Generally speaking, there are two interpretations of surface treatment in China, one is the broad sense of surface treatment, the surface treatment agent includes pretreatment, electroplating, coating, chemical oxidation. Thermal spraying and many other physical and chemical methods; The other is narrow surface treatment, which includes only sandblasting, polishing and so on.

The workpiece in the processing, transportation, storage process, often with a surface oxide skin, molding sand, rust welding slag and residual oil, dust and other dirt. To coating can be firmly attached to the surface of the workpiece, it must be cleaned prior to coating on the surface of the workpiece, otherwise, not only affects the binding force of the coating and the metal and the corrosion resistance, but also to the base metal in even with protective coatings are able to make the coating corrosion, spalling, influence the mechanical properties and service life. So the surface treatment before painting is a protective layer of excellent quality, prolong the service life of the product and an important guarantee.

The general surface treatment industry, its development in China is not mature, many gaps in technology, lack of relevant information, the degree has not paid enough attention, which resulted in the surface treatment of China's technology level is low and slow development, related to the lack of talent. The surface treatment is in the substrate surface to form a layer of artificial with the matrix mechanical process, physical and chemical properties of different surface.

The surface treatment is designed to meet the corrosion resistance, wear resistance products, decoration or other special functional requirements. For metal castings, we compare the common methods of surface treatment, mechanical polishing, chemical treatment, surface heat treatment, surface coating Surface treatment is the surface of the workpiece cleaning, cleaning, deburring, to oil, to anodize the skin and so on.

(I) Electroplating

In the electrolyte solution , the workpiece is the cathode , and the surface of the workpiece is made to form a plating layer under the action of the external current , and is called plating . The coating can be a metal , an alloy , a semiconductor or a solid particle containing various kinds , such as copper plating , nickel plating , and the like .

(II) Anodizing

In the electrolyte solution, the workpiece is an anode and the process of forming the surface of the oxide film under the action of external current is called anodizing, such as anodizing of the aluminum alloy.

Iron oxidation of available chemical or electrochemical methods. The chemical method is the workpiece in the oxidation solution, depending on the chemical role in the surface anodizing film is formed, such as steel bluing.