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 p ercent (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 th is research is to investigate the effect of both the nickel content an d the sulfide ion concentration under a simulated impingement conditio n. It is found that CDA 722 performs as well as CDA 715 and better tha n CDA 706 under impingement conditions in both polluted and unpolluted seawater. In addition, three different complexing agents were investi gated. It is found that fuchsin or EDTA can have a beneficial effect i n reducing the corrosion rate and a combination of two complexing agen ts can result in a deleterious effect which can explain the premature failures of copper-nickel alloys often reported in the literature.