High temperature corrosion mechanism of Ni–5W–6B–28Cr–13Al alloy in simulated MSW incineration environment
Wenchao Ma, Sixuan Zeng, Terrence Wenga
Abstract
In this study, the corrosion behavior of a newly designed alloy (Ni–5W–6B–28Cr–13Al) in simulated municipal solid waste (MSW) incineration atmosphere in the presence of HCl, NaCl, and SO2 under an oxidizing humidity condition at 600 °C was conducted. The combined effects of these aggressive species on corrosion mechanism were elucidated by means of XRD, SEM, EDS, and thermodynamic calculations. The results showed that the contribution to the corrosion rate was in the order of NaCl + HCl > NaCl > HCl. The alloy was rarely corroded without NaCl coating, while the alloy experienced enhanced corrosion attack of 12.183 mg/cm2 under NaCl exposure. In the presence of HCl and NaCl, the accelerated corrosion of the tested alloy reached a maximum mass gain of 75.592 mg/cm2. Both experimental and theoretical results suggested that the corrosion occurred via an active oxidation reaction where the NaCl coating was converted to molten phase which degraded the alloy forming a massive unprotective oxide scales. Nonetheless, the synergistic effect of NaCl and HCl was significantly suppressed by the sulfation after SO2 application of nearly 50% less than the mass change before SO2 application.