Galvanic Coupling Effect on Pitting Corrosion of 316L Austenitic Stainless Steel Welded Joints

The aim of this work is to display the effect of the chemical composition of the filler metal (ER316LN and ER308LN) on the corrosion resistance of 316L austenitic stainless steel welded joints, performed using GTAW process. The redistribution of chemical elements from the base metal and from the filler metal in the fusion zone during the welding operation produces a variation in the microscopic structure along the welded joint. The latter comprises distinct microstructural zones identified as fusion zone, fusion line (partially melted zone), heat affected zone, and the unaffected base metal with their own electrochemical response. Our results revealed that the base metal constitutes the anodic region in the welded joint, while the fusion zones behave as the cathodic part protected against corrosion. From the electrochemical corrosion tests, it is concluded that the welded joint 316L/ER308LN exhibits a better resistance to pitting corrosion than the welded joint 316L/ER316LN, but is less resistant to corrosion by dissolution.

Automated summary

This study examines the effect of the chemical composition of filler metals on the corrosion resistance of welded joints using GTAW process. The redistribution of chemical elements during welding operation creates variations in microscopic structure, with distinct microstructural zones identified. Results show that base metal acts as the anodic region in the welded joint, while fusion zones act as the cathodic part protected from corrosion. Corrosion tests revealed that 316L/ER308LN welded joint has better resistance to pitting corrosion, though it is less resistant to corrosion by dissolution compared to 316L/ER316LN welded joint.