Impressed Current Laboratory Testing of Aluminum and Zinc Alloy Anodes
|Publication Date:||5 October 2012|
This standard test method describes a laboratory procedure for determining the potential and current capacity characteristics of aluminum and zinc 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 B4184 or Military Specification MIL-DTL-18001 for zinc anodes.
This procedure was evaluated by testing alloys of Al-Zn-Sn, Al-Zn-Hg, Al-Zn- In-Mg, and MIL-DTL-18001 zinc of the respective nominal alloy composition ranges shown in Table 1. The results of the test are reported in Paper No. 346 presented at CORROSION/84.1
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) and meeting manufacturer or user specifications are acceptable.
Al/Zn/In alloys have been found suitable for this test method (see ANSI/ NACE SP0115/ISO 15589-2 and Military Specification MIL-DTL-24779).5