Why can't aluminum wire and copper wire be connected?

1. The potentials of copper and aluminum are different, and the parts in contact with copper and aluminum will accelerate the oxidation of aluminum wires due to the reaction of the primary battery, and the copper and aluminum joints will have poor contact after a long time. To connect together, copper-aluminum transition clips or transition conduits must be used.

   
   

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2. This is a chemical problem. The chemical properties of metals are relatively vivid and inactive. For example, gold never rusts. This shows that gold is chemically inactive, iron is easy to rust, and iron is more vivid than gold. Putting metals together will speed up the oxidation of vivid metals. Compared with copper, aluminum is more vivid. The connection of the two cables will speed up the oxidation of aluminum (that is, rust), which will affect the use.

3. When the copper and aluminum conductors are directly connected, the contact surface of the two metals can easily form an electrolyte under the action of moisture, carbon dioxide and other impurities in the air, thus forming a galvanic battery with aluminum as the negative electrode and copper as the positive electrode. , galvanic corrosion of aluminum occurs, and the contact resistance of the connection between copper and aluminum is increased.

In addition, because the elastic modulus and thermal expansion coefficient of copper and aluminum are very different, after many hot and cold cycles (power-on and power-off) in operation, a large gap will occur at the contact point, which will affect the contact and increase the increased contact resistance. The increase in contact resistance will cause the temperature to rise during operation. Corrosion and oxidation will intensify under high temperature, and a vicious circle will occur, which will further deteriorate the connection quality, and eventually lead to excessive temperature of the contact point and even smoke, burning and other accidents.