Aluminum is one of the most versatile metals out there: you can find it in everything from cookware to appliances, car wheels and trim, and more. The down side, however, is that it tends to become discolored and dull over time. Aluminum is also prone to corrosion, which also dulls the finish.
The best way to prevent aluminum from dulling is through regular maintenance and cleaning, but if you haven't been able to give your aluminum components attention until now, it's not too late. In this article, the abrasive technicians at Red Label Abrasives have compiled this full guide on how to polish aluminum and keep its finish in prime condition.
You will need the following items for most aluminum polishing jobs. This list will vary based on the size of the job, the type of preparation required, and your preference in cleaning and polishing aluminum products.
Prior to polishing an item, you should clean it to get rid of dirt and grime. If the buildup is minor, you can usually do the job using mild detergent: simply remove all debris by washing the surface, rinsing it, and wiping it dry with a paper towel or clean, soft cloth. If it looks good after this simple step, you can go straight to polishing it. If not, proceed to step #2.
Pro Tip:Some objects, like cookware, can acquire a coating of grease that thickens over time and can be difficult to clean off. In this case, use a detergent with a degreasing agent, such as Dawn liquid dish soap, or a commercial degreasing agent.
If corrosion or other buildup remains after a simple cleaning, you will need a different product to remove them. There are several kinds of commercial aluminum pre-cleaning products available to remove corrosion in particular.
Once the treatment has been applied, allow it to sit on the metal for a couple of minutes to loosen the buildup. Then rinse it off. Repeat the process if there is still buildup, using ultra-fine steel wool or a stiff brush to loosen the debris. Repeat as necessary, then rinse the object with warm water and dry it.
In some cases, additional prep work may be required beyond degreasing and cleaning. Surface flaws resulting from severe discolorations, scratches, or pits cannot be corrected with polish. For smooth surfaces, sanding may not be necessary, but for rough or uneven surfaces or those with scratches, sanding may provide the desired result.
After applying masking tape to areas that you don’t want to sand and putting on protective gloves and goggles, start with a lower grit sandpaper, especially if the aluminum surface has deep scratches or stains, and work your way gradually to a finer grit.
In most cases, a 320-grit abrasive will do the trick, but if you’re dealing with deep pits or gouges, you may need to go with a lower grit in the 180 to 250 range. Use progressively finer sandpaper as imperfections are cleared away and the aluminum surface prepared for polishing. In most cases, you can start with a 320, go to 400, and finish with 600, although you can go as high as 1500 grit for maximum polishing prep.
Sanding can be done by hand, with an orbital sander, or a combination of the two. The smaller aluminum pieces can be sanded by hand with sandpaper, but for bigger projects, you'll need a power tool. An angle grinder with an aluminum grinding flap disc or orbital sander with pressure-sensitive adhesive sanding discs are recommended for best results.
You can either purchase commercial polishing products or make your own with ingredients that are readily available. (Note: Anything you might use to prepare food shouldn't be polished with commercial aluminum polish, which contains toxic chemicals.)
If you prefer, you can make an aluminum polish for cookware using vinegar and water. Simply combine equal parts water and white vinegar in a spray bottle and apply the mixture to the aluminum surface. Then use a soft cloth to wipe the surface clean. To increase the shine, you can also use a fine grain steel wool buffing pad to smooth the surface even further.
You can also make homemade aluminum polish by combining equal parts cream of tartar and water. Apply the mixture to the aluminum surface using a clean cloth and making circular motions. Before the polish has a chance to dry, remove it using a clean cloth to create a brilliant shine.
You can polish your aluminum by hand or using a machine; the recommended approach will depend on the size and condition of the workpiece.
Typically, when smaller aluminum surfaces are dull but do not show significant oxidation, rust, pitting or burns, you can use a good hand polish with a microfiber applicator to give them a quick shine. If you're tackling a large object and using a commercial polish, it’s faster to use an angle grinder with buffing wheels.
Add a bit of coarse abrasive compound to your stiffest buffing wheel. Buff the entire surface in sections, adding more polishing compound as needed. When you've finished this step, wipe the residue completely off and change your buffing wheel, as you don’t want to mix abrasives.
As with sanding, start with the coarsest abrasive and work your way down. You can start with a gray metal buffing compound bar, which is formulated for cutting non ferrous metals and reducing imperfections, and follow with a brown tripoli, which does an excellent honing job on aluminum. For a mirror shine, finish up with a white rouge buffing compound and give the workpiece a final wipe with a clean cloth.
Most aluminum alloys are soft, so you’ll need to use abrasives that are appropriate for sanding aluminum. They include:
Pro Tip:To keep your abrasive products in the best possible condition, apply a grease stick to the surface of the moving abrasive disc or sanding belt. The grease acts as a lubricant and prevents aluminum debris from sticking to the abrasive grains. It is also recommended that you use an abrasive cleaner, which is a rubbery stick that removes loading from the abrasive surface.