Corrosion resistance behavior of gradient microstructure induced by punching deformation and recovery treatment on cupronickel alloy surface

In this study, the gradient grain induced by punching deformation and recovery treatment on a cupronickel alloy surface sample were investigated, and their effects on corrosion resistance were measured by atom force microscopy (AFM), X-ray diffraction (XRD), electrochemical measurement, electron work function (EWF), and contact electrical resistance (CER). The cupronickel alloy surface experienced punching deformation for 60 min and recovery at 300 °C for 1 h to produce gradient surface. The grain size measured by XRD is bigger than that measured by AFM, due to X-ray intensity of 95 % produced at the depth of 12–20 μm for the crystal planes of (111), (200), and (220). The gradient grain surface, compared to the original surface, shows a 13.7-fold decrease in passivation current density (i _p), and corrosion potential (E _C) increases by approximately 9.8 %. These results are attributable to the increase in EWF and formation of passivation film with better adhesion and compactness after treatment.