Evaluation of inter-granular corrosion susceptibility in 316LN austenitic stainless steel weldments

The inter-granular corrosion resistance of 316LN austenitic stainless steel welding joints for an ITER Correction Coil case in the as-welded and post weld heat treatment (PWHT) condition were systematically investigated. Measurements were performed in accordance with the standard ASTM A262 and via double loop electrochemical potentiokinetic reactivation. The pitting corrosion resistance was determined for specimens immersed in sodium chloride solutions. In addition, the effect of microstructural characteristics on the corrosion resistance was analyzed. The results revealed that the dendrite size in the weldment slightly increased after PWHT. Moreover, the corrosion test results showed that the inter-granular corrosion resistance of the PWHT joint is significantly lower than that of the other specimens due to the element segregation in the weldments. However, all the specimens exhibite excellent pitting corrosion resistance, as indicated by the potentiodynamic polarization curves.