MIC Issues in Seawater Cooling of Coated CS/70-30 Cu-Ni

Seawater from the Gulf of Mexico was used as cooling water makeup in an open recirculating cooling system at an industrial plant. Approximately five months after startup, leaks occurred in internally coated carbon steel piping, equipment, and 70-30 Cu-Ni (copper-nickel) condenser tubing. These failures were attributed to aggressive microbiologically influenced corrosion caused by inadequate biocide treatment and stagnant conditions during startup. Corrosion was concentrated on coating defects, including those meeting inspection criteria. Titanium tubing showed bacterial presence without corrosion. Mitigation involved extensive cleaning, flushing, improved biocide control, selective pipe replacement or fiberglass wrapping, and condenser tube plugging/retubing.