Methods for preventing metal corrosion

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Metal materials are the most widely used engineering materials in modern society, playing a very important role in human civilization and development. Metal materials are not only used in industrial and agricultural production as well as in scientific research; they can also be seen everywhere in daily life, with metal materials being utilized at all times. However, metal materials tend to react with the surrounding medium, leading to metal corrosion; once corroded, their properties **decrease**. If the metal components of a device corrode, it will become unable to function, causing economic and other losses to people. Therefore, metal corrosion prevention is very important. There are many methods to prevent metal corrosion, which can be categorized as follows: First, during the manufacturing of metal parts, corrosion-resistant materials that do not react easily with the surrounding environment are added. For example, metals such as chromium and nickel-titanium do not oxidize easily in air; they can form dense coating films that resist corrosion from acids, bases, salts, etc. When added to iron or copper, they enable the creation of metal products with excellent corrosion resistance. Metal powder metallurgy facilitates flexible mixing of various metal elements; by using metal powders with different properties, metal parts with excellent corrosion resistance can be produced. Metal materials such as iron-carbon alloys can also be protected from corrosion by using heat treatment methods. II. Use coating methods for corrosion prevention. Coating methods include three main categories: coating and spraying, plating, and chemical conversion coatings. A protective layer is created on the metal surface to prevent contact between the metal and corrosive agents, thereby reducing corrosion. Coating involves applying organic and inorganic compounds to the surface of metals; common methods include painting and plastic coating. Spraying is a coating technique in which, using a spray gun or disc atomizer, substances are dispersed into uniform and fine droplets under the action of pressure or centrifugal force and applied to the surface of the object to be coated. The main types of spraying include arc spraying, plasma spraying, electrostatic spraying, and manual spraying. Metal plating is a process in which metal powder is used to form a coating on the surface of a workpiece; it includes methods such as electroplating, hot-dip plating, spray plating, immersion plating, chemical plating, mechanical plating, and vacuum plating. Chemical conversion coatings are formed on metal surfaces through chemical or electrochemical methods to create stable compound layers; depending on the medium used in the coating process, these coatings can be classified as oxide coatings, phosphate coatings, chromate coatings, etc. Based on the materials that make up the protective layer of a coating, they can be classified as: (1) Non-metallic protective layers: such as paint, plastics, fiberglass, rubber, asphalt, enamel, concrete, faience, rust preventive oils, etc. (2) Metal protective layer: A metal or alloy is plated on the metal surface as a protective layer to slow down the rate of corrosion. Metals used as protective layers typically include zinc, tin, aluminum, nickel, chromium, copper, cadmium, titanium, lead, gold, silver, palladium, rhodium, and various alloys. III. Deal with corrosive media. Handling corrosive media involves altering their properties, reducing or eliminating harmful components in them in order to prevent corrosion. This method can only be used when there is a limited number of corrosive agents; it certainly cannot be applied to the atmosphere that fills a space. The treatment of corrosive media is generally divided into the following two categories. One category is to remove harmful components from the medium in order to improve its properties. For example, using a protective gas in heat treatment furnaces to prevent oxidation, adding lime to acidic soil for neutralization in order to prevent soil corrosion, and so on. Another approach is to add corrosion inhibitors to the corrosive medium. Adding a small amount of corrosion inhibitor to the corrosive medium can **reduce** the rate of metal corrosion; such substances are known as corrosion inhibitors or anti-corrosion agents. For example, certain amounts of caustic soda or lime are added to tap water systems to remove excess carbon monoxide from the water and prevent pipe corrosion; corrosion inhibitors are added to steel pickling solutions to avoid over-pickling and hydrogen embrittlement. IV. Electrochemical protection: A protection method that uses direct current to change the potential of the metal being protected, thereby slowing down or stopping corrosion, is called electrochemical protection. The main types of such protection methods are external power cathodic protection, protector-based protection, and anodic protection.