermore,
restricted to the smallest applicable specimen provided for
under some conditions, these environments may be prone to
under the appropriate standards.
changes after sampling or during testing which can affect the
8.3.3 Due to the limited access of the specimens in HP and
corrosion test results.
HTHP tests, self stressed specimens are usually more conve-
7.4 Inmanycases,thetestcellsusedtoconductHPtestsare
nient than specimens that require external stressing fixtures.
limited in volume and may not be designed to accommodate
8.3.4 In cases such as direct tension and fracture mechanics
replenishment of the environment. Therefore, monitoring the
tests,useofexternalloadingframesandfixturesinconjunction
chemical composition of the environment during the exposure
with HP and HTHP corrosion tests may be desirable. In these
may be necessary to identify if depletion of reactive constitu-
cases, take both the frictional (sealing) forces and pressure
ents or concentration of constituents has occurred. In some
forces acting on the specimens into account when determining
cases, replenishment or changing of the test environment may
the effect of applied stress.
be necessary so that a valid corrosion test can be conducted.
8.4 Electrochemical Electrodes:
7.5 In all cases, it is recommended that the test environment
8.4.1 Prepare electrodes for use in HP and HTHP corrosion
be fully documented with respect to its chemical composition.
studies as described in Practice G3, Test Method G5, and
Practices G59 and G106.
8. Test Specimens
8.4.2 Cylindrical electrode specimens where only the lower
portion of the electrode is exposed to the liquid phase of test
8.1 Preparation of Specimens:
environment and where the electrical connections are made
8.1.1 The primary objective is to prepare a reproducible
externally to the test cell are a convenient geometry. Care must
metallic surface with an absolute minimum of coldworking
be taken to electrically isolate the electrodes from the test cell.
followed by cleaning and degreasing.
Other electrode geometries and designs may be used that
8.1.2 Since test cells for HP and HTHP tests are usually of
facilitate feed-through and electrical isolation.
metallic construction, care must be taken to electrically isolate
8.4.3 A critical portion of the HP or HTHP electrochemical
the specimens from the test cell unless galvanic coupling is
system is the design and construction of the reference elec-
specifically desired in the test. In cases where the test cell is
trode. It is common to use external reference cells that use
used as a member of a galvanic couple, care must be taken to
stable reference systems such as Ag/AgCl or other stable
ensure that the galvanic action (anodic or cathodic) does not
electrochemical reference system that can be enclosed in a
degrade the integrity of the test cell.
separate pressure containing compartment. This cell is then
8.2 Corrosion Specimens:
connected to the test cell via a salt bridge and is pressure
8.2.1 Prepare specimens used in HP or HTHP corrosion
balanced with the test cell to minimize ingress of contaminants
testsinaccordancewithPracticesG1andG31.Commonly,test
into either the test cell or the reference electrode.Alternatively,
cells used for HP and HTHP exposure tests are restricted in
an inert or corroding metal electrode can be used as a
volume. The available volume in the test cell often decreases
pseudo-reference electrode in some cases. Examples of such
with increasing pressure rating. Therefore, it is frequently
pseudo-reference electrodes include platinum, graphite, or
necessary to restrict the size and surface area of corrosion
other metal with known stable corrosion potential. However,
coupons used in
...

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: G111 − 97 (Reapproved 2013) G111 − 97 (Reapproved 2018)
Standard Guide for
Corrosion Tests in High Temperature or High Pressure
Environment, or Both
This standard is issued under the fixed designation G111; 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 guide covers procedures, specimens, and equipment for conducting laboratory corrosion tests on metallic materials
under conditions of high pressure (HP) or the combination of high temperature and high pressure (HTHP). See 3.2 for definitions
of high pressure and temperature.
1.2 Tests conducted under HP or HTHP by their nature have special requirements. This guide establishes the basic
considerations that are necessary when these conditions must be incorporated into laboratory corrosion tests.
1.3 The procedures and methods in this guide are applicable for conducting mass loss corrosion, localized corrosion, and
electrochemical tests as well as for use in environmentally induced cracking tests that need to be conducted under HP or HTHP
conditions.
1.4 The primary purpose for this guide is to promote consistency of corrosion test results. Furthermore, this guide will aid in
the comparison of corrosion data between laboratories or testing organizations that utilize different equipment.
