ASTM G111-21a

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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
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Designation: G111 − 21 G111 − 21a
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.
1.2 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.
1.3 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.
1.4 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.
1.5 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.
1.6 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:
E8/E8M Test Methods for Tension Testing of Metallic Materials
G1 Practice for Preparing, Cleaning, and Evaluating Corrosion Test Specimens
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 Sept. 15, 2021Nov. 1, 2021. Published October 2021December 2021. Originally approved in 1992. Last previous edition approved in 20182021
as G111 – 97 (2018).G111 – 21. DOI: 10.1520/G0111-21.10.1520/G0111-21A.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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G3G4 Practice for Conventions Applicable to Electrochemical Measurements in Corrosion TestingGuide for Conducting
Corrosion Tests in Field Applications
G5 Reference Test Method for Making Potentiodynamic Anodic Polarization Measurements
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
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
G129 Practice for Slow Strain Rate Testing to Evaluate the Susceptibility of Metallic Materials to Environmentally Assisted
Cracking
G170 Guide for Evaluating and Qualifying Oilfield and Refinery Corrosion Inhibitors in the Laboratory
G184 Practice for Evaluating and Qualifying Oil Field and Refinery Corrosion Inhibitors Using Rotating Cage
G185 Practice for Evaluating and Qualifying Oil Field and Refinery Corrosion Inhibitors Using the Rotating Cylinder Electrode
G193 Terminology and Acronyms Relating to Corrosion
G208 Practice for Evaluating and Qualifying Oilfield and Refinery Corrosion Inhibitors Using Jet Impingement Apparatus
3. Terminology
3.1 Definitions—The definitions of terms given in Terminology G193 shall be considered as applying to this guide.
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3.2 Definitions of Terms Specific to This Standard:
3.2.1 high pressure—temperature and high pressure, HTHP, n—a pressure above ambient atmospheric pressure that cannot be
contained in normal laboratory glassware. Typically, this is greater than 0.07 MPa (10 psig).for the purpose of this guide, any
combination of pressure and temperature that requires the use of an autoclave.
3.2.2 high temperature—effectively non-reactive, adj—temperatures above ambient laboratory temperature where sustained
heating of the environment is required.free of significant mass loss or localized corrosion, stress corrosion cracking (SCC), or other
embrittlement phenomena in the test environment; not contaminate the test environment with corrosion or other reaction products;
and not significantly consume, absorb, or adsorb reactive chemical species from the test environment.
3.3 Abbreviations and Acronyms:
3.3.1 AI—artificial intelligence
3.3.2 ALARP—as low as reasonably practicable
3.3.3 CUE—corrosion under excursions
3.3.4 HV—high velocity
3.3.5 ML—machine learning
3.3.6 PVT—pressure volume temperature
3.3.7 RT—radiography testing (X-ray)
3.3.8 SCC—stressed-corrosion cracking
3.3.9 SME—subject matter expert
3.3.10 UT—ultrasonic testing
4. Summary of Guide
4.1 This guide describes the use of corrosion coupons, stressed SCC stress corrosion cracking specimens, and electrochemical
electrodes in HP and HTHP environments. It also includes guidelines for the use of high pressure high-pressure test cells with these
specimens to conductobtain reproducible, accurate corrosion test data.
4.2 Typically, HP and HTHP 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 mustshall be able to resist corrosion and environmental cracking
cracking (mechanical and environmental) in the test environment while containing the pressurized, heated environment.
Furthermore, the test specimens in the HP or HTHP 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 Autoclave 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.and
non-metallic materials under simulated HP and HTHP service conditions. Examples of service environments where in which HP
and HTHP corrosion tests have been utilizedused 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 environment 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 pressure, among other parameters, usually drive the composition and properties of the aqueous phase and, hence,
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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 low-pressure
glassware experiments cannot be followed due to the limitations of access, volume, and visibility arising from the construction of
high pressure high-pressure test cells. This guide refers to existing corrosion standards and practices, as applicable, and then goes
further in areas where in which 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.
6.1 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.Test Cell:
6.1.1 Shall be constructed to applicable standards and codes so that it will have an adequate pressure rating to handle the test
pressure safely.
6.1.2 Shall be made of materials that are corrosion resistant and effectively non-reactive with the test environment.
6.1.3 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 retaining capabilities.
6.1.4 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 used.
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.
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.
6.2 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.Test Cell Feedthroughs:
6.2.1 Should be designed to minimize frictional forces when external loading fixtures are used for stressing specimens.
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6.2.2 May be designed to balance the internal pressure in the test vessel with the external stressing assembly.
