Influence of sulfide concentration on the corrosion behavior of pure copper in synthetic seawater

Taniguchi, Naoki ; Kawasaki, Manabu*

Corrosion rate and stress corrosion cracking (SCC) behavior of pure copper under anaerobic condition were studied by immersion test and slow strain rate technique (SSRT) test in synthetic seawater containing NaS. As the results of the immersion test up to 730 days, the corrosion rate of pure copper was strongly depended on sulfide concentration and was estimated to be less than 0.6 m/y for 0.001M-NaS, 2-4 m/y for 0.005M-NaS and 10-15 m/y for 0.1M-NaS. The results of SSRT test showed that obvious SCC occurred in relatively high sulfide concentration over 0.005M. According to these test results, copper is possible to exhibit superior corrosion resistance in low sulfide concentration of less than 0.001M because of very low corrosion rate and no SCC. The long term corrosion depth due to sulfide was estimated from the sulfide flux to the overpack surface assuming the diffusion of sulfide through bentonite, and the overpack lifetime was evaluated as a function of sulfide concentration in groundwater.