Galvanic corrosion behavior between ADC12 aluminum alloy and copper in 3.5 wt% NaCl solution

Abstract

The galvanic corrosion behavior between ADC12 aluminum alloy and copper was investigated in 3.5 wt% NaCl solution by open circuit potential (OCP), polarization curve, electrochemical impedance spectroscopy (EIS) and galvanic corrosion tests, combined with scanning electron microscope (SEM), optical microscope and X-ray photoelectron spectroscopy (XPS). The OCP test demonstrated that, under coupling condition, it was very necessary to stabilize the OCP for a certain period after disconnection for polarization curve and EIS tests, the OCPs of aluminum alloy and copper was more negative than that before coupling, and the varieties of their OCPs were significantly different from that without coupling. The polarization curve and EIS tests demonstrated that the galvanic effect between them reduced their corrosion in the initial stage (1 h) of galvanic corrosion, and with immersion time prolonged, the corrosion rate of aluminum alloy increased. The galvanic corrosion tests demonstrated that the anode and cathode processes of galvanic corrosion were closer to that of aluminum alloy, and the galvanic current density first decreased and then kept between 45 µA·cm−2 and 50 µA·cm−2 with rising of soaking time. The surface analysis demonstrated that the galvanic effect inhibited the formation of pitting on the surface of aluminum alloy, but promoted the formation of pitting on the surface of copper.