Stress corrosion cracking of Inconel 600 in aqueous solutions at elevated temperature .1. Initiation and inhibition of corrosion cracking process

The study reported here has been designed to determine the influencing effect of sulphate ions on chloride induced crack initiation of Inconel 600 using compact tension (CT) samples in chloride containing aqueous solutions at elevated temperature up to 250 degrees C. The results show that sulphate ions retard the effect of chloride ions on crack initiation in hot water up to 250 degrees C. Intergranular stress corrosion cracking (IGSCC) occurs in both chloride solution and in chloride solution with relatively low concentration of sulphate ions. The mode of cracking changes from brittle to ductile failure due to the influence of inhibiting concentration of sulphate. The results are interpreted in the light of repassivation-dissolution controlled mechanism which is the predominant mechanism. The inhibiting effect of sulphate ions on the initiation of corrosion cracking is attributed to the repassivation and the formation of Fe-Cr-spinel oxide layer which is stable also at higher temperature.