Corrosion is the most complex and destructive one of the three forms. Because the corrosion of color coated plate occurs at the interface between metal and environment (medium) and produces chemical or electrochemical reaction, the study of metal corrosion
protection is its main form. One of the more difficult problems in the study of anti-corrosion of other materials. Corrosion classification of metal materials usually includes the following categories:
(1) According to the corrosive environment: dry corrosion and wet corrosion
(2) According to corrosion mechanism: chemical corrosion, electrochemical corrosion and physical corrosion
(3) According to the types of corrosion forms, pitting corrosion and stress corrosion cracking
(4) Metals according to material: Common and practical metals in "Metal Manual"
(5) According to the scope of application: in fact, it is a special application classified according to the corrosive environment.
The phenomena of metal anticorrosion are mainly points (1) and (2) mentioned above. Dry corrosion at point (1) belongs to chemical mechanism while wet corrosion belongs to electrochemical mechanism. Points (3) to (5) belong to the further classification of points (1) and (2). The anticorrosion mechanism of color coated steel sheet is to isolate the substrate from the corrosive medium by using the coating to prevent the chemical or electrochemical reaction on the surface of the substrate. Therefore, the ultimate anti-corrosion problem we want to study should be attributed to the chemical and electrochemical corrosion on the surface of the coated steel plate substrate.
Based on the above-mentioned mechanism of metal corrosion, people have been looking for effective methods to control metal corrosion. After long-term practice, the following kinds of misapplication are basically formed:
(1) When choosing metal materials, choose atmospheric corrosion resistance as far as possible.
(2) Surface protective coating
(3) Change the composition and add corrosion inhibitor to inhibit the corrosion process.
(4) Anti-rust treatment before packing and keeping dry and clean during storage
(5) In structural design, try to avoid cracks, grooves and other places which are easy to accumulate water and cause corrosion stress fracture.