1.5 The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.7 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:
E8E8/E8M Test Methods for Tension Testing of Metallic Materials [Metric] E0008_E0008M
G1 Practice for Preparing, Cleaning, and Evaluating Corrosion Test Specimens
G3 Practice for Conventions Applicable to Electrochemical Measurements in Corrosion Testing
G5 Reference Test Method for Making Potentiodynamic Anodic Polarization Measurements
G15 Terminology Relating to Corrosion and Corrosion Testing (Withdrawn 2010)
G30 Practice for Making and Using U-Bend Stress-Corrosion Test Specimens
G31 Guide for Laboratory Immersion Corrosion Testing of Metals
G34 Test Method for Exfoliation Corrosion Susceptibility in 2XXX and 7XXX Series Aluminum Alloys (EXCO Test)
G38 Practice for Making and Using C-Ring Stress-Corrosion Test Specimens
G39 Practice for Preparation and Use of Bent-Beam Stress-Corrosion Test Specimens
G46 Guide for Examination and Evaluation of Pitting Corrosion
G49 Practice for Preparation and Use of Direct Tension Stress-Corrosion Test Specimens
G59 Test Method for Conducting Potentiodynamic Polarization Resistance Measurements
This guide is under the jurisdiction of ASTM Committee G01 on Corrosion of Metals and is the direct responsibility of Subcommittee G01.05 on Laboratory Corrosion
Tests.
Current edition approved May 1, 2013Oct. 1, 2018. Published July 2013November 2018. Originally approved in 1992. Last previous edition approved in 20062013 as
G111G111 – 97 (2013).–97 (2006). DOI: 10.1520/G0111-97R13. 10.1520/G0111-97R18.
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.
The last approved version of this historical standard is referenced on www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
G111 − 97 (2018)
G78 Guide for Crevice Corrosion Testing of Iron-Base and Nickel-Base Stainless Alloys in Seawater and Other Chloride-
Containing Aqueous Environments
G106 Practice for Verification of Algorithm and Equipment for Electrochemical Impedance Measurements
3. Terminology
3.1 Definitions—The definitions of terms given in Terminology G15 shall be considered as applying to this guide.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 high pressure—a pressure above ambient atmospheric pressure that cannot be contained in normal laboratory glassware.
Typically, this is greater than 0.07 MPa (10 psig).
3.2.2 high temperature—temperatures above ambient laboratory temperature where sustained heating of the environment is
required.
4. Summary of Guide
4.1 This guide describes the use of corrosion coupons, stressed SCC specimens, and electrochemical electrodes in HP and
HTHP environments. It also includes guidelines for the use of high pressure test cells with these specimens to conduct
reproducible, accurate corrosion test data.
4.2 Typically, HP and HPHT tests involve exposure of test specimens to a liquid (aqueous or non-aqueous), gaseous or
multiphase environment, or both, in an appropriate test cell. The test cell must be able to resist corrosion and environmental
cracking in the test environment while containing the pressurized, heated environment. Furthermore, the test specimens in the HP
or HPHT test, or both, can be exposed in either stressed or unstressed condition in either the free corroding state or under
electrochemical polarization.
5. Significance and Use
5.1 HP and HTHP corrosion tests are commonly used to evaluate the corrosion performance of metallic materials under
conditions that attempt to simulate service conditions that involve HP or HTHP in combination with service environments.
Examples of service environments where HP and HTHP corrosion tests have been utilized include chemical processing, petroleum
production and refining, food processing, pressurized cooling water, electric power systems and aerospace propulsion.
5.2 For the applications of corrosion testing listed in 5.1, the service involves handling corrosive and potentially hazardous
media under conditions of high pressure or high temperature, or both. The temperature and pressure usually enter directly into the
severity of the corrosion process. Consequently, the laboratory evaluation of corrosion severity cannot be performed in
conventional low pressure glassware without making potentially invalid assumptions as to the potential effects of high temperature
and pressure on corrosion severity.
5.3 Therefore, there is a substantial need to provide standardized methods by which corrosion testing can be performed under
HP and HTHP. In many cases, however, the standards used for exposure of specimens in conventional low pressure glassware
experiments cannot be followed due to the limitations of access, volume and visibility arising from the construction of high
pressure test cells. This guide refers to existing corrosion standards and practices as applicable and then goes further in areas where
specific guidelines for performing HP and HTHP corrosion testing are needed.
6. Apparatus
6.1 The test cell shall be constructed to applicable standards and codes so that it will have an adequate pressure rating to safely
handle the test pressure.
6.2 The test cell shall be made of materials that are corrosion resistant and effectively non-reactive with the test environment.
6.2.1 The term effectively non-reactive shall mean that the test cell shall be free of significant mass loss or localized corrosion,
SCC or other embrittlement phenomena in the test environment, not contaminate the test environment with corrosion or other
reaction products, and not consume or absorb reactive chemical species from the test environment.
6.3 The test cell shall have a seal mechanism that can withstand both the pressures, temperatures, and corrosive environment
to be used in the test. Periodic hydrostatic testing of the test cell is recommended to ensure pressure capabilities.
6.4 The test cell shall be designed to have the necessary inlet and outlet ports to allow the test environment to be established
in a controllable manner, monitored and sampled during the exposure period, released in a controlled manner at the completion
of the test, and if over temperature or pressure conditions may occur, adequate over pressure release and over temperature control
equipment should be utilized.
