There are many surface treatment methods, and a reasonable choice should be made based on the actual situation. When making a choice, you can consider the following aspects.

1. Forms and degrees of pollutants

For cold-rolled steel plates with more oil stains and less rust on the surface, the focus of surface treatment is to remove oil and grease. It can be degreased and cleaned without rust removal treatment. If the oil stains on the steel plate are mainly oils that can undergo saponification reaction, a cleaning agent mainly composed of strong alkali should be selected to promote saponification reaction and remove them; If the main component of oil pollution is mineral oil that cannot undergo saponification reaction, a surfactant with wetting, dispersing and emulsifying ability should be selected as the cleaning agent to emulsify and disperse it and detach it from the surface of the steel plate.

2. The usage environment of the workpiece

If the workpiece is to be used in harsh natural environments in the future, due to the frequent exposure to temperature fluctuations, strong sunlight, rain, snow, sandstorms, and other natural conditions, the corrosion resistance of the coating is highly required. Therefore, multi-step processes such as cleaning, phosphating, and passivation should be adopted to improve the protective performance of the substrate and enhance the corrosion resistance of the coating; For workpieces used indoors, the pre-treatment requirements are generally lower, and the selected process is also simpler.

3. Coating characteristics

The composition of coatings and their adhesion to substrates vary, resulting in different requirements for pre-treatment. The adhesion of vinyl chloride coatings and organic silicon coatings to substrates such as steel is poor, so strict pre-treatment is necessary, especially oil removal, otherwise the coating is prone to complete detachment. Epoxy resin primer, polyurethane primer, etc. have strong adhesion with steel substrates, so these primers have lower pre-treatment requirements and can even be directly applied to rusted steel substrates.

4. Material of the workpiece

At present, the materials of the coated workpieces are mainly steel, non-ferrous metals, engineering plastics, etc. The content and requirements of pre-treatment vary depending on the material. For example, strong alkaline degreasing solution can be used for degreasing steel materials, while neutral or weak alkaline degreasing solution can only be used for cleaning non-ferrous metals that are not resistant to alkali corrosion. The dirt on the surface of plastics is usually organic substances such as release agents, and dissolving them in organic solvents is often the most effective method. Although different materials undergo chemical treatment, the emphasis also varies. The main purpose of chemical treatment for steel and chemically active non-ferrous metals is to improve corrosion resistance, while the main purpose of chemical treatment for plastics is to improve the adhesion of coatings, so different chemical treatment agents are selected. Chemical protection treatment on steel surfaces usually uses phosphating treatment, anodizing treatment is often performed on aluminum alloy surfaces, and plasma activation treatment or solvent etching treatment is often performed on plastic surfaces.

In addition, factors such as the required service life of the workpiece and coating, the equipment required for the processing technology, and the occupied site area that affect the processing cost also need to be considered.

In short, there are various methods for surface treatment, and the selection should be based on the required coating standard type, as well as the cleanliness and smoothness of the coated workpiece after processing, the type and characteristics of dirt, and the degree of contamination. The effects obtained by different surface treatment methods on the same coated material are different, and attention should be paid to selecting a surface treatment method that can ensure both quality and economic feasibility.