Galvanized Bolts’ Impact on Marine Type 316 SS Corrosion

Leakages recently found in chromium (22Cr) duplex steel ring type joint flange assemblies with SS316 gaskets were attributed to crevice corrosion initiated externally from the marine environment. This was unexpected as such flange connections have been in operation for many decades without any corrosion. A comprehensive study was conducted to examine several hypotheses related to the cause of the observed change in corrosion behavior. The root cause of the leakages was identified to be a recent change in fastener material from hot dip galvanized steel to 25Cr duplex steel.