How To Polish Aluminum Wheels
This article will help you to get the best results out of cleaning and polishing your aluminum wheels.
But first, if they are magnesium alloy
(mag alloy) you can forget the polishing bit unless they contain less than 20% magnesium. I don't care what any other polish manufacturer tells you. Magnesium is white and will not polish. If anyone tells you they have a mag alloy polish, it's an aluminum polish. Your mag wheels will come clean with a wash, and if you have used an acid or they are oxidizing you can clean them and remove the oxides with polishes, but magnesium doesn't shine.
If you are using liquid polishes or pastes, be sure that they do not contain ammonia, anhydrous chemicals or acids. They are detrimental to your workpiece.
Ammonia and anhydrous chemicals prematurely age metals, cause tarnishing and rampant re-oxidization. They are used by many manufacturers to attack oxidization and generate follow up sales, as they look great for a week or two, then the ammoniates or anhydrous goes to work and does a wonderful job of fading quite evenly. The trouble is these chemicals continue the oxidization process too, and often etch into the metals - which is even worse.
English Custom Polishing does not use ammoniates or anhydrous products but knows of many manufacturers that do. Infact probably 90 percent of the polishes on the market contain ammonia, anhydrous solvents or acids. Read the labels and avoid the products that do.
Basically the problem is Zinc which is often present in aluminum in large quantities and is dissolved very easily by ammonia, the related anhydrous chemicals and acids.
Now let's get on with the process.
First move is to take the wheels off. Then you can get to everything. This will allow you to ensure that you can see and reach every part of the wheel.
The next move is to remove all road grime and dirt. Greasy Joe oil, grease and crud remover will do that and it will prepare your wheels for polishing. Make sure every part is clean and dry. You need to clean between every stage, so an abundant supply of clean terrycloth is necessary. If the surface of the wheel is pitted the pits can be removed with a foam painter's abrasive pad. Using the finest grade you can buy or about a 400 grit wet and dry paper. Never sand aluminum with anything coarser than 180 grit. The scratches are too deep.
Test your surface first. Go to one of the worst areas and try out a 600 grit, then a 400, and so on, to ensure that you only use an abrasive as coarse as is necessary. Don't go crazy, you don't want to ruin the face or the unbalance the wheel. Be careful not to rock or put gouges into the surface. A belt grinder will also do a good job on the faces. Keep all of your strokes going in even lines around the rim and straight lines on the faces.
After a 400 grit (if that is the stage you choose to begin with) you need to go to a 600, Make sure that you remove all signs of the previous cut each time. Where possible this is best achieved by going at 90° to the previous cut. If you can see scratches now you will definitely see them when you are finished.
If you are using rotary tools you can start using something like the Beartex Avos system, or a unified wheel of medium abrasive and then go to the fine grade. The bigger the cutter the more stable it will be. We like to use 7" cutters.
After this go to the roloc type discs working from coarse to 2f fine. Again go for the biggest you can get which at the moment is about 4" diameter. Stability is the biggest problem with these types of tools and it is very easy to wrinkle or gouge the face. Be CAREFUL!
We will use any and all combinations of the above machines and techniques as and when circumstances allow or dictate. Wheels come in so many strange shapes and sizes with slots and ribs. Sometimes it's quite amazing how many variations there are of such a simple thing as a wheel.