First of all, surface treatment methods should be classified, which may be divided into coating technology, surface modification technology, composite treatment technology, etc
The surface treatment technology of molds mainly changes the microstructure, chemical composition or stress state of the mold surface through surface coating, surface modification or surface composite treatment technology. There are many surface treatment techniques and methods used on molds, which can mainly be summarized as:
Physical vapor deposition, chemical vapor deposition and coating treatment. According to the principle of surface treatment, it can be further classified into: physical methods, chemical methods and mechanical methods. At present, the main technologies that are widely applied in mold manufacturing are nitriding, carburizing and deposition of hardened films. The following introduces several surface treatment methods that are widely used in automotive stamping dies. I. 

1. Sandblasting
Frosted plastic generally refers to plastic films or sheets. When extruding and forming sheets, the surface of the forming roller has frosted patterns. These frosted patterns naturally form during the cooling process of the plastic. This method is simple and fast, and is especially effective for transparent products
2. Polishing
A processing method that reduces the surface roughness of a workpiece by mechanical, chemical or electrochemical action to obtain a bright and smooth surface. Plastic products are generally polished by rolling up sandpaper, which is usually the first step before spraying!
3. Spraying
Plastic spraying mainly involves applying a layer of plastic paint on metal equipment or plastic products, followed by a drying process. Generally, it is baked for about 10 minutes. Thanks to the advancement of paint, to achieve the same effect, there is no need to stick paper as before. Spray painting can isolate air, and spray paint is an insulator, so it can prevent plastic products from aging and static electricity. Most importantly, it has an appearance effect that plastic products themselves do not have
4. Screen printing
The printing plate is usually square and in the shape of a fine sieve. During printing, the ink on the printing plate leaks from the through holes of the plate to the substrate under the pressure of the squeegee. There are many materials for making screen plates, such as nylon (PA), polyester (CA), silk or metal mesh. With this surface treatment, the color presentation will be very ideal.
5. Pad printing
First, etch the designed pattern onto the printing plate, apply ink to the etched plate, and then transfer most of the ink to the object to be printed through a silicone head.
6. Heat transfer printing
Automobile molds are pre-printed on the surface of the transfer film. Through a single processing (heating and pressurizing) by a heat transfer machine, the exquisite patterns on the transfer film are transferred onto the product surface. After forming, the ink layer integrates with the product surface, presenting a realistic and beautiful appearance and significantly enhancing the product's grade. However, due to the high technical content of this process, many materials need to be imported.
Surface treatment of automotive molds is a key technology for enhancing the wear resistance, corrosion resistance, anti-adhesion and service life of molds, directly affecting the quality of stamping parts and production efficiency. For the high-load and high-wear working conditions of automotive molds (such as body panel molds, hot forming molds, aluminum alloy forming molds, etc.), surface treatment technologies are showing a trend of diversification and refinement.