ASTM G_Laboratory Immersion Corrosion Testing of Metals. August 18, | Author: Description. Designation: G 31 – 72 (Reapproved ). Buy ASTM G() Standard Practice for Laboratory Immersion Corrosion Testing of Metals from SAI Global. Offering ASTM G31 corrosion testing + modified tests to fit your needs and budget . Rapid, high-quality service by experts.
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It is impractical to propose an inflexible standard laboratory corrosion testing procedure for general use, except for material qualification tests where standardization is required.
Determination of Metal Corrosion Rate by ASTM G Canadian Laboratory – LCS Laboratory Inc.
The behavior of the specimens in this galvanic couple are compared with that of insulated specimens exposed on the same holder and the galvanic effects noted. G3172 surface finish to be encountered in service may be more appropriate for some testing. This practice also emphasizes the importance of recording all pertinent data and provides a checklist for reporting test data. Please help us to share our service with your friends. The procedures for determining these values are shown in detail in Test Methods E 8.
Localized corrosion is reported separately. Oxygen saturation is a function of the partial pressure of oxygen in the gas.
It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. This cannot be evaluated by mass loss alone. Proper ultrasonic procedures are an acceptable alternate.
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ASTM G31-72_Laboratory Immersion Corrosion Testing of Metals
The phenomenon of forming a protective film is observed with many corrosion-resistant materials. Current asfm approved May 1, In many such cases, corrosion rates are established by mass gain rather than mass loss. The actual time of contact of the metal with the solution must also be taken into account. The coupling awtm corrosion coupons then yields only qualitative results, as a particular coupon reflects only the relationship between these two metals at the particular area ratio involved.
A metallographic examination may confirm the presence of stress-corrosion cracking. Warning- In aetm cases the corrosion product on the reactive metals titanium and zirconium is a hard and tightly bonded oxide that defies removal by chemical or ordinary mechanical means. For proper interpretation of the results obtained, the specific influence of certain variables must be considered. We need your help to maintenance this website.
Separate and special techniques are employed for the specific evaluation of the susceptibility g31-27 metals and alloys to stress corrosion cracking see Ref. The use of towels for drying may introduce an error through contamination of the specimens with grease or g31–72. Alternatively, the coupon may be rotated through the environment, although it is then difficult to evaluate the velocity quantitatively because of the stirring effects incurred.
This can be accomplished by analysis of the solution after corrosion has occurred. Generally, if cracking is observed on the coupon, it can be taken as positive indication of susceptibility, whereas failure to effect this phenomenon simply means that it did not occur under the duration and specific conditions of the test.
In special cases for example, for aluminum and certain copper alloysa minimum of 24 h storage in a desiccator is recommended. It atm imperative to note that this usually occurs with no significant loss in mass of the test coupon, although certain refractory metals are an exception to these observations. Care should be used to avoid the removal of sound metal.
Measurement of percent elongation is a useful index of embrittlement. These factors include oxygen concentration, temperature, rate of flow, pH value, composition, and other important characteristics of the solution. Therefore, at least duplicate specimens should normally be exposed in each test. There are a number of other special types of phenomena of which one must be aware in the design and interpretation of corrosion tests.
Your comments will receive careful consideration at a meeting of the responsible technical committee, which you may attend.
ASTM G_Laboratory Immersion Corrosion Testing of Metals – Free Download PDF
For example, a small coupon is not as prone to exhibit pitting as a large one and it is possible to miss the phenomenon altogether in the corrosion testing of certain alloys, such as the AISI Type series stainless steels in chloride contaminated environments.
Extraneous effects g31–72 be encountered if the air stream impinges on the specimens. The values given in parentheses are for information only. Location of deposits, variations in types of deposits, or variations in corrosion products are extremely important in evaluating localized corrosion, such as pitting and concentration cell attack. These factors include specimen preparation, apparatus, test conditions, methods of cleaning specimens, evaluation of results, and calculation and reporting of corrosion rates.
The mechanical property commonly used for comparison is the tensile strength. These ratios can be achieved through the use of square or circular specimens of minimum thickness. Historical Version s – view previous versions of standard. This standard does not purport to address all of the safety concerns, if any, associated with its use. Last previous edition approved in as Astj 31 — 72 Masking may also be used to achieve the desired area ratios but may cause crevice corrosion problems.
A liquid atmospheric seal is required on the test vessel to prevent further contamination. This resurfacing may cause some surface work hardening, to an extent which will be determined by the vigor sstm the surfacing operation, but is not ordinarily significant.
If clad alloys are exposed, special procedures will be required to ensure that only the cladding is exposed, unless the purpose is to test the ability of the cladding to protect cut edges in the test solution. The density in the constant K cancels out the density in the corrosion rate equation.
Therefore, short tests on such materials would indicate a high corrosion rate and be completely misleading. For example, the accumulation of cupric ions in the testing of copper alloys in intermediate strengths of sulfuric acid will accelerate the corrosion of copper alloys, as compared to the rates that would be obtained if the corrosion g31-2 were continually removed.
This can be done by chemical treatment picklingelectrolytic removal, or by grinding with a coarse abrasive paper or astj such as No. Close attention and a more sophisticated evaluation than a simple mass loss measurement are required to detect this phenomenon.
It may be desirable to test a surface representative of the material and metallurgical conditions used in practice.