Have some dull lower legs that need a shine? Have your engine apart and want to polish the cases? This is a beginners guide to polishing aluminum - it is a basic introduction only. Polishing can be an artform in-itself. For a more complete guide, check out Caswell Plating's excellent manual:
Tools and Supplies
or a high speed hand buffer. Most drills will NOT be fast enough RPM to properly polish.
At least two cotton
, on stiff and one soft.
- You will need a minimum of Tripoli for initial polishing, and (Jewlers) Rouge to final shine. For quick polishing jobs of any sort, it never hurts to have a little SCR on hand (it's made for stainless, but work well on just about any metal).
Sand Paper - If you have real deep scratches or marks in the part, the more coarse of sandpaper you will need to get it out. For most polishing jobs, you will want some 600, 1000, and 2000 grit sandpaper.
Dremel tool or die grinder, if you have very deep gashs, damage, or welds. You may also want one to clean up pourous aluminum, like engine cases.
Saftey glasses and a mask - the fine grit from polishing is very dirty, and can easily get it your eyes. It's no fun to breathe it, either.
How It's Done
The theory behind polishing is rather simple - keep putting finer and finer scratches into the metal until you can no longer see the scratches, and it begins to shine.
Start work on the peice of metal by removing any paint, anodizing, or powder coating. Anodizing can be removed with heavy duty oven cleaner. Powder coating can be removed using this procedure.
Once the metal is clean, you may have to do heavy work with a Dremel tool or die grinder. If there are deep gashes, cuts, or welds, use abrasive bits to grind them out. For pourous metal cases or pitted aluminum, you may want to smooth it our using sanding bits.
With damage removed, you now can begin sanding. If the metal is very course or damage was repaired, begin with a heavy grit sand paper, around 400 to 600 grit. Try to sand in circles when possible, or switch directions regularly if straight sanding is your only option. Once it is smooth at this grit, then jump down to 800 or thousand grit, then again to 1000 (wet sanding), 1500 (wet sanding), or 2000 grit (wet sanding).
If the metal is already very smooth like a lower leg on front end or a kidney cover on a motor, begin sanding with 1000 or even 2000 grit, wet sanding it. Once you've wet sanded it with a very fine grit sand paper, it already should start to shine.
Now you're ready to begin polishing. Start off with a course wheel with Tripoli compound, make sure to switch directions regularly so you don't dig grains in too deaper. Use some brake cleaner or solvent to wipe off any build up of compound when done.
Next switch to the softer wheel with rouge. Apply lightly and watch the shine come out. Again, clean off. You'll want to buff by hand a little to see where you've missed. When complete, you might want to immediately wax to protect it.
That's it! Your part should have a chrome like finish. Over time and with use, the part will dull again. Simply clean off again and polish with rouge again to restore the luster.
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