Metal coating

Metal coating is applied to the surface of products through methods such as spraying, electroplating, oxidation (treatment), blueing, phosphate treatment (chemical treatment), etc. Metal coating refers to a coating prepared by thermal spraying using metal as the spraying material.

Principles and advantages of metal coatings

During operation, the electrostatic spray gun or spray cup is connected to the negative electrode, and the workpiece is connected to the positive electrode and grounded. Under the high voltage of the high-voltage electrostatic generator, an electrostatic field is formed between the end of the spray gun (or spray plate or spray cup) and the workpiece. The electric field force applied by the coating particles is proportional to the voltage of the electrostatic field and the charge of the coating particles, and inversely proportional to the distance between the spray gun and the workpiece. When the voltage is high enough, an air ionization zone is formed near the spray gun end, and the air is violently ionized and heated, forming a dark red halo around the sharp edge of the spray gun end or needle, which can be seen clearly in the dark. At this point, the air produces a strong corona discharge. The film-forming substances in coatings, namely resins and pigments, are mostly composed of high molecular weight organic compounds, which mostly become conductive dielectrics. Solvent based coatings include organic solvents, cosolvents, curing agents, electrostatic diluents, and other additives. Excluding benzene, xylene, solvent gasoline, etc. These solvent substances are mostly polar substances with low electrical resistivity and certain conductivity, which can improve the charging performance of coatings. The molecular structure of dielectrics can be divided into polar molecules and non-polar molecules. Dielectric materials composed of polar molecules exhibit electrical properties when subjected to an external electric field; Dielectric materials composed of non-polar molecules exhibit polarity under the action of an external electric field, thereby generating affinity for external conductive charges, causing their outer surface to be locally charged in the external electric field. The paint is atomized by the nozzle and sprayed out. The atomized paint particles are charged through contact when passing through the pole needle of the gun muzzle or the spray plate and the edge of the spray cup. When the gas ionization zone is generated by corona discharge, the surface charge density will increase again. Under the action of an electrostatic field, these negatively charged coating particles move towards the surface of the workpiece with conductivity, deposit on the surface of the workpiece, and form a uniform coating film.