Crevice Corrosion of Duplex Stainless Steel Compact Flanges

摘要

Two of three subsea manifolds failed to hold hydrotest pressure during commissioning. Leaks were traced to compact flange hub connections joining multiphase flow meters (MPFMs) to manifold piping. Visual examination following recovery of the MPFMs revealed crevice corrosion of the A182 F51 22Cr duplex stainless steel hub and the UNS N07750 gasket. The water treatment strategy failed to control corrosion by seawater, which entered the manifold during deployment and remained inside for six months during wet parking prior to commissioning. Common alloys used for subsea connections were tested for resistance to crevice corrosion.