This paper discusses the mechanism of chloride SCC of sensitized and non-sensitized
Type-304 stainless steel based on the data obtained by simultaneous monitoring of AE and corrosion
potential fluctuation (CPF). The steel produced transgranular SCC via corrosion pits filled with
corrosion product (chromium oxy-hydroxides) in 35 mass % MgCl2 solution. Both the pitting
corrosion and transgranular SCC did not produce primary AEs due to anodic dissolution, while they
generated rapid drop (RD) type CPF. We, however, detected the secondary AEs from hydrogen gas
evolution and fracture of corrosion products. Hydrogen gas was found to produce AE with single
frequency component, while the fracture of corrosion products produced AEs with broad frequency
components. The sensitized steel produced primary AEs due to the falling-off of grains as well as the
secondary AEs. Microscopic progression of SCC was consistently interpreted by the timing and
time-lag of AEs and CPFs.
Noise Analysis of Corrosion Potential of Type 304 Stainless Steel in MgCl2 Solution