Why does the USB cable connector rust not long after use?

A USB cable connector's tendency to rust is directly related to the electroplating layer on the connector. If the plating on the metal surface of the USB connector reaches the standard thickness and quality, it won't easily rust. If the plating is poor, it rusts easily. The quality of the electroplating layer is what determines the metal surface's ability to resist oxidation and rust.

In the industry, a salt spray test is used to grade the plating's ability to resist oxidation and rust. The common grades are: passing an 8-hour salt spray test, a 12-hour salt spray test, a 24-hour salt spray test, and a 48-hour salt spray test. The longer the salt spray test the plating passes, the stronger its ability to resist oxidation and rust, and the less likely it is to rust.