Understanding the interfacial diffusion behavior of alloying elements between electrodeposited nickel coating and 347H stainless steel interface in 700 °C molten chloride salt

Nickel (Ni) coating is a promising strategy to mitigate high-temperature corrosion of 347H stainless steel (SS) in molten chloride salts for next-generation concentrated solar power (CSP) systems. However, the interfacial diffusion behavior of alloying elements and underlying degradation mechanisms remain unclear. This work investigates the interdiffusion of main elements and degradation characteristics of electrodeposited Ni coatings on 347H SS substrates. Results reveal that the interdiffusion of Ni and Chromium (Cr) at the interface leads to vacancy accumulation and void formation. In addition, the ingress and diffusion of sulfur (S) result in the formation of MnS precipitates. The deposition of external Fe in molten salts on the sample surface gives rise to the formation of a barrier layer. All these factors lead to the reduction in diffusion coefficients of Cr and Ni with prolonging the immersion in chloride melts, correspondingly inhibiting the corrosion of 347H SS in molten chloride salts.