Metal powder coatings refer to all kinds of powder coatings containing metal pigments (such as copper, gold, silver and aluminium powder, etc.). Because metal powder coating can display a bright and luxurious decorative effect, it is very suitable for indoor and external objects such as furniture, jewelry and automobiles. Dry-Blending is mainly used in the domestic market at present, and Bonding is also used in the international market.

I. Coating Method of Metal Powder Coatings

Friction spraying gun is not suitable for powder coatings. In most cases, electrostatic spraying gun is recommended for semi-coating. Because this type of product contains metal pigments, it is necessary to ensure good grounding of the system when using electrostatic gun in construction, and set a lower electrostatic voltage and powder output to prevent ignition during spraying. The effect of forming film is closely related to the setting, quality or brand of spray gun. After a long time spraying, a large amount of metal powder may accumulate at the discharge needle of the spraying gun, and the cleaner of the air supply system needs the builder to clean the discharge needle regularly.

Purification air supply system

2. Gloss of Metal Powder Coatings

In most cases, because of the large error, we do not recommend using glossometer to measure the gloss of metal surface coating, but only using visual contrast method to judge whether it is consistent with the standard sample.

III. Recyclability of Metal Powder Coatings

For the powder produced by dry mixing method, because of the separation phenomenon in spraying and recycling process, there will be some difference in the content of metal pigments between the recycled powder and the new powder. Automobile coating line may cause the appearance of the coating film to be inconsistent and the phenomenon of color bias. This is due to the difference in properties between metal pigments and powder particles. Experts from China Epoxy Resin Industry Association recommend that the ratio of recycled powder to new powder be at least 1:4. If the powder coatings manufactured by bonding and fixing method are used, the recycled powder can be reused completely because the ratio between metal pigments and powder particles is relatively fixed.

4. Shielding Layer of Metal Powder Coatings

Re-spraying coatings on metal powder coatings has the following advantages: enhancing the stone resistance of metal powder coatings; increasing the aesthetic effect of metal powder coatings; completely solving the scrapability of metal pigments; improving the weatherability of metal powder coatings. In order to ensure the appearance of the covering layer, it is required that the workpiece sprayed for the first time should not be polluted. Therefore, there is a general need for fully automated spraying lines and two separate spraying rooms to be painted separately. It is recommended that the coating should not be sprayed in general. Only when the requirements are very high, such as: high-grade household appliances, automotive wheels and outdoor use (to ensure weather resistance), etc.

5. Scrapability of Metal Pigments

Whether the powder is made by dry mixing method or by bonding and fixing method, the erasability of metal pigments can not be completely solved. The only way to solve the problem of erasability is to spray a transparent coating on the metal powder coating.

6. Ways to Keep the Appearance of Metal Powder Coatings Consistent

1. For the same product, try to use the same batch of metal powder coatings, so as to avoid the problem of difference between batches of powder coatings.

Keep the spraying conditions as stable as possible. Using the same set of spraying equipment, using the same voltage, pressure and other parameters; keeping the distance between the spray gun and the workpiece as constant as possible, keeping the stability of the film thickness as far as possible; ensuring that the powder coating has been fully fluidized before spraying; using recycled powder, should ensure that the ratio of recycled powder to new powder is less than 1:4; avoiding the use of metal powder as far as possible. Paint spraying for workpieces with complex shape or deep depression is recommended. It is suggested that multiple workpieces assembled together should be sprayed simultaneously.