Effect of pH Values and Microstructures on Corrosion Behavior of Ag-25Cu Alloys in NaCl Acidic Solutions

The effect of pH values and microstructures on the corrosion behavior of one coarse grained and two nanocrystalline Ag-25Cu alloys prepared by three kinds of methods including powder metallurgy (PM), liquid phase reduction (LPR), and mechanical alloying (MA) was investigated in NaCl acidic solutions. The corrosion rates slightly increase in the range of pH values from 7 to 5, but evidently when the pH values are less than 5. Furthermore, the corrosion rates increase after the nanocrystallizations and the nanocrystalline LPR Ag-25Cu alloy corrodes faster than the nanocrystalline MA Ag-25Cu alloy. All three Ag-25Cu alloys produce the passive phenomena and the passive films belong to n-type semiconductors. The passive current densities decrease in the order of PM Ag-25Cu, LPR Ag-25Cu, and MA Ag-25Cu alloys.