ASTM G185-06(2020)e1

Standard Practice for Evaluating and Qualifying Oil Field and Refinery Corrosion Inhibitors Using the Rotating Cylinder Electrode

SIGNIFICANCE AND USE
5.1 Selection of corrosion inhibitor for oil field and refinery applications involves qualification of corrosion inhibitors in the laboratory (see Guide G170). Field conditions should be simulated in the laboratory in a fast and cost-effective manner (1).3  
5.2 Oil field corrosion inhibitors should provide protection over a range of flow conditions from stagnant to that found during typical production conditions. Not all inhibitors are equally effective over this range of conditions so that is important for a proper evaluation of inhibitors to test the inhibitors using a range of flow conditions.  
5.3 The RCE is a compact and relatively inexpensive approach to obtaining varying hydrodynamic conditions in a laboratory apparatus. It allows electrochemical methods of estimating corrosion rates on the specimen and produces a uniform hydrodynamic state across the metal test surface. (2-21)  
5.4 In this practice, a general procedure is presented to obtain reproducible results using RCE to simulate the effects of different types of coupon materials, inhibitor concentrations, oil, gas and brine compositions, temperature, pressure, and flow. Oil field fluids may often contain sand. This practice does not cover erosive effects that occur when sand is present.
SCOPE
1.1 This practice covers a generally accepted procedure to use the rotating cylinder electrode (RCE) for evaluating corrosion inhibitors for oil field and refinery applications in defined flow conditions.  
1.2 The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for information only and are not considered standard.  
1.3 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.  
1.4 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-Oct-2020
• ICS: 75.200 - Petroleum products and natural gas handling equipment
• Technical Committee: G01 - Corrosion of Metals
• Drafting Committee: G01.05 - Laboratory Corrosion Tests

Relations

• Refers: ASTM G3-14(2019) - Standard Practice for Conventions Applicable to Electrochemical Measurements in Corrosion Testing
• Effective Date: 01-May-2019
• Refers: ASTM G16-13(2019) - Standard Guide for Applying Statistics to Analysis of Corrosion Data
• Effective Date: 15-Feb-2019
• Refers: ASTM G96-90(2018) - Standard Guide for Online Monitoring of Corrosion in Plant Equipment (Electrical and Electrochemical Methods)
• Effective Date: 01-May-2018
• Refers: ASTM D4410-16 - Terminology for Fluvial Sediment
• Effective Date: 01-Jan-2016
• Refers: ASTM G3-14 - Standard Practice for Conventions Applicable to Electrochemical Measurements in Corrosion Testing
• Effective Date: 15-Dec-2014
• Refers: ASTM G5-14 - Standard Reference Test Method for Making Potentiodynamic Anodic Polarization Measurements
• Effective Date: 01-Nov-2014
• Refers: ASTM G3-13 - Standard Practice for Conventions Applicable to Electrochemical Measurements in Corrosion Testing
• Effective Date: 01-Dec-2013
• Refers: ASTM G16-13 - Standard Guide for Applying Statistics to Analysis of Corrosion Data
• Effective Date: 01-Dec-2013
• Refers: ASTM G96-90(2013) - Standard Guide for Online Monitoring of Corrosion in Plant Equipment (Electrical and Electrochemical Methods)
• Effective Date: 01-Aug-2013
• Refers: ASTM G111-97(2013) - Standard Guide for Corrosion Tests in High Temperature or High Pressure Environment, or Both
• Effective Date: 01-May-2013
• Refers: ASTM G46-94(2013) - Standard Guide for Examination and Evaluation of Pitting Corrosion
• Effective Date: 01-May-2013
• Refers: ASTM G5-13 - Standard Reference Test Method for Making Potentiodynamic Anodic Polarization Measurements
• Effective Date: 01-Feb-2013
• Refers: ASTM G5-13e2 - Standard Reference Test Method for Making Potentiodynamic Anodic Polarization Measurements
• Effective Date: 01-Feb-2013
• Refers: ASTM G5-13e1 - Standard Reference Test Method for Making Potentiodynamic Anodic Polarization Measurements
• Effective Date: 01-Feb-2013
• Refers: ASTM G5-12 - Standard Reference Test Method for Making Potentiostatic and Potentiodynamic Anodic Polarization Measurements
• Effective Date: 15-Nov-2012

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.
