Q: I have recently been experiencing a crater problem on all powders I try. So far, I have changed the three filters, one prior to the dryer and two after. The compressor, air dryer, and filters are all new, installed three years ago and have be maintained according to the manufacturer’s directions.
I tried eight different polyester powders, and I only used epoxy primer and polyester topcoats from a local supplier for the last five years. What I noticed is that the craters/fisheyes are mostly on vertical surfaces; the sides and bottom are not affected as much.
I tried to use a different compressor and also powder gun and three different ovens, which I have a few meters apart, with all same results. I removed any liquid paint and closed everything in a room. I cleaned the powder coating area, dismantled the powder gun, and changed the powder hose from the hopper to the gun. If I powder coat on a hot substrate, the craters don’t appear.
A: Wow, this is perplexing, indeed. Your approaches thus far are all very logical. Compressed air filters, alternate ovens, alternate powders – all wise variables to investigate.
Have you tried different people? Crazy as it may seem, craters can occur from personal care products. Sometimes a hand lotion or antiperspirant or even a cologne can cause craters.
I have also witnessed terrible cratering from contaminated ambient air. A guy in California would get craters in his powder when his neighbor would spray silicone coatings next door. The overspray would drift into his finishing area and create craters in his powder coating.
Another thought: Are your powder coating packages ever left open to the ambient air? Is your spray area enclosed or open to the surrounding area?
Reader response: I may not have explained well. The craters are dense on horizontal surfaces. On the sides and bottom, it’s hard to notice any.
I achieved very good results without the deodorant I have been using for years now. Most probably, when I am pointing the gun downward, my arm is extended and the deodorant vapors cause craters.