PRETREATING
Pretreatment is the basic process before the workpiece gets coated. Remove various stains and impurities (such as lubricating oil, emulsion, grease, rust, oxide skin, welding slag, saline- alkali spots, dust, etc.) from the surface of the workpiece to make it clean and free of stains. The selection of chemical treatment or mechanical processing treatment (such as shot blasting) is based on factors such as material, size, and weight of the workpiece.
The pre-treatment methods vary according to different workpieces. Most pre-treatment includesbasicsteps of degreasing (oil removal), corrosion removal (for metal materials), water rinsing, chemical conversion coating, (pure) water rinsing and drying. Engineers need to design various non-standard pre-treatment steps and parameters according to the customer's needs and the characteristics of the workpiece.
DEGREASING
Degreasing is the basic process before chemical conversion coating. The residual oil stains, rust, oxide skin, etc. on the surface of the workpiece can seriously hinder the growth of chemical conversion coating, and also affect the adhesion, drying performance, decorative performance, and corrosion resistance of the coating layers. Only after thoroughly removing these objects can a high-quality film be formed on the surface of the workpiece, achieving the ideal spraying effect. Degreasing can usually be divided into pre degreasing and main degreasing steps.
WATER RINSING
After degreasing, the surface of the workpiece is prone to adhesion of certain non-ionic surfactants and degreasing agents, which require water rinsing. Water rinsing can be divided into ordinary water rinsing and pure water rinsing, and pure water rinsing is suitable for workpieces with high surface cleanliness requirement.
SILANE TECHNOLOGY
Phosphating has been widely used in the pre-treatment process of painting in the past, but harmful heavy metals such as nickel, zinc, and manganese are produced during the phosphating process, making it difficult to meet environmental requirements and causing serious pollution to the environment. At the same time, it poses a threat to people's health. Therefore, silane treatment technology has gradually replaced phosphating technology. Silane treatment does not produce harmful substances such as nickel, zinc, manganese, etc. It does not contain phosphorus, does not require heating, has fewer treatment steps, can eliminate surface adjustment and passivation processes, and is easy to maintain. It has become a widely recognized and adopted coating technology in the pre-treatment process.
DRYING OF THE CHEMICAL CONVERSION COATING
After the workpiece is coated by silane treatment, it enters oven to dry the chemical coating layer. This step can serve two purposes. On one hand, it prepares for the next process of painting by removing moisture from the coating surface, and on the other hand, it further improves the corrosion resistance of the coating layer after painting.