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Designation:G185 −06 (Reapproved 2020)
Standard Practice for
Evaluating and Qualifying Oil Field and Refinery Corrosion
Inhibitors Using the Rotating Cylinder Electrode
This standard is issued under the fixed designation G185; 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.
ε NOTE—Replaced Terminology G15 with Terminology G193, and other editorial changes made throughout in Dec. 2020.
1. Scope G1 Practice for Preparing, Cleaning, and Evaluating Corro-
sion Test Specimens
1.1 This practice covers a generally accepted procedure to
G3 Practice for Conventions Applicable to Electrochemical
use the rotating cylinder electrode (RCE) for evaluating
Measurements in Corrosion Testing
corrosion inhibitors for oil field and refinery applications in
G5 Reference Test Method for Making Potentiodynamic
defined flow conditions.
Anodic Polarization Measurements
1.2 The values stated in SI units are to be regarded as
G16 Guide for Applying Statistics to Analysis of Corrosion
standard. The values given in parentheses after SI units are
Data
provided for information only and are not considered standard.
G31 Guide for Laboratory Immersion Corrosion Testing of
1.3 This standard does not purport to address all of the Metals
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-
G59 Test Method for Conducting Potentiodynamic Polariza-
mine the applicability of regulatory limitations prior to use. tion Resistance Measurements
1.4 This international standard was developed in accor-
G96 Guide for Online Monitoring of Corrosion in Plant
dance with internationally recognized principles on standard- Equipment (Electrical and Electrochemical Methods)
ization established in the Decision on Principles for the
G102 Practice for Calculation of Corrosion Rates and Re-
Development of International Standards, Guides and Recom-
lated Information from Electrochemical Measurements
mendations issued by the World Trade Organization Technical G106 Practice for Verification of Algorithm and Equipment
Barriers to Trade (TBT) Committee.
for Electrochemical Impedance Measurements
G111 Guide for Corrosion Tests in High Temperature or
2. Referenced Documents High Pressure Environment, or Both
2 G170 Guide for Evaluating and Qualifying Oilfield and
2.1 ASTM Standards:
Refinery Corrosion Inhibitors in the Laboratory
D1141 Practice for the Preparation of Substitute Ocean
G193 Terminology and Acronyms Relating to Corrosion
Water
D4410 Terminology for Fluvial Sediment
3. Terminology
3.1 The terminology used throughout shall be in accordance
with Terminologies G193 and D4410 and Guide G170.
This practice 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.
4. Summary of Practice
Current edition approved Nov. 1, 2020. Published December 2020. Originally
4.1 This practice provides a method of evaluating corrosion
approved in 2006. Last previous edition approved in 2016 as G185 – 06 (2016).
DOI: 10.1520/G0185-06R20E01.
inhibitor efficiency in a RCE apparatus. The method uses a
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
well-defined rotating specimen set up and mass loss or elec-
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
trochemical measurements to determine corrosion rates in a
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. laboratory apparatus. Measurements are made at a number of
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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G185−06 (2020)
rotating rates to evaluate the inhibitor performance under 6.4 A saturated calomel electrode (SCE) with a controlled
increasingly severe hydrodynamic conditions. rate of leakage or a saturated calomel electrode utilizing a
semipermeable membrane or porous plug tip or silver/silver
5. Significance and Use
chloride or any other suitable electrode should be used as
5.1 Selection of corrosion inhibitor for oil field and refinery reference electrode. The potential of the reference electrode
applicationsinvolvesqualificationofcorrosioninhibitorsinthe should be checked at periodic intervals to ensure the accuracy
laboratory (see Guide G170). Field conditions should be of the electrode. For experiments at higher-temperature, a
simulated in the laboratory in a fast and cost-effective manner higher-pressure,referenceelectrodearrangementthatcanwith-
(1). stand higher temperature and pressure should be used (22).
This may require special care.
