General

This standard test method describes a laboratory procedure for determining the potential and current capacity characteristics of aluminum alloy anodes used for CP. It provides a means for screening various heats or lots of anodes to determine performance consistency on a regular basis from lot to lot. Items such as sampling frequency and performance criteria (i.e., test values and intermediate times) are left to the discretion of the user of the test method.

One test method for anode potential evaluation and two test methods for anode current capacity evaluations are described.

The actual values obtained in these tests should not be used for design purposes because they represent laboratory testing.

This procedure can be validated by using zinc anode samples as a reference in the test to verify results of aluminum anodes tested. Zinc samples shall be as defined in ASTM B 418 Type I (Vol 02-Q4)¹ or Military Specification MIL-A-18001² for zinc anodes.

This procedure was evaluated by testing alloys of Al- Zn-Sn, Al-Zn-Hg, Al-Zn-In-Mg, and MIL-A-18001 zinc of the respective nominal alloy composition ranges shown in Table 1. The results of the test are reported in paper #346 presented at CORROSION/84.³

The precision of the test has not been validated. The scatter in the test results is considered to result from heterogeneities in aluminum alloy anode materials in general, as tested, rather than the test method itself. Only anode materials exhibiting good, reproducible performance (in accordance with this test method) meeting manufacturer or user specifications are acceptable.

⁽¹⁾ ASTM International, 100 Barr Harbor Dr., West Conshohocken, PA 19428-2959.

⁽²⁾ Drill bit No. 25 and 10-24 tap are U.S. standards for preparing a threaded hole for a standard 10-24 screw which is 4.826 mm in diameter. The closest metric equivalent is an ISO M5 screw (5 mm in diameter) with appropriate tap and starter drill bit size.

⁽³⁾ Department of Defense Single Stock Point (DODSSP), 700 Robbins Ave., Building 4/Section D, Philadelphia, PA 19111-5098.

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