Why can’t copper and aluminum wires be connected together?

The chemical and physical properties of copper and aluminum are very different

So copper and aluminum should not be directly connected. If copper-aluminum connection is unavoidable, copper-aluminum transition clips or copper-aluminum transition joints are required.

The electrochemical properties of copper and aluminum are different

If they are directly connected, once they meet the electrolyte formed by water, carbon dioxide and other impurities, a chemical battery will be formed. This is because aluminum is easy to lose electrons to become a negative electrode, and copper is difficult to lose electrons to become a positive electrode. An electromotive force of 1.69V is formed between, and a small current passes through, which corrodes the aluminum wire, which is the so-called galvanic corrosion. This will cause poor contact between copper and aluminum and increase the contact resistance. When a current passes through, the temperature of the joint will increase, which will further accelerate the corrosion of the joint, increase the contact resistance, and cause a vicious circle until it burns out.

Why can’t copper and aluminum wires be connected together?