The service life of Mg anode cathodic protection systems installed on iron water mains has, in some instances, been significantly less than design calculations would predict. Testing of high-potential Mg alloys from various suppliers using the ASTM G97-89 test method indicates that efficiencies are widely variable and that the life of a Mg anode could be as much as 90% less than calculated, depending on the source of the Mg. The literature shows that various factors such as anode current density, anode oxidation reaction, anolyte chemistry, alloy chemical composition, and alloy microstructure can affect anode efficiency. Municipalities are advised to conduct tests for alloy composition, microstructure, and backfill composition on anodes from industry suppliers in order to ensure anode quality and maximum system life.
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