Corrosion of SS 316 Ti Motor-Pump Casings in Deep Water Wells due to Welding Defects

ABSTRACT. A site investigation was conducted on corrosion damage to stainless steel alloy 316 Ti (UNS S31635) motor pump casings installed in deep fresh water wells. The damage consists of full-wall perforation, localized pitting and crack like attack. The corrosion attack was observed in the weld area and heat affected zone (HAZ) of the motor casing longitudinal seam weld. The investigation revealed that small anodic sites were formed on the motor casing surfaces close to the seam weld as a result of poor welding and lack of post treatment. This is confirmed through a comparison of the same material welded using a good welding practice and adequate post treatment and installed in a similar environment. This paper represents the corrosion failure investigation and outlines measures to avoid such failures including precautions to be taken during welding of stainless steel alloys.