Electrochemical properties of coarse and nano-grained pure copper can be modified and improved effectively through applying cyclic potentiodynamic passivation (CPP) treatment. It is found that the success of this method depends up to a large extent on grain size. Eight passes of accumulative roll bonding processing are successfully used at room temperature to produce nano-grained pure copper. Transmission electron microscopy image and selected area diffraction pattern both attest to the occurrence of intense grain refinement under the influence of aforementioned process, in which an average grain size <100 nm is attainable. Using several electrochemical characterization methods reveals that CPP treatment fully exploits potentials of nano-grained samples to form a dense and thick protective passive film. It is speculated that high-quality passive layers relate to the presence of high-density structural defects on the surface of nano-grained samples.
