In this study, the galvanic corrosion behavior of the tinned Cu terminal coupled with Al–Mg–Si alloy was analyzed. When the Al, Sn and Cu were exposed to the electrolyte, tri–metallic galvanic corrosion occurred between them. The polarization curves show that the corrosion potential increases in the order: Al < Sn < Cu. Therefore, when the tinned Cu is coupled with Al–Mg–Si alloy, Al alloy with the lowest corrosion potential becomes the anode, while Cu with the highest corrosion potential becomes the cathode. Sn, which has an intermediate potential, becomes either anode or cathode. Since all three metals have steeper cathodic Tafel slopes than an anodic Tafel slopes, the galvanic corrosion rate is determined by the area of cathode. Therefore, the area ratio of Sn and Cu to Al alloy is the main factor affecting the total corrosion rate of the Al–tinned Cu couple. The ZRA results and the Tafel relationship show that the total galvanic corrosion rate increases as the area ratio of Sn plating decreases. Consequently, to prevent failure by corrosion of the connection of the Al body and the tinned Cu terminal, their joining should be performed to minimize damage to the Sn plating.
Recently, as environmental regulations have become more severe, the demand for electric vehicles (EV) has increased In the EV system,1 previously mechanically controlled parts become electrically operated.2,3 Accordingly, stable electrical connection between the parts using a wiring harness is becoming more important for reliable operation of the EV.4 Tinned Cu, whose resistance to both corrosion and wear is excellent, is widely used for wire and terminal for wiring harnesses. Tinned Cu is also used in braided wire to shield against electromagnetic interference from high-voltage cables in the EV. These wiring harnesses and braided wires are grounded to the vehicle body for stable current flow and potential regulation. However, there is a case in which the joint between the body and the electric terminals failed due to corrosion.5,6 Additionally, corrosion of the joint increases the electrical resistance by the corrosion products, which reduces the voltage stability of the electrical parts. Therefore, study to prevent corrosion of the ground contact part in EV is required.