ASTM International - ASTM G78-20

Standard Guide for Crevice Corrosion Testing of Iron-Base and Nickel-Base Stainless Alloys in Seawater and Other Chloride-Containing Aqueous Environments

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Organization:	ASTM International
Publication Date:	1 November 2020
Status:	active
Page Count:	7
ICS Code (Corrosion of metals):	77.060

significance And Use:

4.1 This guide covers procedures for crevice-corrosion testing of iron-base and nickel-base stainless alloys in seawater. The guidance provided may also be applicable to crevice corrosion testing in other chloride containing natural waters and various laboratory prepared aqueous chloride environments.

4.1.1 While this guide focuses on testing of iron-base and nickel-base stainless alloys, the procedures and evaluations methods described herein have been successfully applied to characterize the crevice corrosion performance of other alloy systems (see, for example, Aylor et al.3).

Note 1: In the case of copper alloys, the occurrence of crevice-related corrosion associated with different corrosion mechanisms takes place immediately adjacent to the crevice former rather than within the occlusion.

4.2 This guide describes the use of a variety of crevice formers including the nonmetallic, segmented washer design referred to as the multiple crevice assembly (MCA) as described in 9.2.2.

4.3 In-service performance data provide the most reliable determination of whether a material would be satisfactory for a particular end use. Translation of laboratory data from a single test program to predict service performance under a variety of conditions should be avoided. Terms, such as immunity, superior resistance, etc., provide only a general and relatively qualitative description of an alloy's corrosion performance. The limitations of such terms in describing resistance to crevice corrosion should be recognized.

4.4 While the guidance provided is generally for the purpose of evaluating sheet and plate materials, it is also applicable for crevice-corrosion testing of other product forms, such as tubing and bars.

4.5 The presence or absence of crevice corrosion under one set of conditions is no guarantee that it will or will not occur under other conditions. Because of the many interrelated metallurgical, environmental, and geometric factors known to affect crevice corrosion, results from any given test may or may not be indicative of actual performance in service applications where the conditions may be different from those of the test.

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scope:

1.1 This guide covers information for conducting crevice-corrosion tests and identifies factors that may affect results and influence conclusions.

1.2 These procedures can be used to identify conditions most likely to result in crevice corrosion and provide a basis for assessing the relative resistance of various alloys to crevice corrosion under certain specified conditions.

1.3 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.

1.4 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. For a specific warning statement, see 7.1.

1.5 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.