Metal by environment of effect, by with chemical or electric chemical reactions by caused of destructive against, called corrosion, almost all of metal products, in must of environment in the, will has several type State of corrosion phenomenon, and drill tail nail is metal products, natural cannot avoid metal corrosion of problem, its using of environment and the time not while, corrosion of phenomenon also has obviously of differences. There are many polluting industries, such as iron and steel, petrochemical, power generation, coupled with recent sharp growth in car and motorcycle, and emissions of gases, the air full of corrosive sulfur and nitrogen compounds in gases and particulates, which is a major cause of metal corrosion.
Surface corrosion in metal processing refers to the use of a variety of methods applying a protective coating, which consists of metal and corrosive environment, to inhibit the corrosion process of producing, or decrease the corrosive medium in contact with metal surfaces, and achieve the purpose of preventing or reducing corrosion. Protective layer should be able to comply with the following requirements: 1. high corrosion resistance, wear resistance, hardness, 2. structure compact, complete, pore small, 3. a base metal with a solid, good adhesion, 4. evenly distributed and have some thickness. Cover is usually divided into two types of metallic and non-metallic coatings, corrosion resistance for metal coating refers to strong metals or alloys susceptible to corrosion in the metal forms a protective coating, this coating and plating. Method of producing metallic coatings and type quite a bit, one of the most common is the electroplating method, followed by the molten metal dip plating method (hot-dip) and chemical surface treatment.
Non-metallic coating is an organic polymer materials, such as paint, and inorganic materials such as ceramic, metal equipment or parts forming a protective layer on the surface, the protective layer of metal can be isolated from environmental media is to prevent metal corrosion due to contact with corrosive media.