help with pits/craters in rim. PICS!

[Heavykote]

I have a customer rim that had flaking, peeling chrome plating. I got it stripped and now there's all these pits and craters. I went about doing the rim like I normally do and used glass bead media for the chrome. I outgassed at 450 for 30minutes, let it cool a bit then hit it. The rim turned out like this.


In the pics you have the pit areas and the bubbling areas. I sanded down some areas and it's not the media. I did another rim exactly the same, but with no damage and it came out perfect.
Could it be that even with outgassing the pitted areas are still outgassing during curing?
Should I outgass a longer period at a higher temp?
or should I just sand it down and hit it cold?

[Popeye]

Re: help with pits/craters in rim. PICS!

That almost looks like fish eyes, normally caused from silicone found in waxes.
IMHO

[Heavykote]

Re: help with pits/craters in rim. PICS!

Trust me, that baby was completely stripped and I'm mister anal when it comes to clean pieces. You should see how many latex gloves I go through. It's gotta be an outgas problem! I'm gonna hit it cold and see what happens. Anyone with a clue?

[Popeye]

Re: help with pits/craters in rim. PICS!

I just said it looked like fish eyes
You said what you off gassed at but not what you cured at.

[Heavykote]

Re: help with pits/craters in rim. PICS!

I cured it at 385 for 25 minutes. Right now I'm curing it again-COLD. we'll see if the bubble effect happens again. I bet it won't, but I wouldn't put my life on it. By the look of it flowing out, I'm gonna be stripping it again. I hate stripping!
You're always learning in the powdercoating field.

[Popeye]

Re: help with pits/craters in rim. PICS!

If it was an old sand cast it still could be off gassing. A newer style rim like that and with the temps you used.. it shouldn't be off gassing.

I don't mean to be anal about it but if it does it again and in the same areas it almost has to be some type of contamination. Especially since you did another rim, same powder, same temps with good results.

Maybe it had a brake fluid leak, mostly silicone based, aluminum is porous and not very many solvents cuts silicone...
I hope it works out for you!

[Heavykote]

Re: help with pits/craters in rim. PICS!

Thanks! You may have hit on something when you were talking about fluids. I think what happened was the chrome plater uses toxic chemicals to strip metals of plating. Some of the residue was left on the rim and when I got the rim it didn't need to be stripped so I didn't bother. I just bead blasted, out gassed and powdercoated the rim.
So, going through that process probably pretty much burned off the chemicals still left on the rim. I just took the rim out and I didn't see bubbles. So, then I guess I can strip it back down and do my usual process and it should be good.
Other than my attempt at sanding the finish to coat again and it coming out fubared, then I'm good to go.