Detection and characterization of chloride induced stress corrosion cracking on SS304 under perlite thermal insulation

Abstract

Abstract. Austenitic stainless steel (ASS) type SS304 has been extensively employed in various sectors because of its good structural strength and corrosion resistance. These steels are susceptible to chloride-induced stress corrosion cracking (CISCC), particularly by the effect of chloride corrosive environment under thermal insulation. Corrosive environment formed by external sources or condensation due temperature differences under thermal insulation as a result of inadequate maintenance or unfavourable climatic conditions. It causes localised corrosion and leads to catastrophic failure under the action of tensile stress. The objective of the research was to detect the chloride-induced stress corrosion cracking on SS304 under thermal insulation. This study simulated a real corrosive environment using water containing chloride ions on U-bend samples to estimate the susceptibility and assess CISCC under the drip test method. SS304 as-received (AR) and sensitized (SEN) over-stressed U-bend samples were tested as per ASTM C692 standard. Samples were exposed to 0.1, 1.0, and 3.5 wt. % of NaCl concentrations under perlite thermal insulation and tested at 90oC. Under high chloride concentrations, SEN samples were susceptible more and showed little evidence of crack initiation. The rest of the concentrations showed no evidence of crack, but they showed tiny localized corrosion near the dripping zone. The characteristics of the material structure and the corrosion mechanism were described in a pictorial view.