Corrosion resistance of dilute CuMg alloys at elevated temperature

In comparison with CuAl (Al: 0.2 and 0.5 wt.%) alloys, corrosion resistance (CR) of CuMg (Mg: 0.12 and 0.34 wt.%) alloys was studied at 673–1173 K in atmospheric O2. All the samples were pre-annealed at 873 K in atmospheric H2. The CR of CuMg alloys at 673–973 K is improved in contrast to a pure Cu but much poorer than that of CuAl alloys, while the improvement can hardly be observed for CuMg alloys at and above 1073 K, which is similar to CuAl alloys. The poorer CR of CuMg alloys compared with that of CuAl alloys at 673–973 K is largely attributed to the incorporation of Cu in the MgO surface layer and the low Pilling-Bedworth ratio of CuMg–O system smaller than unity, and the vanishing of CR for CuMg alloys at and above 1073 K is ascribed to the instability of the MgO layer at the Cu2O/CuMg interface.