Powder Coating Issue - Vintage Mustang Forums
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post #1 of 6 (permalink) Old 05-08-2019, 09:41 AM Thread Starter
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Powder Coating Issue

I powder coated a new differential cover and it came out with sort of a grained appearance. The color was semigloss black, air pressure was at 8 PSI. The cover is new and was bead blasted, cleaned with acetone then pre baked at 400º for 30 minutes prior to coating. Anyone have any ideas?

John

The Fauxstang. Dynacorn 67 fastback. Dart SHP 363, Close ratio Magnum 6 speed, 3.70 Eaton Truetrac in a fabricated full floater 9", SorT coil over suspension. Still in pieces.
'14 SHO with most all the bells and whistles. Stock for now.
F-150 SCab daily driver
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post #2 of 6 (permalink) Old 05-08-2019, 01:07 PM
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By grained do you mean flecks or small chunks of power baked into an otherwise smooth finish? If so I had/have the same issue an when Techshop was around one of the gals showed me some tips...

1) How fresh is the powder? Old powder or power exposed to moisture or heat will clump and do that.

2) How is your application technique? They tell me keep the cloud going. Don't spray it like you do paint by starting and stopping the trigger. I had the issue with both my Eastwood gun and the pro level gun at Techshop. By doing that I got better results.

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post #3 of 6 (permalink) Old 05-08-2019, 02:21 PM Thread Starter
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When I spray, I use a sort of circular motion with the gun. It seems to keep the powder agitated and I get more powder out of the tip. I keep my powders enclosed in double plastic containers to try and avoid moisture.

I sprayed another piece at the same time as the differential cover, and it came out perfect. The Diff cover however had a grainy appearance, similar to the grain on the inside of the door on a gen 1 Mustang, but not quite as pronounced. I didn't use a primer, could possibly be it needed more thickness to smooth out?

John

The Fauxstang. Dynacorn 67 fastback. Dart SHP 363, Close ratio Magnum 6 speed, 3.70 Eaton Truetrac in a fabricated full floater 9", SorT coil over suspension. Still in pieces.
'14 SHO with most all the bells and whistles. Stock for now.
F-150 SCab daily driver
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post #4 of 6 (permalink) Old 05-08-2019, 04:11 PM
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Good thing it goes under your car and nobody will really ever see it.

Sorry...I've obsessed over stuff that nobody will ever see too, so just giving you some $h1t
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Dan
Chapel Hill, NC
***PM me if you're close by and can lend a hand with my 65 Fastback project***
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post #5 of 6 (permalink) Old 05-10-2019, 11:06 AM
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Quote:
Originally Posted by j persons View Post
I didn't use a primer, could possibly be it needed more thickness to smooth out?
Could be. What you describe is different than what I experience. Could be contamination on the substrate. The only priming I'm familiar with is using an adhesion promoter (basically liquid iron oxide) though I've seen primers for sale. It's cheap, only about $10 a pound.

67 Hardtop, brought it back to a driver
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post #6 of 6 (permalink) Old 05-10-2019, 02:52 PM
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contamination- whether its lint from a rag, metal filings, sand from sandblasting or even another color/powder left in the gun
old or clumped powder
excessive powder on part (gives a surface of the moon like appearance)
moisture in airline
incomplete cure

Note: high temp powders will contaminate the gun and do a funny looking coating if used with regular powder- so super good cleanup is needed if u use these kinds

Post a pic- (I know its gonna be hard to see) but maybe we can tell from that

If its lightly coated- you can reshoot and rebake- (if your gun doesn't like second coats- heat part up to about 300- shoot it hot then rebake to cure it
If its heavy coated- use solvent or torch to eat the powder off then reblast then reshoot (you could sand it or try to sandblast the powder but its labor intensive to say the least
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