On the corrosion behaviour of magnesium and its alloys using electrochemical techniques

Measurements of Tafel slopes and impedance are used to examine the corrosion aspects of magnesium and its alloys AZ 31 (Mg---Al---Zn), AZ61 (Mg---Al---Zn) and AP 65 (Mg---Al---Pb) in aqueous magnesium perchlorate solution. Impedance studies show that the electrode/ electrolyte interfacial mechanism is activation-controlled. The results are explained in terms of stability of the film on the metal surface and on the influence of the specific alloy constituents on the hydrogen overvoltage. Variation of anodic potential during impedance measurements on magnesium alloys indicates a stepwise decrease in the charge-transfer resistance with gradual increase in anodic potential.