5.2 Oil field corrosion inhibitors should provide protection
over a range of flow conditions from stagnant to that found 6.5 Fig. 2 shows a typical rotating electrode unit.Arotating
shaft can be modified by drilling a hole in the shaft into which
during typical production conditions. Not all inhibitors are
equally effective over this range of conditions so that is a polytetrafluoroethylene (PTFE) insulator is inserted. Inside
the PTFE insulator, a metal rod should be introduced (Fig. 2).
important for a proper evaluation of inhibitors to test the
inhibitors using a range of flow conditions. One end of the metal rod is threaded so that the cylindrical
electrode can be attached. The other end of the rod is attached
5.3 The RCE is a compact and relatively inexpensive
directly to the rotating unit, through which the electrical
approach to obtaining varying hydrodynamic conditions in a
connection is made.
laboratory apparatus. It allows electrochemical methods of
6.6 After attaching the specimen to the shaft, the system
estimating corrosion rates on the specimen and produces a
should be checked for eccentricity and wobble. This can be
uniform hydrodynamic state across the metal test surface.
accomplished by installing a dial micrometer so as to monitor
(2-21)
the location of the top of the rotating cylinder and rotating the
5.4 In this practice, a general procedure is presented to
shaft slowly through one complete turn. The micrometer
obtainreproducibleresultsusingRCEtosimulatetheeffectsof
should then be moved to monitor the center of the specimen,
different types of coupon materials, inhibitor concentrations,
and the process repeated. Finally the micrometer should be
oil, gas and brine compositions, temperature, pressure, and
moved to the bottom of the specimen and the process repeated.
flow.Oilfieldfluidsmayoftencontainsand.Thispracticedoes
The assembly should also be rotated at its maximum rotation
not cover erosive effects that occur when sand is present.
rate and the specimen wobble checked again using, for
example, a laser indicator or vibration monitor.
6. Apparatus
6.7 Appropriate cylinder specimen (such as, carbon steel) is
6.1 Fig. 1 shows a schematic diagram of the RCE system.
machined and snugly fitted into the PTFE or any other suitable
The RCE apparatus consists of a rotating unit driven by a
specimen holder (Fig. 2). The presence of gap between
motorthatisattachedtoasampleholder.Asystemwitharange
specimen and holder will create crevice corrosion as well as
of rotational speeds from 100 rpm to 10 000 rpm with an
change the flow pattern. If necessary, apply a very small
accuracyof 62rpmistypical.Itisessentialtobeabletorotate
amount of epoxy to fit the specimen into the holder. Tightly
the electrode at both low and high speeds and to be able to
attach or screw an end-cap so that only the outer cylindrical
measure the speed and maintain it at a constant. The accuracy
area of known length is exposed to the solution. The specimen
oftherotationrateshouldbechecked.Atthesideofthesample
holder is then attached to the rotating unit. Specimen, holder,
holder where it is outside the cell, electrical connections to the
and end-cap should all have the same diameter.
electrodes are made by a brush contact. It is important for the
connection to be as noise free as possible.
6.8 The rotating unit is attached into the experimental
vessel, ensuring that there is no leakage through the rotating
6.2 The cylinder geometry is usually defined in terms of the
shaft and the holder and that the rotating shaft is vertically
length-to-diameter ratio. Both low and high ratios are used,
positioned. Even a very slight inclination could drastically
with ratios varying between 0.3 and 3.0. The rotating cylinder
change the flow pattern.
can also be used as a mass loss coupon when the mass loss is
sufficiently large to be accurately measured using a conven-
6.9 A versatile and convenient apparatus, consisting of a
tional balance (with accuracy of 0.1 mg).
kettle or flask (Fig. 1) of suitable size (usually 500 mL to
5000 mL),inletandoutletportsfordeaeration,thermowelland
6.3 The RCE geometry may have an inner cylinder and an
temperature-regulating device, a heating device (mantle, hot
outer cylinder. The geometry is usually defined in terms of the
plate, or bath), and a specimen support system, should be used.
radius of the inner cylinder and the radius of the outer cylinder.
The volume (of the solution) to surface area (of the specimen)
When the outer diameter is several times the diameter of the
ratio has some effect on the corrosion rate and hence inhibitor
innerelectrodethehydrodynamicsareessentiallycontrolledby
efficiencies. A larger volume/surface area (minimum 40 mL/
the diameter of the inner rotating cylinder (2). The outer
cm ) should be preferred.
cylinder may act as counter electrode. An RCE with only an
inner cylinder may also be used.
