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

Corrosion rate and stress corrosion cracking (SCC) behavior of pure copper under anaerobic conditions were studied by immersion tests and slow strain rate tests (SSRT) in synthetic seawater containing Na2S. The corrosion rate was increased with sulfide concentration both in simple saline solution and in bentnite–sand mixture. The results of SSRT showed that copper was susceptible to intergranular attack; selective dissolution at lower sulfide concentration (less than 0.005 M) and SCC at higher sulfide concentration (0.01 M). It was expected that if the sulfide concentration in groundwater is less than 0.001 M, pure copper is possible to exhibit superior corrosion resistance under anaerobic condition evident by very low corrosion rates and immunity to SCC. In such a low sulfide environment, copper overpack has the potential to achieve super-long lifetimes exceeding several tens of thousands years according to long-term simulations of corrosion based on diffusion of sulfide in buffer material.