Effect of surface oxidation on corrosion mechanism of Co–20·8Ni–6Al–10Cu–11Fe cobalt alloy in molten cryolite

Abstract

In this paper, the effect of surface oxidation on corrosion behaviour of Co–20·8Ni–6Al–10Cu–11Fe alloy in molten cryolite is investigated. The samples were produced by casting and then were oxidised at 1000°C for 10, 30 and 70 h respectively. The oxide layers were studied by scanning electron microscope (SEM) and X-ray diffraction (XRD). To determine the corrosion behaviour of the oxidised samples, they were exposed to molten cryolite at 930°C for 20 h. After corrosion, the samples were studied by SEM. The results showed that all the samples corroded, but the sample oxidised for 70 h, was more stable than the other and the other one that oxidised for 10 h, corroded severely.