There are many surface treatment methods, and a reasonable choice should be made according to the actual situation. The following aspects can be considered when choosing.
1. The form of pollutants and the degree of pollution
For example, for cold-rolled steel sheets with a lot of oil on the surface and less rust, the focus of surface treatment is to remove grease. Can be degreased and cleaned without deGraduation. If the oil stain on the steel plate is mainly grease that can undergo saponification reaction, a cleaning agent with strong alkali as the main component should be selected to promote it to undergo saponification reaction and be removed; if the main component of oil stain is mineral oil that cannot undergo saponification reaction, The surfactant with wetting, dispersing and emulsifying ability should be selected as the cleaning agent, so that it can be emulsified, dispersed and detached from the surface of the steel plate.
2. The use environment of the workpiece
If the workpiece will be used in the harsh natural environment in the future, due to the influence of natural conditions such as drastic temperature changes, strong sunlight, rain, snow, wind and sand attacks, the corrosion resistance of the coating film is very high, it should be used Cleaning, phosphating, passivation and other multi-step processes can improve the protective performance of the substrate and improve the corrosion resistance of the coating; while for workpieces used indoors, the requirements for pretreatment are generally lower, and the selected process is also simpler.
3. Coating properties
The composition of the coating is different, the bonding force with the substrate is different, and the requirements for pretreatment are also different. For example, perchlorethylene coatings and silicone coatings have poor adhesion to steel and other substrates, so stricter pretreatment is required, especially effective degreasing, otherwise the coating will easily fall off. However, epoxy resin primers, polyurethane primers, etc. have a strong binding force with steel substrates, so these primers have lower requirements for pretreatment, and can even be directly painted on rusty steel substrates.
4. The material of the workpiece
At present, the materials of the coated workpieces are mainly steel, non-ferrous metals, engineering plastics, etc. Different materials have different pretreatment contents and requirements. For example, strong alkaline degreasing liquid can be used for degreasing steel materials, while non-ferrous metals are not resistant to alkali corrosion, so they can only be cleaned with neutral or weak alkaline degreasing liquid. The dirt on the surface is usually an organic substance such as a release agent, and dissolving it with an organic solvent is often an effective method. Although different materials are chemically treated, the emphasis is also different. The main purpose of steel and non-ferrous metals with active chemical properties is to improve corrosion resistance, while the purpose of chemical treatment of plastics is mainly to improve the adhesion of the coating film, so the chemical treatment agents used are completely different. Phosphating treatment is usually used for chemical protection treatment on steel surface, anodic oxidation treatment is often used on aluminum alloy surface, and plasma activation treatment or solvent etching treatment is often used on plastic surface.
In addition, factors that affect the processing cost, such as the required service life of the workpiece and the coating, the equipment required for the processing process, and the occupied site area, need to be considered.
In short, there are various methods of surface treatment, which should be selected according to the type of coating standard to be obtained, and at the same time, should be selected according to the cleanliness and smoothness of the coated workpiece after processing, the type and characteristics of dirt, and the degree of pollution. The effect obtained by different surface treatment methods for the same coated object is different. Care should be taken to select a surface treatment method that can not only guarantee quality but also be economical and feasible.
