Parametric Evaluation of Susceptibility of Cu-Ni Alloys to Sulfide Induced Corrosion in Sea Water

Experiments were performed to determine susceptibility of 90/10 and 70/10 Cu-Ni alloys to sulfide induced corrosion as related to sulfide concentration, sea water velocity, and duration of sulfide exposure. All exposures were conducted in fresh sea water, and the range of experimental variables included sulfide concentration (from sodium sulfide) from 0.007 to 0.25 mg/L, sea water velocity after sulfide exposure from 0.5 to 5.3 m/s, and sulfide exposure times from 1 to 90 days. Results showed that both alloys undergo localized attack in sea water environments with as little as 0.007 mg/L sulfide. The velocity dependence of active attack was minimal in the range tested. Duration of sulfide exposure, particularly at low sulfide concentrations, is a key factor in causing localized corrosion in these alloys and in the degree of attack experienced. On the basis of long term continuous low concentration sulfide exposure, 70/30 Cu-Ni appears to undergo less severe attack than that seen with 90/10 Cu-Ni.