What am I doing wrong?

[jpmassey]

I need some help, this is driving me nuts.

I am powder coating new sheetmetal and I can't get a chean finish. 99% of the surface looks great, and then there is a few blotches of bubbles. I am using caswell's super wet black.

My process:

-Sand with 80 grit (not removing the scale, just smoothing it out).
-Soak in acetone for a couple minutes, lightly wipe down with a soaked towel.
-Outgas for 20-30 mintues @ 450*
-Cool to under 200*
-Soak in iron phosphate for a few minutes. (Preheated to ~90*)
-Soak in distilled water for a few minutes
-Hang up
-Dry in oven
-Shoot at about 200*
-Heat up for about 10 mintues (monitor temp with gun)
-Cure at ~400* for 10 minutes
-Cool in oven for another 10 minutes

I use latex gloves for touching.

Whats wrong!!! I have to do alot of these by the end of the week.

Thanks for any help

[jpmassey]

[baz]

Originally Posted by jpmassey

I need some help, this is driving me nuts.

I am powder coating new sheetmetal and I can't get a chean finish. 99% of the surface looks great, and then there is a few blotches of bubbles. I am using caswell's super wet black.

My process:

-Sand with 80 grit (not removing the scale, just smoothing it out).
-Soak in acetone for a couple minutes, lightly wipe down with a soaked towel.
-Outgas for 20-30 mintues @ 450*
-Cool to under 200*
-Soak in iron phosphate for a few minutes. (Preheated to ~90*)
-Soak in distilled water for a few minutes
-Hang up
-Dry in oven
-Shoot at about 200*
-Heat up for about 10 mintues (monitor temp with gun)
-Cure at ~400* for 10 minutes
-Cool in oven for another 10 minutes

I use latex gloves for touching.

Whats wrong!!! I have to do alot of these by the end of the week.

Thanks for any help

out gassing is usually not needed for steel, aluminium is a porous material thet s why it needs to outgas .
cleaning with acetone is ok but the towell could be a problem , it can leave small lint particles on the metal.
contaminated powder could be a problem
moisture in the air line or oil in the air line is a major source of problem
dust in the air or on you or your clothes could also be a source of problem
if you are sure they are bubbles and not dust i would bet on moisture or oil in the line

[jpmassey]

I am using a Motorgaurd air filter, and a coiled copper air cooler. I never have used oil in the lines. I figured the phosphate and water wash would take care of any towel dust particles. I have seen a couple feathers here and there, but they are around sharp edges, etc, not in the middle of a flat spot.

I'll use a different can of powder next batch.

I may be only shooting textered powder if this keeps up.

[Banditperformance]

Try doing one without Phosphate or rinse steps. I rarely phosphate hre. But then most my work doesnt call for it.

[Harleydad]

After the Acetone blow the part off with clean dry air. After the water rinse blow off with clean dry air and run small propane torch over the part to help remove any rag lint or dust bunnies still remaining. Lint free rags (microfiber) may also help. I think I'm with bandit on the contaminated air.

[corecoatings]

I would say to sand blast it back down where it is bubbling, feather it back with a dA or hand sand it, and re coat the virgin metal? I have done it and you can get away with it if you make sure you get your temp up and make the powder flow.

[jpmassey]

I used a different powder can, same result.

I'm going into damage control mode, I'm going to try the speckled black. Probably can't see the small imprevections then.

I had problems with the gun charging last night. I had to turn if off and on several times. Wasted a TON of powder.

[baz]

Originally Posted by jpmassey

I am using a Motorgaurd air filter, and a coiled copper air cooler. I never have used oil in the lines. I figured the phosphate and water wash would take care of any towel dust particles. I have seen a couple feathers here and there, but they are around sharp edges, etc, not in the middle of a flat spot.

I'll use a different can of powder next batch.

I may be only shooting textered powder if this keeps up.

oil could be coming from the compressor. try blowing air on a white piece of paper for a while and check if it gets wet or moist or if it has some oily spots on it .you can add another filter just before the gun to help .
using texture powder will only hide the problem . better to spend alittle tim to find and fix the problem then all your jobs will be better looking

[chromo]

I agree with BAZ. "better to spend alittle time to find and fix the problem then all your jobs will be better looking"

"I'm going into damage control mode, I'm going to try the speckled black. Probably can't see the small imprevections then."

If you gotta get this job done and you can do that perhaps you'll be ok, but it's the chicken SSTT way out maybe. If you take that approach for all your work though you will never be a PRO. When you have a problem you must track it down and kill it! Fix it now, if you don't then it will haunt you for ever.

Happy Halloween