Corrosion of copper in anaerobic groundwater in the presence of SRB

Copper is used in various applications that are in contact with natural environment. These environmental conditions favor and enable formation of biofilms by naturally occurring microbes. Copper has also been the corrosion barrier of choice for the nuclear waste storage canisters in the Finnish nuclear waste disposal program. The copper canisters should have lifetimes exceeding 100 000 years to prevent the release of radioactive nuclides to the environment. Copper is commonly considered to be immune to corrosion in oxygen-free water. This is an important argument for using copper as a corrosion protection in the planned canisters for encapsulation of spent nuclear fuel in Sweden and Finland. However, microbial biofilm formation on metal surfaces can enhance corrosion in various conditions and provide conditions where corrosion would not otherwise occur. Microbes can generate conditions that enhance corrosion e.g. through the alteration of pH and redox potential, excretion of corrosion inducing metabolites, direct or indirect enzymatic reduction or oxidation of corrosion products and formation of biofilms that create corrosive microenvironments. Corrosion may reduce lifetime of equipment and structures. Microbial metabolites are known to initiate, facilitate, or accelerate general corrosion or localized corrosion, galvanic corrosion, intergranular corrosion and also enable stress corrosion cracking. Sulfate reducing bacteria (SRB) that produce sulfide are present in the repository environment. Sulfide is known to be a corrosive agent for copper. Here we show results from corrosion of copper in anaerobic simulated ground water in the presence of SRB enriched from the disposal site. Electrochemical measurements were proven to be useful in monitoring the initiation and progression of general and localized corrosion of copper.