Where the
world gathers for metal finishing
Q&As since 1989


-----

ESD powder coating

2000

Great site except I couldn't find anything about using corona guns with all Nordson equip. and every time we try to powder coat esd. paint it is a new nightmare all over again? most of our trouble is the finish just is way too difficult to make look presentable . second coating usually looks worse than the first paint: is either too light or starts to overbuild causing what I would call pop marks . any help would be greatly appreciated .

thanks
LOU

Lou costanza
- Kenilworth, New Jersey

The "pop marks" sound like what is known as Back-Ionization. This is caused by poor dissipation of the excess electrical charge from the piece being coated. A grounding issue of the part is typically the problem. I use multiple grounds on typical small parts, but on a larger, Flat metal piece, the build-up is quite a bit more substantial and will require a different approach. I have learned from experience, that I can actually use my bare hand and hold the hanging hook/wire, and virtually eliminate all back-ionization. Of course you will have a pretty heavy coverage on your hand and arm also. This increases waste, and should be calculated into your cost of coating, and the amount of powder purchased for the job.

Scott Terrell
specialty powder shop - Garland, Texas
March 14, 2009