High temperature oxidation behaviour of Ag-36.35Â wt.% Zn and Ag-38.50Â wt.% Zn-0.60Â wt.% Al

Ag-36.35 wt.% Zn and Ag-38.50 wt.% Zn-0.60 wt.% Al were oxidised in air at 450-650 °C up to 48 h. The oxidation kinetics of both alloys were parabolic with the lower rate constant for the latter alloy. After oxidation for 48 h, thermal oxide scale on Ag-36.35 wt.% Zn was ZnO at all studied temperatures. When 0.60 wt.% Al was added to Ag-38.50 wt.% Zn, ZnO and ZnAl2O4 were formed at all studied temperatures. Al2O3 was evidently observed at 550 and 650 °C. The formation of Al-containing oxides helped reduce the oxidation rate of Ag-38.50 wt.% Zn-0.60 wt.% Al.