Galvanic corrosion behavior of Cu-Fe-Zn trimetallic couple in acidic media

The galvanic corrosion behavior of Cu-Fe-Zn trimetallic couple and its factors were investigated in acidic chloride solution using electrochemical and numerical methods. Results demonstrated that the potential difference of galvanic couple reflects only the thermodynamic tendency of galvanic corrosion, while the cathodic kinetic process controls the galvanic corrosion rate. It is found that the galvanic effect between Cu and Zn is much less than that between Zn and Fe when ohmically coupled. This is opposite to the theory of galvanic series. Despite possessing the maximum corrosion potential difference as the driving force, the galvanic current of Zn-Cu couple is less than that of Zn-Fe couple with equal area ratio. This drives the intermediate metal (Fe) to act as the main cathode in Cu-Fe-Zn trimetallic couple. Furthermore, it is found that Fe can be transformed into the anode due to the area change of Cu. The electrochemical experimental results are in good agreement with the FEM, suggesting that this method can accurately predict the galvanic corrosion behavior of multielectrode systems.