Effect of Alloying on the Resistance of Cu-1 0% Ni Alloys to Seawater Impingement

Cu-Ni castings and wrought pipes nominally contain 1% Fe to 2% Fe, which is added to improve the Cu-Ni alloy's erosioncorrosion resistance. After fabrication, Cu-Ni products are solution heat-treated to dissolve the iron uniformly andform a single-phase alloy. During welding, however, iron can precipitatefrom solid solution onto grain boundaries in the heat-alfected zones (HAZ). During seawater service, these iron-rich precipitates can dissolve preferentially (galvanically), leading to intergranular corrosion of the HAZ. The present report described 90-10 Cu-Ni alloys in which different soluble elements were substitutedfor iron. Jetimpingement testing in filtered natural seawater showed that 2% In also promoted improved erosion-eorrosion resistance. Because indium is very soluble in copper, it should not precipitate in the HAZ dUring welding and cause intergranular corrosion of the HAZ dUring seawater service. The present study reviewed the literature on the mechanisms by which iron is believed to improve the erosion-eorrosion resistance, and proposed a different model based on doping of the thin surface oxidefzlm.