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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Asrm factors include specimen preparation, apparatus, test conditions, methods of cleaning specimens, evaluation of results, and calculation and reporting of corrosion rates.
Care should be used to avoid the removal of sound metal. With a thickness of approximately 3 mm 0. This can be done by chemical treatment picklingelectrolytic removal, or by grinding with a coarse abrasive paper or cloth such as No. The choice of a specific treatment must be considered on the basis of the alloy to be tested and the reasons for testing.
This practice also emphasizes the importance of recording all pertinent data and provides a checklist for reporting test data. Current edition approved May 1, The degree of lateral spreading of astmm may also be noted. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the risk of infringement of such rights, are entirely their own responsibility.
These factors include specimen preparation, apparatus, test conditions, methods of cleaning specimens, evaluation of results, and calculation and reporting of corrosion rates. The phenomenon of forming a protective film is observed with many corrosion-resistant materials.
Your comments are invited either for revision of this standard or for additional standards and should be addressed to ASTM International Headquarters. Historical Version s – view previous versions of standard. The behavior of the specimens in this galvanic couple are compared with asgm of insulated specimens exposed on the same holder and the galvanic effects noted. One purpose for this guide is to promote better correlation of results in the future and the reduction of conflicting reports through a v31-72 detailed recording of meaningful factors and conditions.
A large surface-to-mass ratio and a small ratio of edge area to total area are desirable. A distinction should be made between those occurring underneath the supporting devices concentration cells and those on the surfaces that were freely exposed to the test solution see Guide G Last previous edition approved in as G 31 — 72 It is impractical to propose an inflexible standard laboratory corrosion testing procedure for general use, except for material qualification tests where standardization is obviously required.
The mechanical property commonly used for comparison is the tensile strength. Any necessary distortion of the test conditions must be considered when interpreting the results. Originally approved in Special coupons for example, sections of welded tubing may be employed for specific purposes. Corrosion testing by its very nature precludes complete standardization.
NOTE 1—The flask can be used as a versatile and convenient apparatus to conduct simple immersion tests.
ASTM G31-72_Laboratory Immersion Corrosion Testing of Metals
Warning—In many 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. Methods for chemical cleaning after xstm of specific metals and alloys are described in Practice G 1.
For example, lead exposed to sulfuric acid corrodes at an extremely high rate at first, while building a protective film; then the rates decrease considerably so that further corrosion is negligible. We need your help! Using the above units for T, A, W, and D, the corrosion rate can be calculated in a variety of units with the following appropriate value of K: For relatively soft metals such as aluminum, magnesium, and copperscrubbing with abrasive powder is not always needed and can mar the surface of the specimen.
This cannot be evaluated by mass loss alone. Molarity and normality are also helpful in defining the concentration of chemicals in some test solutions.
ASTM G31 – 72() Standard Practice for Laboratory Immersion Corrosion Testing of Metals
This practice also emphasizes the asfm of recording all pertinent data and provides a checklist for reporting test data. A commercial surface may sometimes yield the most significant results. Please copy and paste this embed script to where you want to embed Embed Script.
Oxygen saturation is a function of the partial pressure of oxygen in the gas. This cracking occurs under conditions of applied or residual tensile stress, and it may or may not be visible to the unaided eye or upon casual inspection.
Occasional exceptions, in which a large difference is observed, can occur under conditions of borderline passivity of metals or alloys that depend on a passive film for their resistance to corrosion. Most tests related to process equipment should be run with the natural atmosphere inherent in the process, such as the vapors of the boiling liquid.
If clad alloy specimens are to be used, special attention must be given to ensure that excessive metal is not removed. Scrubbing with a bristle brush and mild abrasive is the most popular of these methods. Therefore, at least duplicate specimens should normally be exposed in each test. Constant K in Corrosion Rate Equation 3. ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentioned in this standard.
The surface finish to be encountered in service may be more appropriate for some testing. It should be appreciated that pitting is a statistical phenomenon and that g31–72 incidence of pitting may be directly related to the area of metal exposed. Separate and special techniques are employed for the specific evaluation of the susceptibility of metals and alloys to stress corrosion atm see Ref. There are a number of other special types of phenomena of which one must be aware in the design and interpretation of corrosion tests.
Methods of Cleaning Specimens after Test 9. 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. If this is a factor to be considered in a specific test, the solution should be completely aerated or deaerated in accordance with 8. For example, the accumulation of cupric ions in the testing g31-7 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 products were continually removed.
A metallographic examination may confirm the presence of stress-corrosion cracking. The reporting of nonuniform corrosion is discussed below. This guide also emphasizes the importance of recording all pertinent data and provides a checklist for reporting test data.