The reaction of nickel with SO2 + O2/SO3 at 500–900°C

The reaction of high purity nickel with SO2 + O2 mixtures at 500–900°C has been studied. Measurements have been done in gas mixtures with different SO2/O2 ratios and as a function of the total gas pressure of the system. Rapid corrosion rates are observed under conditions where NiSO4 may be formed on the scale surface and the primary reaction products are NiO and Ni3S2. Corrosion rates are faster when the Ni specimens are surrounded by a Pt catalyst. It is concluded that the reaction mechanism involves an SO3 adsorption equilibrium on the surface followed by formation of NiSO4. The sulfate, in turn, reacts with nickel diffusing rapidly in a sulfide network in the scale to give NiO and Ni3S2.