How to prevent corrosion?

Commonly used methods are: 1. Structural change method. For example, making various corrosion-resistant alloys, such as adding chromium and nickel to ordinary steel to make stainless steel. Second, the protective layer method covers the metal surface with a protective layer to isolate the metal products from the surrounding corrosive media, thus preventing corrosion. For example: 1. Coat the steel surface with oil, vaseline, paint, enamel, plastic and other nonmetallic materials. 2. By electroplating, hot plating, spraying and other methods, the steel surface is plated with a layer of metals that are not easy to be corroded, such as zinc, tin, chromium, nickel, etc. These metals usually form a dense oxide film due to oxidation, thus preventing the corrosion of steel by water and air. 3. A fine and stable oxide film is formed on the surface of steel by chemical method. For example, a fine black ferroferric oxide film is formed on the surface of steel parts such as machine parts and guns. Thirdly, the electrochemical protection method uses the principle of galvanic cell to protect metals, and tries to eliminate galvanic cell reactions that cause electrochemical corrosion. Electrochemical protection methods can be divided into anode protection and cathode protection. Cathodic protection method is widely used. 1, sacrificial anode protection method This method is to connect active metals (such as zinc, magnesium and other metals or alloys) to the protected metals. When electrochemical corrosion occurs, the active metal acts as a negative electrode for oxidation reaction, thus reducing or preventing the corrosion of the protected metal. This method is often used to protect steel piles and ship hulls in water, such as steel gates in water. Usually, several zinc blocks are welded on the rudder below the waterline of the hull or near the propeller to prevent the hull from corrosion.