● The corrosion resistance of the NiCrMoAlSi coating is significantly stronger than that of the Inconel 625 coating. ● This superior corrosion resistance primarily originates from the formation of a protective Si-enriched oxide film on the NiCrMoAlSi coating surface. ● Elevated temperatures enhanced the integrity and coverage of this Si-rich oxide film, contributing to improved corrosion protection performance. Hot corrosion behavior of Inconel 625 and NiCrMoAlSi cladding layers beneath deposits of molten KC1-55%ZnCl 2 was systematically studied. Results show that corrosion resistance of NiCrMoAlSi is significantly better than that of Inconel 625, with a mass loss at 550 and 650°C (14.30 and 0.87 mg/cm ², respectively) reduced by 76.40% and 98.99%, respectively. This advantage is attributed to a dense Si-rich oxide film generated on NiCrMoAlSi surface, which effectively interrupts ‘activated oxidation’ corrosion chain reaction by blocking Cl 2 /O 2 infiltration. Increasing temperature has opposite effects on two cladding layers: Inconel 625 experiences 42.4% increment in mass loss at 650°C, due to the accelerated dissolution of Cr, while mass loss of NiCrMoAlSi decreases by 94.0% at 650°C, owing to the high temperature promoting integrity of the Si-rich oxide film. Therefore, NiCrMoAlSi can achieve long-term protection through self-generation of the Si-rich oxide film above 650°C, and is suitable for high-temperature corrosion scenarios such as waste incineration superheater tubes.
Zhang et al. (Sun,) studied this question.