Ways to remove heavy pitting from aluminum
 

Long story short I took my TE's to get media blasted. I found a guy who used a soda based media so I took him one wheel to try it out. Came out great, no pitting and was super smooth and easy to polish.

Guy turned out to be a douche and tried to charge me triple when I brought the other wheels back so I went somewhere else. The guy I found used a silica based media and he assured me it would be just as smooth as the soda based.

Needless to say it wasn't and now I have heavy pitting in my wheels. I tried sanding with 400, 220, 150 and lastly a 80 grit paper which finally got it smooth again.

My question is does anyone have any suggestions on getting the pitting out a little easier? I was planning on trying a steel wool pad with some rubbing compound.

Anyone else have any suggestions. Appreciate it.

Re: Ways to remove heavy pitting from aluminum
 

Media blasting alloys ruins the structural rigidity, bud. Alloy wheels are 1/3 of the density of steel, hence why they're typically chemically stripped. To be honest, I wouldn't even put them on a car if there is visible damage.

Re: Ways to remove heavy pitting from aluminum
 

It sounds as though you've compromised the strength of your wheels! They may be ruined.

Sanding with 80 grit?!? :scared:

Post up some pictures. I work very closely with a wheel repair specialist who can have a look.

Re: Ways to remove heavy pitting from aluminum
 

I'm not questioning you guys knowledge but just curious as to how media blasting compromises the strength of the wheel? Reason I ask is cause there's no heat involved during this process.

Well with a whole lot of work I got three wheels completely polished out. I think my description may have been a little extreme. In the picture below the wheel was sanded with 400 grit wet paper.
Attachment 450020
With soda blasting it was completely smooth already.

In order for me to get the surface completely smooth i had to use the 80 grit. Here's the finished product.
Attachment 450021

Re: Ways to remove heavy pitting from aluminum
 

Well, to be honest, it has everything to do with the microscopic construction of the aluminum. As it is impacted, it deforms its structural make-up, weakening it at an almost chemical level. Its really not something you will be able to see easily.

Re: Ways to remove heavy pitting from aluminum
 

Gotcha. This is something I've never heard of. I don't think these were damaged on that level though.

Re: Ways to remove heavy pitting from aluminum
 

wow..those pits are rough..they used pea-gravel media? lol
makes my fingers hurt just looking, I feel u man.
One more left, huh? Maybe something mechanical..there's all sorts of buffing heads for most tools...we had some of those eraser-looking ones at a machine shop that are cylindrical and work in tight spaces..some u have to use sticks of rouge. <- (little Francais for u)

Re: Ways to remove heavy pitting from aluminum
 

Bud, sometimes there's no way that you would know it just by looking at the wheels. Its only once the wheel cracks/breaks that you'd be able to see the weakened structure.

Re: Ways to remove heavy pitting from aluminum
 

Well believe it or not they're all done. Took about 8 hours per wheel and they are far from perfect. Toyomatt being as though these are forged how much damage do you really think occured judging from the pic?
Attachment 449990

Re: Ways to remove heavy pitting from aluminum
 

Bud... I have no idea how much damage was done. That's the nature of it being "microscopic" damage. If you want my honest opinion, I wouldn't use them for more than a fancy coffee table at this point.

Re: Ways to remove heavy pitting from aluminum
 

Forged wheels have a certain molecular structure where the molecules are in-line (parallel) with the general shape of the wheel. The blasting upsets this structure at the boundary of the material (the outside where the media hit it), so this is a great place for cracks to form. Guess what else you get with aluminum? A much more brittle material than steel, so these tiny cracks are very capable of travelling all the way through the wheel's spoke....which you don't want :P

You can kinda get the idea from these pics:

http://www.scotforge.com/images/photos/graingrowth3.gif

https://www.amgaustralia.com/admin/O...%20process.gif

http://web.tradekorea.com/upload_fil...52660_sub1.jpg

Re: Ways to remove heavy pitting from aluminum
 

Maybe it's not all bad...since you're polishing afterwards

http://www.peachparts.com/shopforum/...oy-rims-2.html

Re: Ways to remove heavy pitting from aluminum
 

The problem with your method regards the removal of material.

You're simply stripping away too much of the wheel! Media blasting hurts enough, but to continue sanding each wheel for up to 8 hours seems a little extreme. I've painted almost a dozen sets of my own wheels. They take very little preparation!

My colleague seems to think your wheels may still be usable, though they should definitely stay OFF the track. Just like someone else said though, it's impossible for us to really tell ... Only the wheel knows now! ;)

Re: Ways to remove heavy pitting from aluminum
 

You have to remember I was polishing each wheel by hand. I started with the 80 to remove the pitting which didn't take very much effort at all. Then I went to 150, 220, 400, 600, 800, 1000, 1500, then finally 2000 grit wet paper. After that I hit it with some Meguiar's ultimate compound to remove any leftover fine scratches. After that I used some busch metal shine. The technique in which I was using is what took so long. That was eight hours from start to finish with breaks.

I consulted with a local wheel company and he assured me the pitting wasn't bad enough to cause anything but cosmetic damage which I've repaired.

They're fine to me but I guess your right "only the wheel knows" lol.

Re: Ways to remove heavy pitting from aluminum
 

This statement as a generalization is wrong. Soda, glass, walnut, plastic beads, etc... are a completely acceptable media to strip an aluminum wheel. Honestly, a low grit AO would work as well as long as it's just enough to rough up the substrate so that powder coating has something to bite on.

If you just want to remove a previous coating though (in order to paint or polish the wheel), unless it's 5 layers deep of paint/powder or worse...chrome/dipped finish, just have it chemically stripped. It's cheaper and easier.


Steve

Re: Ways to remove heavy pitting from aluminum
 

Forced media blasting doesn't differ in the method of alteration it does to the material it is being used on. Yes, softer medias will not penetrate the metal as deeply, but there is still penetration and alteration of the metal's construction regardless of how soft or fine the material being used is. It may not be visible to the naked eye, but there are definitely alterations being made.

Re: Ways to remove heavy pitting from aluminum
 

Well, I guess that's important for space travel, but it can't be any more aggressive than acid rain, daily use, etc...


Steve

Re: Ways to remove heavy pitting from aluminum
 

I will whole-heartedly admit that I got a good laugh at your first remark. :)

As for the damage incurred by media blasting, you can assume what you like. I'm one for being more than overcautious when my life is on the line. ;)

Re: Ways to remove heavy pitting from aluminum
 

I'm glad, because it was definitely meant as such. :)

I used to powder coat back in the day and I can tell you that I would have long discussions with peers regarding the correct way to process all kinds of various materials (including being VERY careful media blasting magnesium wheels since a spark from the blast surface COULD ignite the dust in the air).

I understand and appreciate your caution, but IMO, it would only matter when you really need to min/max values for a specific purpose like endurance racing or abusive environments. Otherwise it's not like not taking a road that big trucks travel down a lot. The chance for debris and road damage is higher, but the likely hood that you'll be part of something like that is slim.

Again, just my opinion. :)


Steve

Re: Ways to remove heavy pitting from aluminum
 

Since I use my wheels both on-road and on the track, I just like the peace of mind that comes from chemically stripping a wheel (as opposed to media blasting). With anything though, there are tons of variables that one can not plan for (no matter how cautious they are).