6.2.3 Shall be designed so that the electrodes or stressing rods and specimens cannot be ejected from the test cell under pressure.
6.2.4 Shall provide the electrical isolation of the specimen from the test cell unless galvanic coupling is specifically desired.
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6.3 Gripping devices shall be designed such that they are in compliance with Test Methods E8/E8M where application of load to
the specimen is required.Specimen Under Applied Load:
6.3.1 Any frictional or pressure forces (or thermal expansion) acting on the specimen through the stressing fixtures should be taken
into account when determining the actual load on the specimen.
6.3.2 Gripping devices should be designed such that they are in compliance with Test Methods E8/E8M where application of load
to the specimen is required.
6.4 Agitation:
6.4.1 Agitation can be achieved by using a magnetic stir bar/plate, mechanically agitating the autoclave, for example, rollers
within an oven recirculating the fluid through a pump, or using magnetic/mechanical feedthrough stirrers designed for this purpose.
Care should be taken to ensure that components of the pump or stirrer are inert to the test environment.
NOTE 1—The potential for oxygen contamination and pressure loss increase with the use of pumps and additional autoclave ports.
6.4.2 Descriptions of test methods and equipment designs for testing under turbulent flow conditions, defined as a function of wall
shear stress or mass transfer coefficient, can be found collectively in Guide G170, Practice G184 (rotating cage autoclaves),
Practice G185 (rotating cylinder electrodes), and Practice G208 (jet impingement).
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
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 Detailed 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.
7.4 In all cases, it is recommended that the test environment be fully documented with respect to its chemical composition.
8. Sampling and Test Specimens
8.1 Sampling Selection Process—Refer to G4, Standard Guide for Conducting Corrosion Tests in Field Applications.
8.2 Preparation of Specimens:
8.2.1 The Frequently, the primary objective is to prepare a reproducible metallic surface with an absolute minimum of
coldworking cold working followed by cleaning and degreasing. However, there are cases where the as-received surface is the
desired test surface, or where the effect of cold working is to be studied.
8.2.2 Since test cells for HP and HTHP tests are usually of metallic construction, care must be taken to electrically isolate the
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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.
8.3 Corrosion Specimens:
8.3.1 Prepare specimens used in HP or HTHP corrosion tests in accordance with Practice G1 and Guide 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.tests to attain a given volume to area ratio.
8.3.2 The ratio A minimum ratio, R,of solution volume-to-specimen surface area is important and a minimum ratio of 30 mL/cm
is often set for the volume of corrosive liquid to the surface area of the metal that can be corroded, for example, 200 L ⁄m should
2 2 2
beto 400 L ⁄m maintained, whereor 20 mL ⁄cm possible. Ifto 40 mL ⁄cm (Guide G31, Test Method G34, and Practice G185the
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 origin of this
concept is to minimize the buildup of corrosion products, which could subsequently impact solution pH, scaling tendencies, general
corrosion rate, pit initiation, and pitting rates. Additionally, R can impact the rate at which reactants are depleted and potentially
undesirable changes to the test environment during occur. Consequently, an acceptable value for Rthe period of exposure. In all
cases, the solution volume-to-specimen will depend on the highest expected corrosion rate and the test duration. Another factor,
not accounted for by R,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. arises from the
possibility that certain chemicals, for example, components in a corrosion inhibitor, may adsorb (competitively) on metal surfaces
other than the test specimen. Hence, in designing a test, one might also consider how the ratio of total immersed metal surface area
to liquid volume compares with that in the field.
8.4 Stressed Corrosion Specimens:
8.4.1 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 theSection 2referenced documents. . These include tension, bent beam,
C-ring, and U-bend specimens in accordance with Practices G129, G49, G39, G38, and G30, respectively. Fracture mechanics
specimens can also be accommodated.
8.4.2 For similar reasons given in 8.28.3, 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.
8.4.3 Due toBecause of the limited access of the specimens in HP and HTHP tests, self stressed self-stressed specimens are usually
more convenient than specimens that require external stressing fixtures.
8.4.4 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.
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8.5 Electrochemical Electrodes:
8.5.1 Prepare electrodes for use in HP and HTHP corrosion studies as described in Practice G3, Reference Test Method G5, Test
Method G59, and Practice G106.
8.5.2 Cylindrical electrode specimens where in which only the lower portion of the electrode is exposed to the liquid phase of test
environment, and where the electrical connections are made externally to the test cell are a convenient geometry. Care mustshall
be taken to electrically isolate the electrodes electrically from the test cell. Other electrode geometries and designs may be used
that facilitate feed-throughfeedthrough and electrical isolation.
