Corrosion behavior of three Ag-50Cu alloys prepared by different processes in NaCl solutions

Corrosion behavior of two nanocrystalline bulk Ag-50Cu alloys and one coarse-grained counterpart prepared by liquid-phase reduction (LPR), mechanical alloying (MA) and powder metallurgy (PM) methods, respectively, were investigated in NaCl solutions. They were finished by means of PARM273A and M5210 electrochemical apparatus through potentiodynamic polarization method and electrochemical impedance spectroscopy (EIS) technique. The results show that corrosion rates of three Ag-50Cu alloys increase with the increment of NaCl solution concentrations. Corrosion rates of LPRAg-50Cu alloy are a little higher than those of PMAg-50Cu alloy, but evidently lower than those of MAAg-50Cu alloy. The difference in corrosion rates is attributed to the large reduction in the grain size and homogeneous microstructure of nanocrystalline alloys. Passive current densities decrease and afterward increase for PMAg-50Cu alloy, decrease for MAAg-50Cu alloy, and increase for LPRAg-50Cu alloy with the increment of NaCl solution concentrations. After the grain sizes are refined, passive current densities become lower.