Effect of Alloy Structure, Hydroxide Concentration, and Temperature on the Caustic Stress Corrosion Cracking of Austenitic Stainless Steels

Abstract

Abstract Caustic stress corrosion cracking (SCC) experiments have been conducted on Type 304, 304L, 316, 316L, and USS 18-18-2 stainless steels. The environments used were deoxygenated 50% NaOH solution at 316 and 371 C (600 and 700 F), deoxygenated 10% NaOH solution at 316 C and atmospheric boiling [~149 C (300 F)] 50% NaOH. The effect of grain size, cold work, and sensitization has been studied. Metallurgical structures were examined with light microscopy and the accelerated Strauss test. Exposed specimens were studied with the light microscope and the fracture surfaces were studied with the scanning electron microscope (SEM). Variations in crack morphology were observed with caustic concentration and alloy content. Certain sensitization treatments were the only conditions identified in Type 304 as beneficial in increasing the high temperature caustic stress corrosion resistance.