This paper discusses the process of chloride SCC of sensitized and non-sensitized Type-304 stainless steel based on the simultaneous monitoring of AE and corrosion potential fluctuation (CPF). The steel produced transgranular SCC via corrosion pits filled by corrosion product (chromium oxy-hydroxides) in 35 mass % MgCl₂ solution. Neither the pitting corrosion nor transgranular SCC produced primary AEs due to anodic dissolution process, while they did generate rapid drop (RD) type CPF. However, we detected secondary AEs from hydrogen gas evolution and fracture of corrosion products. Hydrogen gas was found to produce AE with a limited frequency component, while the fracture of corrosion products produced the AE with broad frequency component. The sensitized steel produced primary AEs due to the falling-off of grains as well as secondary AEs from hydrogen gas evolution and the fracture of corrosion products. Microscopic progression of SCC was consistently interpreted by the timing and time-lag of AEs and CPFs.

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