Self-deposition coating and self-deposition coating are newly developed coating products and coating processes. They are dipping coating techniques similar to electrophoretic coating. The tank solution is composed of polymer emulsion containing pigment (filler), acid (HF) and Oxidizing agent (H 2 O 2 or dichromate) composition. When the metal piece is immersed in the bath, the surface is etched by acid, and multivalent metal ions are generated at the interface, which makes the polymer micelles lose stability and deposit on the metal surface. Due to the special film-forming process of self-coating coatings, compared with electrophoretic coatings, its coating process has the following characteristics:
(1) Energy saving. Autophoretic deposition is a chemical process that does not consume electricity, and saves about 50% of the energy .
(2) High protection performance. In the autophoretic deposition process, the chemical conversion treatment and the coating film deposition are carried out , the metal surface is always in an activated state, the coating film has strong adhesion, and the salt spray resistance performance is equivalent to that of the cathodic electrophoretic coating.
(3) Self-coating eliminates the phosphating process. The entire painting process is shortened, the investment in painting equipment is reduced by 30-60%, and the floor area is reduced by 20-50%.
(4) The autophoretic deposition time is generally 1~2min, which has the same coating efficiency as electrophoretic coating; the solid content of the bath solution is 5%~10%, and the wet film still has high permeability after the paint piece is taken out of the bath solution And reactivity , the surface adhesion bath can continue to undergo chemical action and deposit, only a small part , the utilization rate of paint is better than that of electrophoretic paint, and ultrafiltration recovery equipment is not required.
(5) Self-coating does not have the problem of throwing power. It can cover any surface with a complex shape with a very uniform coating film, and the thickness error is not more than ±1.3μm, which is better than electrophoretic coating and has better decorative appearance. Even at the corners, the coating film has the same deposition ability and better protection ability.
(6) The coating is acid and alkali resistant after curing. Therefore, it is not necessary to remove the coating film on the hanger, reducing the cleaning workload .
(7) The paint does not contain any volatile organic solvents. It fundamentally eliminates the pollution .
(8) Water-soluble additives such as surfactants will not deposit together with film-forming substances, which fundamentally solves the problem of poor water resistance of latex coatings.
However, self-deposition coatings, like electrophoretic coatings, also have storage stability problems. Especially the continuous accumulation of dissolved metal ions in the bath is very unfavorable for the stability of the bath. Considering the economy, it is only practical to update the bath solution more than 20 times, and the update rate is more than 1 week to more than half a year.
