Need suggestions on prep for powerdercoating

[JeepsAreBuilt]

Ok, I got this old warn belleview winch I am restoring.. I plan to powder coat the parts myself. I have Aluminum parts and a steel drum that I need to PC. I sandblasted all the parts.. my only concern now is the steel drum. It was quite rusty and has pitted in some areas. The drum is not cast steel.. but mild steel. So, after sandblasting(I used silca sand), the rust pits do not look very clean - I'm afraid there is still some rust in there. So.. I am wondering If there is something I can do to treat the metal/rust prior to PC'ng so the rust will not come back. I have in the past blasted cast steel parts and rust would come though the PC

Any Ideas ? My ideas.. treat it with rust mort and then blast again. Soak it in vigner for a while ?

I can get some pics up later if needed

 

[930dreamer]

Look at the post below this one.

 

[LoneGunman]

If you still have rust in the pitting I don't think you were aggressive enough with the blasting, I switched from sand to black beauty or aluminum oxide because of the obvious health reason and the sand was not aggressive enough. I do a lot of powder coating and plating, if there is rust still present I won't coat or plate over it or try to cover it, it needs to be removed.

I'm am surprised you had rust coming through, I would think that the rust would cease to grow once covered in PC due to no air being able to get to it.

 

[JeepsAreBuilt]

If you still have rust in the pitting I don't think you were aggressive enough with the blasting, I switched from sand to black beauty or aluminum oxide because of the obvious health reason and the sand was not aggressive enough. I do a lot of powder coating and plating, if there is rust still present I won't coat or plate over it or try to cover it, it needs to be removed.

I'm am surprised you had rust coming through, I would think that the rust would cease to grow once covered in PC due to no air being able to get to it.

It was a a cast iron differential cover that was brand new.. and it had some nice pores to it.. it had some rust when I got it, so I blasted it lightly and PC'ed it. I dont know how long it was before the rust showed up.. but it did. I have a low end eastwood gun - so my coating was prob not very thick.

For my steel drum - I'm gonna get some pics and see what you think. The rust pits are more like black - after sandblasting it did not turn into the gray texture like the rest of the drum.

 

[JeepsAreBuilt]

Pics:

 

[LoneGunman]

hard to tell from the pic but it looks more like dirt than rust, have you cleaned them yet? If it's a part that I am really worried about, meaning I know it's clean but it's just not looking that way, I'll iron phosphate it.

Have you tried power washing it? When I paint (liquid) machinery I'll powerwash the large pieces. I've never tried Ospho under PC but I don't see why it would be a problem, it's readily available (home depot) maybe buy a quart of Ospho, brush it on a scrap piece of steel, PC it and then check to make sure you have good adherence.

 

[John Timmins]

I suggest you bake and re-clean the parts as many as 3-4 times. Oil and cleaning residues will continue to come out of the metal. If it was my choice I would only use polyester powder.

Many secrets are in the powder coater's back room. In 1992 is started hanging out in a place called Powder House of Daytona and this guy was an early source of custom Harley parts back then. There was no way anybody was going to see the temperature(s) of his ovens of the type of mask off tape he used (easy peel off after baking). So innovative was his techniques, the owner had a powdercoated 2x4, a plastic Mercedes emblem, and I have a blue powdercoated + gold metal flake pretzel in my tool box! Unfortunately that business is gone; he sold it for health reasons, and it went down the tubes after that.

Remember, prepping the parts is just the first step. The powder coater's skills will make or break your project. If you are thinking about filling pitted areas with Devcon or some other composite filler, forget it. The baking will cause "gas out" from the material and the powder will bubble as it cures.

 

[JeepsAreBuilt]

Thanks for the tips. I cleaned the drum real well, pre baked once, and shot it. It turned out good, I am happy with it.

The aluminum parts did have some tiny bubbles.. but the parts were cast and had plenty of imperfections.