company news about How much do you know about the pretreatment process of electrostatic powder spraying equipment?

What do you know about the pre-treatment process of electrostatic powder spraying equipment? Listen to the explanation of the powder equipment manufacturer! Five processes let you see through! The surface cleaning step of the workpiece before the powder spraying equipment is processed, so that the surface of the workpiece is clean and then powder spraying: "three-in-one" cleaning → water washing → water washing → chemical conversion (chroming)→ water washing → water washing → drying (60 ~ 85℃).
▲ Powder production line equipment (1) degreasing: It is to remove the oil, grease and other pollutants on the surface of the workpiece before erosion, and get a clean surface. In this process, inhibitors are generally added to avoid oxidation of the clean aluminum surface. The degreasing temperature is generally controlled at 50 ~ 70℃, and the degreasing time is 3 ~ 4min, which is related to the surface state of the workpiece. (2) Washing: In each process of electrostatic spraying line pre-treatment, there is one or two washes to remove the chemical liquid on the surface of the workpiece to prevent cross-contamination between the liquid. The first cleaning after degreasing generally uses tap water or well water, but the last few cleaning needs deionized water to avoid poor adhesion and corrosion problems. The conductivity of the deionized water used cannot exceed 30μS/cm, if exceeded, the salt (calcium ions) in the hard water will deposit on the surface of the workpiece during the drying process to form corrosion points, resulting in bubbles in the coating. The first washing pool has no temperature limit, but the chromium washing process requires that the water temperature does not exceed 50 ° C, and the washing temperature is too high, the chromium film may be washed off. Washing time is generally a few minutes, stirring the workpiece or stirring water with air can improve the washing effect.
(3) Alkali corrosion: there is usually a thin natural oxide layer on the surface of the aluminum in the powder production line, which must be cleaned before chromium, and inhibitors need to be added in this process to prevent the clean aluminum surface from being oxidized. The alkali corrosion temperature should be controlled at 50 ~ 70℃, and the alkali corrosion time should be controlled at 7 ~ 8min. (4) Neutralization: the insoluble pickling residue of the alkali etching stage is removed in the neutralization stage. These residues include metallic or non-metallic oxides (such as magnesium oxides, silicon oxides, etc.), which are insoluble in alkaline solutions and can be removed by nitric or sulfuric acid. Many manufacturers now use neutralizing fluids containing chromate, which can prevent the reoxidation of the aluminum surface. The silicon oxide can be removed by fluoride. The immersion time depends on the condition of the pickling residue, generally ranging from 30s to 5min. Neutralization is usually performed at room temperature. (5) Chemical conversion (chromatization) : For aluminum, chromatization is the most commonly used chemical conversion pretreatment method. The chromium film improves the adhesion between the aluminum metal and the coating, and improves the corrosion resistance of the coating. If the chromified film is too thick, the corrosion resistance is improved, but the powder adhesion becomes worse after the powder spraying equipment is used.