6.10 In some cases a wide-mouth jar with a suitable closure
can be used, but open-beaker tests should not be used because
of evaporation and contamination. Do not conduct the open-
The boldface numbers in parentheses refer to the list of references at the end of
this standard. beaker test when H S (hydrogen sulfide) is used. In more
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G185−06 (2020)
A. Reference Electrode
B. Inlet
C. Outlet
D. Luggin Capillary
E. Counter Electrode
F. Rotating Cylinder
G. Temperature Probe
H. pH Electrode
I. Rotating Cylinder Electrode or Coupon
FIG. 1Schematic of a RCE System (18)
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G185−06 (2020)
A. Outside View
B. Cross-Sectional View
FIG. 2Schematic Representation of a RCE with its Components (adapted from Ref 18)
complex tests, provisions might be needed for continuous flow Standardlaboratoryglasswareshouldbeusedforweighingand
or replenishment of the corrosive liquid, while simultaneously measuring reagent volumes.
maintaining a controlled atmosphere.
7.2 The specimen shall be made of the material (such as,
6.11 For experiments above atmospheric pressure, a high-
carbon steel) for which the inhibitor is being evaluated. The
temperature, high-pressure rotating cylinder electrode (HTH-
specimen should have same metallographic structure as that
PRCE) system with an electrically isolated electrode system,
used in the service components. The specimens should be
an electrically isolated motor for rotating the electrode, and a
ground to a specified surface finish (such as, 150 grit). The
vessel that can withstand high pressure without leakage should
grinding should produce a reproducible surface finish, with no
be used.
rust deposits, pits, or deep scratches. All sharp edges on the
specimen should be ground. All loose dirt particles should be
6.12 A design of the vessel that can be used in elevated
removed.
pressure conditions (23, 24) include a standard autoclave (Fig.
3) modified by lining on the inside with PTFE.The stirring rod
7.3 Thespecimensarerinsedwithdistilledwater,degreased
can be modified by drilling a hole into that a PTFE insulator is
by immersing in acetone (or any suitable alcohol), ultrasoni-
inserted. Inside the PTFE insulator, a metal rod is introduced.
cally cleaned for 1 min, and dried. The surface of the
Three O-rings are used to secure and to prevent leakage. One
specimens should not be touched with bare hands. The speci-
end of the metal rod is threaded so that cylindrical (Fig. 3)
mens are weighed to the nearest 0.1 mg (for mass loss
electrode can be attached. The other end of the rod, projecting
measurements), the dimensions are measured to the nearest 0.1
slightly above the motor unit, is attached directly the rotating
mm, and the surface area is calculated.
unit, through which the electrical connection is made. The rod
7.4 Freshly prepared specimens are installed in the RCE
is rotated by a motor connected to the rod using a belt. The
holder. If the test is not commenced within 4 h, the prepared
counter and reference electrodes are inserted inside the auto-
coupons shall be stored in a desiccator to avoid pre-rusting.
clave.
6.13 The suggested components can be modified,
8. Test Solutions
simplified, or made more sophisticated to fit the needs of a
8.1 All solutions (oil and aqueous) should be obtained from
particular investigation.
the field for which the inhibitor is being evaluated. These are
7. Materials
known as live solutions. It is important that live solutions do
7.1 Methods for preparing specimens for tests and for not already contain corrosion inhibitor. In the absence of live
removing specimens after the test are described in Practice G1. solutions, synthetic solutions should be used, the composition
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G185−06 (2020)
1. Electrical Contact Unit
2. Techometer (Rotation Speed Display)
3. Rotation Controller
4. Electrochemical Instruments
5. Working Electrode
6. Reference Electrode
7. Water Cooler Coil
8. Gas Inlet
9. Thermocouple
10. Gas Outlet
11. Counter Electrode
12. Autoclave Body
13. Solution
14. PTFE Liner
FIG. 3Schematic Diagram of HTHPRCE System (20,21)
can be obtained by mixing H
of which should be based on field water analysis. The compo- S and CO streams from the
2 2
sition of the solution should be determined and reported. standard laboratory gas supply. Nitrogen or other inert gases
Alternatively, standard brine (such as per Practice D1141) can be used as a diluent to obtain the required ratios of the
should be employed. The solutions should be prepared using corrosive gases. Alternatively, gas mixtures
...