INFLUENCE OF SURFACE FINISHES ON CORROSION BEHAVIOR OF CN108 ALLOY FOR CONDENSER TUBES IN SEA-WATER

The influence of surface finish on corrosion behaviour of CN 108 alloy in sea water and the reliability of the Shell test as a criterion of acceptance were investigated. The Shell test performed on samples with different surface finishes demonstrated that this test is mainly influenced by the presence of a manganese rich oxide. Corrosion tests in flowing chlorinated sea water using a once-through loop demonstrated that there was no evidence of any paramount difference in the corrosion behaviour between samples with a manganese-rich thermal oxide on the surface, which do not conform to the Shell test, and samples abrasively cleaned, which conform to the Shell test. In highly chlorinated sea water abrasive cleaning mitigated localized corrosion and a ferrous sulphate pretreatment decreased the corrosion more pronouncedly.