To achieve smooth and consistent surface finish, one should have regular maintenance of application equipment and be sufficiently aware of any factorys that could affect the quality of surface ie. pretreatment process, types of spraying head, distance between gun and applied surface, gun speed, gun movement pattern-vertically/horizontally, grounding, optimum air flow and air pressure, KV setting, reclaim-to-virgin ratio, types of powder coatings, chargeability and fluidization of powder coatings, curing temperature and time, dusting from environment and spray booth, and humidity atmosphere.
The spraying of metallic powder is subject to a few variables which will considerably influence quality of finish and may well often be the source for variations of color and surface smoothness. Some of these variables are as follows:
Electrostatic and tribo application equipment exhibit different metallic effects. Automatic lines are preferred to hand guns. Short cutting in the gun could be prevented by using a so-called exterior-charging gun tip, as this type of gun has electrodes which protrude into the cloud. The recommended voltage (KV) for spaying metallic powder coating is in the lower range of say 70 or half of the maximum output and with air pressure of 150 gm per minute.
Sufficient grounding is imperative, possibly an additional ground wire directly connected to the part may be helpful.
Reclaim and virgin powder should be consistently fed into the system.
Gold, Brass and Copper effects need to be cured according to precisely maintained curing schedules. Slight temperature changes might discolor the metallic flakes used.
Application equipment positioning
To achieve an even metallic effect, the distance between spraying gun to the part should be maintained throughout the entire spraying process.
TWO COAT PROCESS
In case the two-coat colors (ie metallic powder coatings with clear or other specialty colors) are required, it is advisable to spray the Base Coat, go though only half the regular curing cycle (underbake is desired) and spray another coat (Top Coat) before finishing up with a full curing cycle.