Galvanic Corrosion of Tinned Copper Coupled with Aluminum Alloy in Electric Vehicle

This study analyzed the galvanic corrosion behavior of a tinned Cu terminal coupled with an Al-Mg-Si alloy. When the Al alloy and tinned Cu were electrically connected and exposed to an electrolyte, tri-metallic galvanic corrosion occurred between the Al alloy, the Sn plating, and the Cu base metal. Results from potentiodynamic and zero resistance ammeter tests indicate that the total galvanic corrosion rate increases as the area ratio of Sn plating to the Cu base metal decreases. Furthermore, the Sn, which has an intermediate potential, may function as an anode or a cathode. While most of the Sn plating was protected by the Al alloy, corrosion of the Sn plating was observed at the boundary between the Sn plating and the Cu base metal. Thus, the exposed Cu area and galvanic corrosion of the Al-tinned Cu couple increase over time. Consequently, to prevent failure due to corrosion at the connection of the Al body and the tinned Cu terminal, the exposed Cu area and damage to the Sn plating of the tinned Cu terminal should be minimized.