ASTM G97-18(2022)

SIGNIFICANCE AND USE 5.1 This test is a guide for evaluating magnesium anodes. The degree of correlation between this test and service performance has not been fully determined. 5.2 Test specimens from the same casting may not be identical because of inhomogeneities in the casting. A method of ensuring that identical test specimens are being evaluated is to retest a test specimen. The surface of the test specimen should be smoothed by machining before retesting. The new diameter should be measured and the test current adjusted so that the retest current density is 0.039 mA/cm2 (0.25 mA/in.2). 5.3 The values of potential and Ah per unit mass consumed as measured by this test method, may not agree with those found in field applications. It is unlikely that field results of Ah per unit mass consumed would ever be greater than those measured in this test. However, actual test comparisons are not sufficient to allow precise correlation of laboratory and field results. SCOPE 1.1 This test method covers a laboratory procedure that measures the two fundamental performance properties of magnesium sacrificial anode test specimens operating in a saturated calcium sulfate, saturated magnesium hydroxide environment. The two fundamental properties are electrode (oxidation) potential and ampere hours (Ah) obtained per unit mass of specimen consumed. Magnesium anodes installed underground are usually surrounded by a backfill material that typically consists of 75 % gypsum (CaSO4·2H2O), 20 % bentonite clay, and 5 % sodium sulfate (Na2SO4). The calcium sulfate, magnesium hydroxide test electrolyte simulates the long term environment around an anode installed in the gypsum-bentonite-sodium sulfate backfill. 1.2 This test method is intended to be used for quality assurance by anode manufacturers or anode users. However, long term field performance properties may not be identical to property measurements obtained using this laboratory test. Note 1: Refer to Terminology G193 for terms used in this test method. 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 specific precautions, See Section 8 and Paragraph 9.1.1. 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.