Pin hole problem

Sir

I am trainee in powder coating dept. We are doing powder coating on bathroom hanger made of mild steel. We first phosphate it then coat powder manually with epoxy powder, then we bake it for 10 min. Our main problem is pin holes come on the component. rejection is about 30 %. Please tell me the solution of this problem

Mr. Singh,

I can't give you the solution, but I can give you the cause, pinholes are caused when two incompatible powders are mixed, or sprayed in close proximity of each other. If the source is airborne contamination, it will happen between the exit end of the paint booth and the entry of the oven. It's a good idea to have this area completely enclosed, If that isn't a possibility, make it taboo for ANYBODY to use spray paints or any type of aerosol anything close to the freshly painted parts. If it's a cross-contamination problem, it could be that the clean-up from whatever was being sprayed previously was not done properly. If the painter uses a powder supply hose for both polyurethane and epoxy paints, the probability of cross-contamination (and pinholes) is high on the suspect list. Now that you know the cause, the solution is to investigate! Good Luck.