Passivity breakdown and pitting on pure copper, the assumed material for the canisters for the isolation of high-level nuclear waste in Sweden, has been studied in simulated, sulphide- and chloride containing granitic rock groundwater and the data are interpreted in terms of the Point Defect Model (PDM). The results indicated that a sulphide barrier layer forms on the copper surface, and that chloride ion can induce passivity breakdown, and hence induce the development of localized corrosion damage (LCD), such as pitting corrosion, on the canister surface. In this study, the effects of chloride concentration (0.01–5 M), solution pH (= 8–10), and temperature (22–82ºC) on the pitting corrosion of copper in simulated repository ground water have been studied. The principal findings of the study are summarized in the executive summary written by the authors.