Abstract
Austenitic stainless steels such as Type 304 (UNS $30400) and Type 316 (UNS 31600) are frequently selected for heat exchangers placed in cooling water service. These alloys generally perform well in clean water and are expected to give a long service life with minimal problems. Unfortunately the assumption that cooling waters will be clean is often misleading, and unexpected failures can result from localized corrosion mechanisms such as pitting, crevice corrosion, microbiologically influenced corrosion (MIC), and stress-corrosion cracking (SCC). Localized corrosion may be associated with water chemistry parameters such as temperature and chlorides, deposits that accumulate in the system, microbiological activity, operational factors such as low water velocity and stagnant water after hydrotesting, and variations in steel chemistry at inclusions and welds. An overview of localized corrosion mechanisms for stainless steel is presented along with corrosion tendencies for modem versions of Types 304/316 stainless steels.
