Mechanisms of hot corrosion of pure nickel at 700°C: Influence of testing conditions

The hot corrosion behaviour of pure nickel was investigated at 700 °C to highlight the influence of testing conditions (composition of the atmosphere and presence or not of a Na2SO4 deposit) on the mechanisms of hot corrosion. The influence of SO2/SO3 inward transport through the porous NiO growing scales was studied by exposing nickel in synthetic air and in synthetic air + 0.5% SO2/SO3 without Na2SO4. The addition of Na2SO4 decreased the pO2 and the pSO3 at the sample surface, which promoted the formation of Ni-S liquid solution at the metal/scale interface. A sufficient pSO3 was required to stabilize liquid Na2SO4-NiSO4 solutions and simulate Type-II hot corrosion conditions.