External SCC of Austenitic Stainless Steels in Atmosphere Containing Sea Salt Particles

Base on failure analyses of external IGSCC of Type 304 in an atomosphere containing sea salt particles and SCC test results by a wet and dry salt spray method, the following facts have been obtained:(1) External IGSCC of Type 304 vessels used without any surface insulations occurs due to a combination of the following conditions, (i) sensitization at grain boundaries, (ii) residual stress, (iii) an atmosphere containing sea salt particles, and (iv) rusting on the surfaces of the vessel.(2) The sensitization of Type 304, essentially the susceptibility to IGSCC is remarkably increased by cold work.(3) When the reactivation ratio of Type 304 is above approx. 5% in EPR tests, Type 304 is susceptible to external IGSCC.