Both the acoustic emission (AE) and corrosion potential fluctuation were monitored for
chloride stress corrosion cracking (SCC) of sensitized Type-304 stainless steel plate under bi-axial
stress states. Branched SCCs were produced from rectangular-shaped corrosion pits initiated by
falling-off of surface grains and filled with chromium oxide in 30mass% MgCl2 solution (363K).
Both the AE and potential fluctuation were simultaneously detected during pit formation and SCC
growth. Two types of AE (Type-I and Type-II) were monitored. Type-I AEs with higher frequency
components were detected during the pit growth and supposed to be produced by falling-off of surface
grains due to intergranular attack, while a number of Type-II AEs (approximately 12,500 counts) with
low frequency components were detected during SCC propagation and supposed to be produced by
cracking of the chromium oxy-hydroxides. Though the AEs detected during SCC test are not always
the primary AEs from the SCC itself, secondary AEs can be usefully utilized to monitor the SCC
initiation and propagation as well as the corrosion potential fluctuation.
Influence of Alloying Elements on the Susceptibility of Austenitic Stainless Steels to Chloride Stress Corrosion Cracking