8.5.3 A critical portion of the HP or HTHP electrochemical system is the design and construction of the reference electrode. It is
common to use external reference cells that use stable reference systems such as Ag/AgCl or otheranother stable electrochemical
reference system that can be enclosed in a separate pressure containing compartment. This cell is then connected to the test cell
by means of a salt bridge and is pressure balanced with the test cell to minimize ingress of contaminants into either the test cell
or the reference electrode. Alternatively, an inert or corroding metal electrode can be used as a pseudo-reference non-standard
reference electrode in some cases. Examples of such pseudo-reference non-standard reference electrodes include platinum,
graphite, or other metal with known stable corrosion potential. However, one problem that can occur with this technique is a drift
in reference potential with time. Care should be taken when employingusing such methods. These pseudo-reference non-standard
reference electrodes can effectively give a measure of relative potential even if the absolute potential is not known.
9. Test Environment
9.1 Choose the test environment to either simulate give the most accurate possible representation of the service environment
possible under (within the constraints of the equipment availableavailable) or provide for a simple screening environment. In the
case of service environment simulation, accurate monitoring for depletion and concentration of chemical species in the test cell
is required so that the environment can be controlled within a specified range of composition. In the case of simple screening
environments, allowance for greater latitude in the variance of the test environment from service conditions is acceptable. In this
case, simple solutions are commonly utilized and chemical monitoring is not conducted.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.
9.1.1 In the case of service environment simulation, monitoring concentrations of chemical species in the test cell may be needed
to check that the environment is within a specified range of compositions (see 9.6). In some cases, replenishment of the test
environment may be necessary. The need for replenishment may be influenced by factors such as test duration and the stability/life
of any additives relative to the test duration.
9.1.2 In the case of simple screening environments, allowance for greater latitude in the variance of the test environment from
service conditions is acceptable, and chemical monitoring may not be required.
9.2 Test Temperature:
9.2.1 Care should be taken to control the temperature as closely as possible because small temperature changes can significantly
affect process rates. The test temperature should be controlled to within 61.0 % 63 °C of the specified temperature or 62.5 °C,
whichever is greater, unless otherwise specified.targeted temperature. Many temperature controllers are susceptible to overshooting
the set point upon initial temp-up. The time required to reach the test temperature should be recorded and kept constant throughout
the test matrix. If the set point is exceeded, the magnitude and duration of the deviation should be documented.
9.2.2 Temperature of the liquid phase can be measured in one location if the specimens are totally contained therein. therein, and
the solution is sufficiently agitated. However, for large test cells substantial cells, temperature gradients higher than specified in
9.2.1 can exist and,and care should be taken to monitor the temperature close to the specimens using thermocouples contained in
corrosion resistant sheaths. In this case, the thermocouples should be positioned to limit their impact on the fluid flow over adjacent
coupons.
9.2.3 In tests where in which the specimens are exposed to the gaseous or vapor phase, care mustshall be taken to obtain direct
measurements of specimen temperature. When the test vessel is heated externally, the vessel temperature may greatly exceed the
specimen temperature. Internally heating the specimen may be possible in the gaseous environment. Such a procedure is
particularly useful when conditions of heat transfer are being simulated.
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9.3 Pressure:
9.3.1 The pressure shall be monitored and recorded as required by internal/external safety protocols, and the project’s scope of
work using either a pressure gauge or pressure transducer.
9.3.2 Pressure sensors accuracy and range should be selected to measure changes precisely at least 1 % of the target pressures.
Sensors should be recalibrated at regular intervals because drift can occur over time.
9.3.3 An acceptability criterion for the departure of pressure from target values and corrective actions should be defined depending
on the corrosion system. Departures may occur during the test because of minor leaks or changes in the environment (for example,
gas consumption, hydrogen generation).
9.3.4 The pressure should be monitored continuously or periodically during the exposure period using either a pressure gage or
pressure transducer. Care shall be taken to properly select materials of construction properly for these measurement devices if
exposed directly to the test environment. Methods to minimize corrosion of pressure monitoring equipment are to provide for an
isolation valve between the monitoring equipment or to utilize use a diaphragm seal that transmits the pressure from the test cell
to the monitoring equipment by means of a chemically inert media.
9.4 Liquid Constituent(s):
9.4.1 In single phase liquid environments, the solution is often static with only convection to provide agitation. However, it can
The volume of the liquid phase(s) should be recorded along with the autoclave’s effective volume, that is, the volume of the
autoclave minus the test fixtures and specimens. It is common for the liquid phase(s) to acc
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