The stress corrosion cracking (SCC) of pure copper poly- and single crystals in NaNO2 solutions was investigated potentiostatically by the slow strain rate technique. The susceptibility to SCC has a maximum in 1kmol·m-3 NaNO2 solution of 7.3-7.5pH, at the strain rate below 1.67×10-5S-1. In this solution, a close correlation was found between the SCC and anodic polarization behavior of pure copper: The potential range for SCC occurrence was 0-100mV (SCE), nearly corresponding to that of passivity/transpassivity transition where the formation or rupture of black tarnish film (Cu2O) occurred. The fractographic results showed that many cracks nucleated from the specimen surfaces with frequent slip-steps, producing the tarnish film. The crack propagation was predominantly transgranular, along ‹110› direction on {110} plane. The evidence introduced here supports an anodic dissolution mechanism for the transgranular SCC of pure copper in NaNO2 solutions, including a tarnish rupture mechanism.