6.5 In cases where external loading fixtures are used for stressing specimens in the HP and HTHP test environment, specially
designed feed-throughs shall be used which provide for a minimum of friction force.
6.6 Test cell feed-throughs required for external stressing may be designed to balance the internal pressure in the test vessel.
G111 − 97 (2018)
6.7 Any frictional or pressure forces (or thermal expansion) acting on the specimen through the stressing fixtures must be taken
into account when determining the actual load on the specimen.
6.8 Stressing and electrode feed-throughs shall be designed so that the electrodes or stressing rods and specimens cannot be
ejected from the test cell under pressure. Furthermore, they shall provide for electrical isolation of the specimen from the test cell
unless galvanic coupling is specifically desired.
6.9 Gripping devices shall be designed such that they are in compliance with Test Method E8E8/E8M where application of load
to the specimen is required.
7. Reagents
7.1 In corrosion testing, providing a reproducible chemical environment in which to expose the corrosion test specimens is
necessary.
7.2 In cases where the test environment is established by the mixing of chemicals in the laboratory, chemicals of reagent grade
purity with known contaminant levels are recommended. Simulations of service environments can be formulated in which
laboratory corrosion tests can be conducted.
7.3 In HP/HTHP corrosion testing, a common practice is to conduct tests in environments that have been sampled and retrieved
from field or plant locations. In both cases described in 7.2 and 7.3, detailed information as to the chemical composition of the
environment should be obtained. Particular attention should be given to the levels of impurities and contaminants that may be in
the environment. Furthermore, under some conditions, these environments may be prone to changes after sampling or during
testing which can affect the corrosion test results.
7.4 In many cases, the test cells used to conduct HP tests are limited in volume and may not be designed to accommodate
replenishment of the environment. Therefore, monitoring the chemical composition of the environment during the exposure may
be necessary to identify if depletion of reactive constituents or concentration of constituents has occurred. In some cases,
replenishment or changing of the test environment may be necessary so that a valid corrosion test can be conducted.
7.5 In all cases, it is recommended that the test environment be fully documented with respect to its chemical composition.
8. Test Specimens
8.1 Preparation of Specimens:
8.1.1 The primary objective is to prepare a reproducible metallic surface with an absolute minimum of coldworking followed
by cleaning and degreasing.
8.1.2 Since test cells for HP and HTHP tests are usually of metallic construction, care must be taken to electrically isolate the
specimens from the test cell unless galvanic coupling is specifically desired in the test. In cases where the test cell is used as a
member of a galvanic couple, care must be taken to ensure that the galvanic action (anodic or cathodic) does not degrade the
integrity of the test cell.
8.2 Corrosion Specimens:
8.2.1 Prepare specimens used in HP or HTHP corrosion tests in accordance with Practices G1 and G31. Commonly, test cells
used for HP and HTHP exposure tests are restricted in volume. The available volume in the test cell often decreases with increasing
pressure rating. Therefore, it is frequently necessary to restrict the size and surface area of corrosion coupons used in HP and HTHP
corrosion tests.
8.2.2 The ratio of solution volume-to-specimen surface area is important and a minimum ratio of 30 mL/cm should be
maintained, where possible. If the ratio drops below this level, it should be shown that there will not be an unacceptably high
depletion rate of important environmental constituents, or there will not be an undesirable amount of metal ion impurities added
into the test environment during the period of exposure. In all cases, the solution volume-to-specimen surfaces area used in the
test should be stated. If the test cell, specimen holders or stressing fixtures can contribute to the conditions stated above then they
should be included in the calculation of specimen surface area.
8.3 Stressed Corrosion Specimens:
8.3.1 Both self stressed and externally stressed specimens are acceptable for testing at HP and HTHP. Methods for the
fabrication and use of appropriate stressed specimens are given in the referenced documents. These include tension, bent beam,
C-ring, and U-bend specimens in accordance with Practices G49, G39, G38, and G30, respectively. Fracture mechanics specimens
can also be accommodated.
8.3.2 For similar reasons given in 8.2, when testing multiple specimens, it is recommended that the size of the specimens be
restricted to the smallest applicable specimen provided for under the appropriate standards.
8.3.3 Due to the limited access of the specimens in HP and HTHP tests, self stressed specimens are usually more convenient
than specimens that require external stressing fixtures.
8.3.4 In cases such as direct tension and fracture mechanics tests, use of external loading frames and fixtures in conjunction with
HP and HTHP corrosion tests may be desirable. In these cases, take both the frictional (sealing) forces and pressure forces acting
on the specimens into account when determining the effect of applied stress.
G111 − 97 (2018)
8.4 Electrochemical Electrodes:
8.4.1 Prepare electrodes for
...