THE CONFLICTING ROLES OF COMPLEXING AGENTS ON THE CORROSION OF COPPER-NICKEL-ALLOYS IN SULFIDE POLLUTED SEAWATER

Five copper-nickel alloys with nickel contents ranging from 0 weight percent (w/o) to 100 w/o were electrochemically investigated in sulfide polluted seawater (0 to 100 ppm S=). In addition a chromium modified copper-nickel alloy (CDA 722) was also investigated. The purpose of this research is to investigate the effect of both the nickel content and the sulfide ion concentration under a simulated impingement condition. It is found that CDA 722 performs as well as CDA 715 and better than CDA 706 under impingement conditions in both polluted and unpolluted seawater. In addition, three different complexing agents were investigated. It is found that fuchsin or EDTA can have a beneficial effect in reducing the corrosion rate and a combination of two complexing agents can result in a deleterious effect which can explain the premature failures of copper-nickel alloys often reported in the literature.