Pitting Corrosion Studies on Fusion Zone of Shielded Metal Arc Welded Type 316LN Stainless Steel Weldments

During welding of 316L stainless steel (SS), heat-affected zone (HAZ) is susceptible to sensitisation and fusion zone is susceptible to pitting corrosion in stainless steel welds. High-nitrogen electrodes with 0.045-0.055 wt% C and with different Cr contents were used for welding of prototype fast breeder reactor components. As-welded and thermally aged (823 K for 2 h) weldments of type 316LN SS with different N contents made by arc welding were studied for localised corrosion. ASTM A262 Practice A and E tests and double-loop electrochemical potentiokinetic reactivation studies on as-welded and thermally aged specimens revealed the absence of sensitisation in the HAZ and in fusion zone. However, pitting potential of the weldments was found to vary with the concentration of N + Cr + Mo in fusion zone and found to be lower in the thermally aged samples. The correlation between weld microstructure, alloying elements and pitting corrosion behaviour has been discussed.