Corrosion behavior of three Ag-50Cu alloys prepared bydifferent processes in NaCI solutions

Corrosion behavior of two nanocrystalline bulkAg-50Cu alloys and one coarse-grained counterpart pre-pared by liquid-phase reduction （LPR）, mechanical alloy-ing （MA） and powder metallurgy （PM） methods,respectively, were investigated in NaC1 solutions. Theywere finished by means of PARM273A and M5210 elec-trochemical apparatus through potentiodynamic polariza-tion method and electrochemical impedance spectroscopy（EIS） technique. The results show that corrosion rates ofthree Ag-50Cu alloys increase with the increment of NaC1solution concentrations. Corrosion rates of LPRAg-50Cualloy are a little higher than those of PMAg-50Cu alloy,but evidently lower than those of MAAg-50Cu alloy. Thedifference in corrosion rates is attributed to the largereduction in the grain size and homogeneous microstruc-ture of nanocrystalline alloys. Passive current densitiesdecrease and afterward increase for PMAg-50Cu alloy,decrease for MAAg-50Cu alloy, and increase for LPRAg-50Cu alloy with the increment of NaCl solution concen-trations. After the grain sizes are refined, passive currentdensities become lower.