Assessment of the galvanic corrosion of bi‐metallic couple 7075‐T6‐aluminum alloy/microalloyed dual‐phase steel

The corrosion behavior of a galvanic coupling consisting of a 7075‐T6‐aluminum alloy and a low‐carbon low‐manganese microalloyed dual‐phase steel was studied in a 3% NaCl aqueous solution at room temperature. Corrosion behavior of the individual materials was assessed from potentiodynamic polarization and electrochemical impedance spectroscopy measurements conducted on the individual couple components. The corrosion rate of the individual samples was found to be seven times larger on the microalloyed steel than on the aluminum alloy. From a comparison of corrosion current densities, the galvanic couple was found to sustain a nonsignificant galvanic effect—the latter in contrast to what may be determined considering differences in their respective corrosion potentials. According to the applied mixed‐potential theory and the zero‐resistance‐ammeter measurements performed directly on the galvanic couple, the aluminum‐alloy acted as the anodic member of the galvanic couple. Such behavior was justified by kinetic parameters rather than thermodynamic ones, considering the favorable rate of the oxygen reduction reaction on the microalloyed steel surface.