Connectors use metal plating to protect against external factors such as contamination, diffusion of substrate metal, and contact wear.

There are two types of plating used in connectors:

1. The characteristics of using precious metal coating

To varying degrees, noble metal coatings (eg, gold, palladium, and their alloys) are inherently free from surface films. Interfacial metal contact is relatively simple for these coatings as it only requires movement of the companion of the contact surface upon mating. Usually this is easy to achieve. In order to maintain the stability of the contact interface impedance, the connector design requires attention to maintain the noble metal plating on the contact surface.

2. The characteristics of using ordinary metal coating

Common metal coatings, especially tin or tin alloys, appear to be naturally covered with an oxide film. The effect of tin contact plating is that this layer of oxide is easily destroyed during mating, so that metal contacts are easily established. The requirement of electrical connector design is to ensure that the oxide film is broken when the connector is mated, and that the contact interface is no longer oxidized during the validity period of the electrical connector. Re-oxidation corrosion, in wear corrosion, is the main performance degradation mechanism of tin contact coating. The silver contact coating is best treated as a normal metal coating because the coating is susceptible to corrosion by sulfides and chlorides. Nickel plating is also generally regarded as a common metal due to the formation of valve warps.