Correlations between the kinetics and the mechanisms of hot corrosion of pure nickel at 700 °C

Abstract This study investigates the kinetics of hot corrosion of pure nickel exposed to different testing conditions at 700 °C. Whereas nickel underwent pure oxidation when exposed to synthetic air only, the addition of 0.5% SO2/SO3 induced oxidation-sulphidation and considerably increased the corrosion kinetics. In the presence of sodium sulphate (Na2SO4), Ni-S liquid solutions systematically formed at the metal/scale interface. This was attributed to the shielding effect of Na2SO4 implying negative pO2 and pSO3 gradients from the gas/salt interface towards the scale/salt interface. The influence of thermal cycling as well as the testing method (i.e. half-embedding and salt-recoating) was also elucidated.