Zinc anodes for cathodic protection are cast from pure zinc (99.995 %) with aluminium and silicon to combat impurities and cadmium to give constant dissolution with loose dispersible corrosion products.
Zinc anodes show an open circuit potential, at temperature -1100 mV or move negative in reference to a Cu/CuSO4 Electrode.
Zinc anodes for soil and freshwater application shall conform to the following Composition :
Aluminium
-0.005% Maximum
Copper
-0.002% Maximum
Iron
-0.0014% Maximum
Lead
-0.003% Maximum
Cadmium
-0.003% Maximum
Zinc
Balance
Zinc anodes for sea water application shall conform to the following Compsition: