I found sand blasting aluminum prior to powder coating is a big no-no.

[mtumbleson]

Originally Posted by nuttyman

sheeesh! perception is a subjective thing I guess! my wife often tells me that I tend to be crass & insensitive when dealing with others. is this something left over from childhood?! I don't like arguing either.


nutty

It just came across that you were insinuating the bad finish was do to the lack of cleaning prior to shooting, I can assure you wasn't the case.

Originally Posted by mtumbleson

Yes sir I agree, but there is always some finishing needed when parts come off the mill.

Media blasting is always the quickest and easiest to de-burr and prep the surface for powder coating. Problem is it's hard to sell a product with glass media in the finish.

I know all about the machine work involed.... But if you want to smooth it out a little greaseless sand compound works wonders ....

[engineerscott]

I would guess with newly minted hardware that media blasting is not something that you have to do (but it is the easiest and fastest way to dress a part as the original poster stated). However, I can envision situations where you are refinishing/restoring an old aluminimun part where media blasting is almost the only practical way to get a part down to bare metal in preparation for powder coating. I think that mtumbleson has found a valuable insight into the problems with power coating after glass bead blasting aluminimun parts. So, we'd like to find a way to media blast without the issue of media showing up in the power coat finish. Seems there are two ways to attack the problem, i.e. find a way to get the media cleaned out of the pores before pc-ing or find a media to blast with that does not have this problem. If I read the original poster right it sounds like boiling the part in water after blasting might help. This would be difficult on larger parts. Wonder what a hot, high pressure washer would do? I think a better solution would be to use a media that doesn't not have the problem in the first place. I've heard of media blasting with dry ice (frozen C02) pellets. Can't remember what the application was but that would have the advantage that any media that embeds in the pores will turn to gas and evaporate. I have no idea what frozen C02 pellet media would cost, and of course you have to buy the stuff and use it fairly quickly so that's a hassle, but you definitely won't end up with media in your powder coat. Maybe there are other media that would also be better than glass beads, but it would take some experimentation to find out.

[pickleboy]

aluminum shot should do the trick, it comes in very small pellets and is said to feed thru standard blaster guns.

[Popeye]

We powder a fair amount of extruded aluminum as well. Larger parts we blast with aluminum oxide and we see excellent results. It must be specific to glass beads as suggested by Sdold.

[nuttyman]

I always wire brush prior to washing after beading & have never had an issue.


nutty

[sdold]

I wonder if we still get embedded particles when using aluminum oxide, but paint sticks to it OK so we don't notice it?

[seanc]

I've only done this one aluminum piece, but had no trouble with it:



Larger image

After initial cleaning, it was bead blasted, air blown, then powdercoated. The part is rough because it's @40-50 years old, but the PC is smooth and stuck well.

Sean

[engineerscott]

If anyone is interested you can find more info on dry ice pellet blasting here:

http://www.coldjet.com/en/FAQ.html#b

[mtumbleson]

The dry ice sounds interesting, but in my situation would not be cost effective. I will give some of the other ideas a try though….