The scaling behavior of a monophase Cu-3.36 wt.% Co Alloy at 700–1000°C

The oxidation of a dilute copper-cobalt alloy at high temperatures has been studied to examine the effect of the cobalt addition on the different aspects of copper oxidation. The alloy oxidizes parabolically with a rate constant generally smaller than that of pure copper but approaching it at higher temperatures. The scale is essentially composed of copper oxides (CuO is observed only at 700°C) containing a small concentration of dissolved cobalt and particles of CoO in the inner region of the scale while internal oxidation is observed at all temperatures. The oxidation behavior of the alloy is examined with reference to the known factors affecting the corrosion of binary alloys. A theoretical calculation of the parabolic rate constant for pure copper and for the alloy with cobalt is also presented. Possible reasons for the observed deviation from the effect of doping as predicted on the basis of a simple model for the defect structure of Cu₂O are pointed out.