純銅のNaNo_2溶液中における応力腐食割れ感受性

概要

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The stress corrosion cracking (SCC) of pure copper poly- and single crystals in NaNO_2 solutions was investigated potentiostatically by the slow strain rate technique. The susceptibility to SCC has a maximum in 1 kmol・m^ <-3>NaNO_2 solution of 7.3〜7.5 pH, at the strain rate below 1.67X10^ <-5>S^ <-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 0〜100 mV(SCE), nearly corresponding to that of passivity/transpassivity transition where the formation or rupture of black tarnish film (Cu_2O) 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 NaNO_2 solutions, including a tarnish rupture mechanism.
1991-08-15