It is well known that during the spraying process of metal powder, the powder coating is transported to the spray gun through air flow after fluidization. The spray gun passes through the high-pressure electrostatic generator, and corona discharge is generated at the electrode needle of the nozzle. The negative charge is generated near the electrode. When the powder is ejected from the gun head, the charge is captured to be charged powder, and it will fly to the grounding worker under the action of air flow, electric field and its gravity The parts are adsorbed on the surface of the profile. Therefore, in the process of spraying, we need to do enough precautions.
1. Coating method of metal powder spraying
In most cases, electrostatic spray gun is used for spraying. Because the product contains metal pigment, the system should be grounded well when spraying with electrostatic gun, and low electrostatic voltage and powder output shall be set to prevent the fire phenomenon during spraying. The effect of forming film has a great relationship with the setting, quality or brand of spray gun. After long-term spraying, a large amount of metal powder may accumulate at the discharge needle of spray gun, and the sprayer should clean the discharge needle regularly.
2. The luster of metal powder coating
In most cases, due to the large error, it is not recommended to use a glossometer to measure the luster of the metal appearance coating, but only visual contrast method is used to determine whether it is consistent with the standard template.
3. The recyclability of metal powder coatings
For powder made by dry mixing method, separation will occur in spraying and recovery process, so there will be some difference in the content of metal pigment between recycled powder and new powder, which may lead to inconsistent appearance of coating and color deviation. This is due to the difference in the properties between metallic pigments and powder particles. Experts suggest that the ratio of recycled powder to new powder is at least 1:4. If the powder coating made by bonding fixation method is relatively fixed in the ratio between metal pigment and powder particle, the recycled powder can be reused completely.
4. The coating of metal powder coating
The advantages of coating on metal powder coating are as follows: enhancing the stone strike resistance of metal powder coating; increasing the aesthetic effect of metal powder coating; thoroughly solving the abradability of metal pigment; and improving the weather resistance of metal powder coating. In order to ensure the appearance effect of the cover, the workpiece which has been sprayed for the first time shall not be polluted. Therefore, it is necessary to have fully automatic spray line and two independent spray rooms for spraying separately. It is recommended that the cover coating should not be applied in general.
5. The abradability of metal pigment
Whether it is made by dry mixing or bonding method, the problem of the abradability of metal pigment can not be solved completely. The only way to solve the abradability is to spray a transparent coating on the metal powder coating.
6. Try to keep the spray conditions stable
The same spraying equipment shall be used with the same parameters as voltage and air pressure; the distance between spray gun and workpiece shall be kept as far as possible, and the stability of film thickness shall be kept as far as possible; the powder coating shall be fully fluidized before spraying; when using recycled powder, the ratio of recovered powder to new powder shall be less than 1:4; the complicated metal powder coating or the workers with deep depression shall be avoided as far as possible Parts; it is recommended that multiple pieces used for assembly should be painted at the same time.
