Need help - tips for prepping aluminum for powder coating?

[strangersinspace]

I have a chassis that I'll be soon taking to get powder coated, and I tried using a dremel with a wire brush attachment to sort of smooth out certain areas where the chassis was gouged or scratched fairly deeply. Of course I'm not completely smoothing it out, but just making it a bit less obvious by dulling down those tiny sharp edges and valleys. In doing this, it has a similar affect to polishing the surface where I'm working on it - it shines up a bit where I'm brushing on it. I'm hoping this doesn't backfire on me when I get it powder coated by creating an uneven result.

Does this sort of raw/dull vs. brushed/shined surface wind up showing through after powder coating? Am I better off to just completely leave the scratches alone OR just polish the whole chassis evenly? For obvious reasons, I'd rather not brush/polish the whole thing unless it really makes a difference after getting it powder coated.

Any other general advice on the subject is welcome.

Note: I've read the thread where JB weld is discussed, and I'm not looking for that level of perfection where I want to actually use filler material. I just want to use a dremel or whatever and at least get an "even" final result on the powder coat.

Thanks in advance.

[scr8p]

you don't need to polish the chassis for powder coat.

when i redo tubs, i usually rip into them with 80 grit on a da to feather the scratches out. if they all come out, i'll work my way down to 320 or 400, and go right into paint. if they don't come out, i'll shoot some primer over the 80 grit, then block wet sand with 400, then go into paint. as long as all of the scratches came out.

now, that's how i do it for spraying "paint". if you final sand with 180-220 grit or so, that should be fine for powder coat.

[strangersinspace]

Thanks for the quick response.... What is the significance of "DA" sandpaper? Is that a particular type of paper, or a special tool?

I basically have a little handheld block the size of a piece of soap that I can fix my sandpaper to. Would that be sufficient in your opinion?

Also, when you wet sand, how exactly does that work? I've never done that.

Sorry for sounding like a noob

[RedScampi]

DA is dual action or double action. It refers to an oscillating electric or air driven sander.
Wet sanding is done with special wet or dry sandpaper, you can get it at the local hardware store. Using water helps clear the sandpaper so it doesn't wear out so fast.

[jwscab]

everything as said above. Also, if the powercoat isn't a clear pigment, then the finish really isn't critical. I would just hit it with your sanding block with some wet/dry paper, 320 or 400 for a quick overall finish, and then clean it up and send it out to get powdered.

the powder has a reasonable thickness to it, so it will sort if fill in fine scratches.

if it's a clear pigment that you are planning, then I would use some scotchbrite and try and put a nice even finish on it, using uniform strokes, and only going in one direction so it looks brushed.

[LTO_Dave]

It depends on the color and texture of powder being used. If the scratches are somewhat deep, they may show through with certain thin powders that are applied in one coat.

If you're using a wrinkle, hammertone, or textured powder, they hide almost all small imperfections.

Also, the tub will have to be completely bare if you want the powder to adhere like it's supposed to. I've tried to powder a few things without completely stripping the anodizing and the powder did not stick to some areas and was blotchy in others.

And never use JB Weld or any other fillers on something you're having coated. It will not stand up to the 400+ degrees required to cure the powder.

[scr8p]

eastwood sells a putty for fixing imperfections prior to powder coating. it's supposed to withstand the high temps, and the powder is supposed to stick to it.

[strangersinspace]

eastwood sells a putty for fixing imperfections prior to powder coating. it's supposed to withstand the high temps, and the powder is supposed to stick to it.

Another thread recommends this:

http://www.amazon.com/Permatex-26346-Temperature-Repair-Compound/dp/B000ALBZMG

I'm going to see how well I can sand out the imperfections, and if necessary, I might try a small amount of that filler.

[treehugger]

i used that putty on my first run and the guy said when they media blast the pan it will come out also the alloy expands faster than the putty so there is a chance it will pop out or show through the final finish also i rubbed down all my square edges just enough so the PC wont thin on the sharpper edges .

Paul

[ChicagoRC10T]

We do a lot of powdercoating at work. We have excessively high cosmetic and quality standards, but just as a reference point, if you are using a smooth powdercoat, pretty much anything that can be felt by a fingernail will show though in the right light. It all depends on how picky you are.

We've tried powdercoating directly over black anodize and had mixed results. Some parts would come out ok, others had what appeared to be outgassing bubbles. This happened even in milled parts that we pre-baked. I think the final verdict was that the sealing process used can cause problems. I would talk with your powder coater about what they would recommend for the powder you chose and the condition of your chassis parts. As said above, they can probably do media blasting for you, which will save you some time and elbow grease.