Enhanced corrosion resistance of a Cu-10Ni alloy in a 3.5 wt% NaCl solution by means of ultrasonic surface rolling treatment

Cu-10Ni alloy with a gradient nano-structured surface layer was synthesized by ultrasonic surface rolling process (USRP). The microstructure and mechanical properties of the nanosurface layer were characterized by Xray diffractometry (XRD), microhardness testing, scanning electron microscope (SEM) and transmission electron microscope (TEM). The corrosion behavior of the USRPed and coarse-grained (CG) Cu-10Ni alloy in a 3.5 wt% NaCl solution was investigated. The results showed that the topmost surface possessed an average grain size of 70 nm, and the corresponding surface hardness increased by 80% after USRP treatment. Additionally, the electrochemical test results showed that the USRPed Cu-10Ni alloy exhibits enhanced corrosion resistance relative to that of the CG sample in a 3.5 wt% NaCl solution. The higher corrosion resistance of the nanograined Cu-10Ni alloy was attributed to the nanograined surface promoting the formation of a passivation film on the surface during the corrosion process, which can effectively prevent further corrosion. This study demonstrates that the hardness properties and corrosion resistance of Cu-10Ni alloys can be improved simultaneously by means of surface nanocrystallization.