Effect of pre-oxidation treatment on the corrosion behaviour of Ni-Ti alloys in eutectic (Li, K)2CO3 mixture at 650(degree)C

The effect of pre-oxidation treatment at 650(degree)C in air on the corrosion behaviour of binary Ni-Ti alloys containing 5, 10, and 15 wt-%Ti in eutectic (Li, K)2CO3 at 650(degree)C in air has been investigated. The results indicate that the pre-oxidation of the alloys can produce an almost pure TiO2 scale. Nevertheless, this TiO2 scale cannot hinder the formation of NiO outside and beneath the TiO2 scale during subsequent molten salt corrosion. The corrosion rates of the alloys decrease with increasing content of titanium in the alloys. The corrosion of the alloys proceeds mainly by inward diffusion of oxygen through the TiO2 layer, forming large quantities of NiO beneath the TiO2 layer. Compared with Ni-5Ti and Ni-10Ti, the formation of NiO on Ni-15Ti is inhibited significantly, especially in the initial stages.