The effect of sodium sulphate on the corrosion of manganese at 600-800°C

The effect of Na2SO4 on the oxidation of pure Mn has been studied under a mixed oxygen-SO2 atmosphere in the temperature range 600-800°C. The presence of the salt, in spite of the large scattering of the kinetic data, shows a remarkable increasing effect on the metal oxidation rate at 700 and 800°C, whereas at 600°C no accelerated oxidation has been observed. A thermodynamic description of the Mn-O-S system and of the interactions between the oxides scale and the sodium sulphate deposit is presented. The calculations indicate that the formation of a molten MnSO4-Na2SO4 mixture is likely to occur at 700 and 800°C, supporting a low temperature hot corrosion (LTHC) mechanism for the accelerated corrosion.