Failure investigation of heat exchanger plates due to pitting corrosion

A mid country textile mill submitted a set of 316L stainless steel heat exchanger plates of its power generation system with primary and secondary loop water samples to investigate the cause of frequent perforation and fouling at open circuit cooling water side. The detailed study was carried out to determine the actual system fault which included chemical analysis of water samples, metallurgical and electrochemical testing of 316L plates in the provided water samples. It was evaluated that chloride contents in the open circuit feed water and non-expert approach to understand and control of system parameters were the root cause of this failure. The electrochemical cyclic polarization and potentiostatic test results confirmed the susceptibility of 316L SS plates to severe pitting corrosion in CT feed, and CT bleed water than auxiliary and engine jacket water due to high level of chloride contents.