Investigations on the Corrosion of Flash Chamber Floor Plates in a Multistage Flash Desalination Plant

This article presents the results of an investigation on the corrosion of flash chamber floor plates in a multistage flash (MSF) desalination plant. In an MSF plant, desalinated water is produced by flashing deaerated seawater in successive flash chambers under reduced pressure. The flash chamber floor plates were made of carbon steel with AISI type 317L stainless steel (UNS S31703) internal cladding. The thickness of the carbon steel and cladding was 8.5 and 3 mm, respectively. Approximately four years after the plant was commissioned, indications of corrosion processes, in the form of numerous red-colored spots, were noticed on the floor plates. The cause of corrosion was determined by examining the operating history, conducting an on-site visual examination coupled with an in situ material analysis of the floor plates ( through the use of a portable alloy analyzer), and analyzing the corrosion products with energy-dispersive X-ray analysis. The corrosion was attributed to frequent shutdowns and fairly long periods of stagnant high-chloride water on the floor plates during shutdown. Recommendations are given to prevent/minimize such failures.