Effect of grain orientation on corrosion morphology of copper-nickel alloy

The corrosion failure analysis of copper-nickel alloy pipes was mostly focused on the surface electrochemical corrosion behavior and the correlation between the structure of the passive film and the corrosion resistance. However, the effect of the surface microstructure of the copper-nickel alloy pipe on the corrosion resistance has not been clarified by now. In this paper, both the scanning electron microscopy with back scattered electron diffraction (SEM-EBSD) and atomic force microscopy (AFM) were utilized to characterize the orientation and corrosion morphology of the grains of the copper-nickel alloy pipe by indentation-tracking, so as to reveal the corrosion behavior and corrosion morphology evolution of the differently oriented grains. The results show that the corrosion depth of the grains increases and the corrosion morphology changes from scallop-like to step-like or tetrahedral convex shape as the angle between the grain orientation and the direction decreases. It is directly related to the surface energy of the grains, which is in line with the terrace ledge kink (TLK) model. © 2022, China Science Publishing & Media Ltd. All right reserved.