Corrosion electrochemical behavior of Cu-Ag alloy with different grain size in Na_2SO_4 media

Cu-Ag alloy powders in nano-size were obtained by aqueous reducing method and the nanocrystalline Cu-Ag bulk alloy was prepared through hot pressing with the temperature at 650 ℃ in vacuum.The corrosion electrochemical behavior of the alloy was compared in Na2SO4 media with the coarse grained Cu-Ag bulk alloy prepared by conventional powder metallurgy.The results of corrosion potential curves showed that corrosion potential decreased and therefore corrosion tendency aggravated when grain size was refined.The results of potentiodynamic polarization curves(PPC) showed that corrosion current densities of alloy increased and therefore corrosion rates become faster when grain size was refined.Passivation was unable to appear with increment of corrosion potential in Na2SO4 media.The results of electrochemical impedance spectroscopy(EIS) showed that charge transfer resistance decreased and therefore corrosion rates became faster when grain size was refined.The corrosion processes of Cu-Ag alloy with different grain size were controlled by the electrochemical reactions.The corrosion of nanocrystalline Cu-Ag alloy was uniform and the corrosion of coarse grained CuAg alloy was non-uniform.