Human sweat is a colorless, transparent or yellowish liquid with a salty weak acidity and has a pH of 5-6. In addition to containing sodium, potassium, calcium, magnesium, but also contains a small amount of urea, lactic acid, citric acid and other organic acids. When sweat comes into contact with the metal, it forms a layer of sweat film on the metal surface, and the sweat film causes electrochemical effects on the metal, corroding the metal.