Answer: Metal materials are mainly damaged in three forms: fracture, wear and corrosion, among which corrosion is the most complex of the three forms and the most destructive to metals. Because metal corrosion occurs between metals and the environment ( medium) on the same interface, and produce chemical or electrochemical reactions. Therefore, metal anti-corrosion research is a difficult one in other material anti-corrosion research.
Metal anti-corrosion research was formed gradually as a system. It was in the middle of the 18th century. Jiomohnob explained the oxidation of metals in 1748. Kayle described the passivation in nitric acid in 1790. Phenomenon. De la Rive proposed the concept of a micro-battery for metal corrosion in 1830. Faraday proposed the laws of electrolysis in 1833-1834. These theories have greatly promoted the further development of corrosion science.
Metal anti-corrosion as an independent science began in the early and middle of the 20th century. During this period, the world experienced the First World War and the Second World War. Weapons in the war needed ocean transportation and storage. In order to prevent rust, the United Kingdom established in 1943 The packaging standard (BS1133) was released in 1999. During the Second World War, the United States had to solve the corrosion problem of weapons transported to high-temperature and humid areas in Southeast Asia. It also formulated P series standards for anti-rust materials, which greatly promoted metal anti-rust technology. After the war, these technologies were gradually transferred from military use to civilian use, and a research system was basically formed after the 1950s.
The corrosion classification of metal materials usually has the following types:
(1) According to the corrosion environment: dry corrosion, wet corrosion;
(2) According to the corrosion mechanism: chemical corrosion, electrochemical corrosion, physical corrosion;
(3) According to the type of corrosion form: pitting corrosion, stress corrosion cracking;
(4) Metal materials: common and practical metals in the "Metal Handbook".
(5) According to the scope of application: In fact, it is a special application classified according to the corrosive environment.
The anti-corrosion phenomenon of metal. It is mainly the points (1) and (2) mentioned above. The dry corrosion of point (1) belongs to the chemical mechanism and the wet corrosion belongs to the electrochemical mechanism. The points (3) to (5) ) points, all belong to the further classification of (1) and (2). The anti-corrosion mechanism of color-coated steel plates is to use the coating to separate the substrate from the corrosion medium. A chemical or electrochemical reaction occurs on the surface of the substrate. Therefore, the anti-corrosion problem we finally studied should be classified as chemical corrosion and telephone corrosion on the surface of the coated steel plate substrate.
Based on the above metal corrosion mechanism, people have been looking for effective metal corrosion control methods. After long-term practice, the following measures have basically been formed;
(1) When choosing metal materials, choose those that are resistant to atmospheric corrosion as much as possible;
(2) When designing the structure, try to avoid gaps, pits and other places that are prone to water accumulation and cause corrosion and should be fractured;
(3) Change the composition and add corrosion inhibitors to inhibit the corrosion process;
(4) Anti-rust treatment before packaging. Keep dry and clean during storage:
(5) Adopt surface protective covering coating;
