Powder crawls away
I'm trying to powder coat a fan housing for a late model (72-79) VW Bus.
I cleaned it, blasted it, and coated it with another company's powder. It covered nicely but I didn't like the color (gray) so now I'm trying to coat it with Super Wet Black.
I lightly sandblasted the gray powder coat to rough it up a little, blew the dust off with compressed air, wiped it down with denatured alcohol and a lint free rag, and then blew it off again.
Satisfied with the cleanliness of my part, I applied the super wet black. First I hit the nooks and crannies and then moved on to the large, flat areas.
On one of the flat areas the powder seemed to crawl away and leave an exposed crater. Is this what y'all in the powder coating business call a fisheye? I've sprayed lots of cabinets, etc. with liquid paint (painting contractor, 15 years) so I've heard the word fisheye before. My craters look kinda like fisheyes but it's the crawling powder that has me stumped.
So, I saw it happening but I stuck it in the oven and cured it anyway. I was hoping the craters would magically dissappear in the oven but they didn't.
At this point I figured the problem was caused by dirt or something on the surface. No problem, I'll just sand it with some 400 grit and coat it again.
I also entertained the possibility of moisture coming through the air hose so I drained the compressor, checked the filter, and used a different hose that I knew was dry. I also cleaned the gun and used fresh powder.
When I applied the second coat of black powder,the craters came back in the exact same places!!
I blew the powder off and cleaned the part again.
Same craters, same places.
The first coat of gray powder was perfect.
I'm not exactly sure what the fan housing is made of. It looks like aluminum to me, but I'm no expert.
Ok, I've described the problem as thoroughly as possible.
What am I doing wrong?
Please don't tell me I have to strip the powder coat off.
Thanks.
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