A number in parentheses indicates the year of last reapproval. A superscript epsilon? This standard has been approved for use by agencies of the U. Department of Defense.
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A number in parentheses indicates the year of last reapproval. A superscript epsilon? This standard has been approved for use by agencies of the U. Department of Defense. These tests do not provide a basis for predicting resistance to forms of corrosion other than intergranular, such as general corrosion, pitting, or stress-corrosion cracking.
The inch-pound equivalents are in parentheses and may be approximate. 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. Some speci? Referenced Documents 2. Current edition approved Sept. Published September Originally approved in Last previous edition approved in as A — DOI: United States 1 A?
Purity of Reagents 3. Unless otherwise indicated, it is intended that all reagents conform to the speci? Other grades may be used, provided it is? Scope 4. Use of A Practice A as a stand-alone test may reject material that the applicable hot acid test would? Such specimens have low corrosion rates in the various hot acid tests which require from 15 to h of exposure.
These specimens are identi? Specimens having acceptable etch structures need not be subjected to the hot acid test. Specimens having suspect etch structures must be tested in the speci? Pharmacopeial Convention, Inc. Base metal has none of these conditions. Summary of Practice 5. The etched specimen is then examined using a metallurgical microscope.
The etched structure is compared with reference photographs to determine whether the material is acceptable or suspect. Suspect material is then subjected to the speci? Apparatus 7. Alternatively, the electrolyte container may be glass or other non-conducting, corrosion resisting material in lieu of a stainless steel container, and the cathode may be a? In this latter case, the? Other con? In any case, the size and shape of the specimen dictate the size and construction of the etching cell and of the power source and controls.
The overriding principle is that the etch needs to be uniform over the surface to be examined. Reagents and Materials 8. Stir until all crystals are dissolved.
Stir until dissolved. Sampling and Test Specimens 9. Additional instructions speci? Only such? If any cross-sectional dimension is less than 1 cm, then the other dimension of the cross-section should be a minimum of 1 cm.
When both dimensions of the product are less than 1 cm, use a full cross section. Not all scratches need to be removed. Procedure Gas, which is rapidly evolved at the electrodes with some entrainment of oxalic acid, is poisonous and irritating to mucous membranes.
This increases the resistance of the etching cell. When this occurs, remove the? This may be done by alternating two containers. One may be cooled in tap water while the other is used for etching. Therefore, keep the area to be etched as small as possible while at the same time meeting the requirements of desirable minimum area to be etched. In such cases, an alternate electrolyte of ammonium persulfate may be used in place of oxalic acid. See 8. If any of these conditions are found, note their presence in the report.
Steps between austenite matrix and ferrite pools. Deep interconnected ditches. Of importance only when the nitric acid test is used. Of importance only when nitric acid test is used. In cases that appear to be dual structures, more extensive examination is required to determine if there are any grains completely encircled. If an encircled grain is found, classify the steel as a ditch structure. Such sharp, deep pits should not be confused with the shallow pits shown in Figs.
Use of Etch Structure Classi? Precision and Bias NOTE 1—To differentiate between the types of pits, use a magni? The pits which now appear completely black are end grain pits. Scope The test does not provide a basis for predicting resistance to forms of corrosion 5 are entirely absent. However, any susceptibility to intergranular attack is readily detected by pronounced ditches. If these pits are sharp and so deep that they appear black Fig. The resulting mass loss is converted to a corrosion rate, which is compared to a speci?
Such specimens are acceptable without testing in the ferric sulfatesulfuric acid test. All specimens having suspect etch structures shall be tested in the ferric sulfate-sulfuric acid test. Apparatus Rapid Screening Test Preparation, etching, and the classi? The use of etch structure evaluations in connection with the ferric sulfate-sulfuric acid test is speci?
Corrosion rates obtained using the cold-? Such lower corrosion rates lead to acceptance of material that should be rejected. In the latter case Practices A would pass material that should have been subjected to the ferric sulfate-sulfuric acid test.
B Specimens having these structures shall be tested in the ferric sulfate-sulfuric acid test. It must be sized so as to? It must be designed to allow free? NOTE 5—Other equivalent means of specimen support, such as glass hooks or stirrups, may also be used. Reagents and Materials Substitutions are not permitted. Place the test? Add the acid slowly and with constant stirring to the water in the Erlenmeyer?
NOTE 7—Loss of vapor results in concentration of the acid. Preparation of Test Specimens The length of time of heating, and the method of subsequent cooling used for this sensitizing treatment together with the corresponding maximum permissible corrosion rate shall be as agreed between the material producer and purchaser.
If abrasive paper is used dry, polish slowly to avoid overheating. Do not use abrasives with grinding aids; some grinding aids contain? Residual oxide scale causes galvanic action and consequent activation in the test solution.
Dry the 7 It is important to ensure that the concentration of acid does not increase and that an adequate number of boiling chips which are resistant to attack by the test solution are present.
Sampling Welding, carburization, mechanical deformation, and the like, affect only part of a specimen. Details of the test and acceptance criteria shall be as agreed by the purchaser and producer.
Badal The test is generally performed for acceptance of materials, but not sufficient for rejection of materials. It depends on which Practice is selected, but typically ranges from to days for different tests. Historical Version s — view previous versions of standard. A recent publication on intergranular corrosion.
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