polishing aluminum

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polishing aluminum

Postby bagged59 » Wed Jul 28, 2021 9:01 pm

hello, i picked up an aluminum polishing kit from harbor freight to polish my radiator fan shroud, and eventually polish the radiator. its an assortment of cotton wheels of different diameter on 1/4" shafts. i'm using it with an air angle grinder. i started with the brown compound, then the white, then the green. i got it to shine really well however there's a lot of swirls and polishing pad marks. it's hard to tell from the photo but they're there. my first guess is the polishing materials that i bought are substandard. i watched a few youtube videos but nothing solved this issue. i attached a pic of an inconspicuous spot on the shroud that i polished. can anyone offer some advice and point me in the right direction?

thanks, paul.
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Re: polishing aluminum

Postby RMAENV » Wed Jul 28, 2021 11:56 pm

Bagged59, 1st aluminum is very difficult to polish as compared to stainless. The white is usually the rouge and is the last of the compounds to use. The brown sounds like it is the cutting compound. I am thinking the green should have been used second. With either stainless or aluminum you have a cutting compound, a finer cutting compound to take out the finer scratches and the the finishing compound or rouge with is usually the white one. Never saw it in another color.

I bought Eastwood stuff and used a bench grinder. For stainless the dark grey was the cutting, the light grey was what the called stainless to take out the swirls and scratches and then the white rouge to polish. For the aluminum I believe i just used the brown from Eastwood and then the rouge. There should be videos on the Eastwood site for polishing aluminum.

Here is a whole Google page of videos... https://www.google.com/search?q=eastwoo ... nt=gws-wiz

Is this the one you bought? https://www.harborfreight.com/14-piece- ... 98707.html
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Re: polishing aluminum

Postby action » Thu Jul 29, 2021 12:45 am

Because aluminum is so soft compared to most other metal in the automotive world it is more prone to scratches and marks. This is not painted steel.
Using a machine polisher (angle grinder) can be a problem as it moves the pad so fast that it can take off material too fast leaving marks.
And the pads have to be changed or cleaned very frequently as the material picked up in (aluminum mud) the pad will then work over the aluminum. Again causing marks or swirls. The cotton pad has to be clean of any polished out aluminum otherwise you are creating more issues than you are taking out.

Owners of Air Stream trailers built around 1964 and earlier (after that they have clear coat) have the same metal arrangement. Except far more aluminum surface area. Usually they use a random orbital polisher for the polishing phase. Far less swirls because the machine is not going around in a circle. If the metal is in poor shape (oxidized) a low speed drill or your angle grinder can work to compound out the surface. Low speed and frequent pad changes are needed to take out the muck and leave clean metal. Too fast and you are taking metal and putting that into the pad and grinding metal onto good metal.

http://vintageairstream.com/polishing/

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Re: polishing aluminum

Postby bagged59 » Thu Jul 29, 2021 9:30 am

Yes that’s the polishing kit I bought. Thanks for the tips guys!

Paul
'59 Continental 2dr hardtop, burgundy, 460, AOD, 9" rear, 4-wheel Wilwood disc brakes, air ride, vintage air. purchased 7/7/06. Restoration in progress...
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