Alloy wheels look great, but are easily scuffed, spoiling their finish. If you're in this position, you could buy new alloys, but there is a very good chance you will damage them sooner or later. A much better option is to restore them, and here's how.
Remove the Tyres
It's best do all four wheels together so that they end up looking the same.
Don't be tempted to repair a rim without removing the tyre, it's more difficult and almost impossible to repair dings on the outer rim. At the very least, deflate the tyre and get the bead off the rim, then carefully mask the tyre with paper and masking tape. However, it's far better to remove the tyres completely as this makes the job much easier.
Clean the Rims
This is a critical step to ensure a successful repair.
Use a firm brush with plenty of soapy water. If brake dust is deeply ingrained, use a rubbing compound or degreaser. All traces of polish, wax, and road dirt must be removed until you reach the original paint layer.
Remove Loose Paint
If you are repairing minor damage, this step may not be necessary, but where the paint is in poor condition use a wire brush to remove all loose flakes, taking particular care in the hard to reach places.
After all the loose paint is removed, use medium wet-and-dry sandpaper (or scouring pad) to lightly sand the entire surface to provide a good key for painting.
Repair Dents and Scuff Marks
Sand the scuff marks and dents, making sure to remove all sharp edges.
Using a plastic steel epoxy putty or similar hard setting material, fill the dents and scuff marks. You will have to sand this later, so don't use too much putty but do make sure you bring the damaged areas back to the correct level. If the gouges are deep, you may need more than one coat.
When the plastic steel is dry, sand it until the surface is smooth and matches the original profile. Avoid damaging adjacent paint but make sure to smoothly blend the edges of the paint. Finish off all repaired areas with a 150-grit (or finer) wet-and-dry sandpaper.
Thoroughly clean the entire wheel again, removing any spilt epoxy and getting rid of all traces of loose paint, metal, and sanding debris. Use a solvent degreaser to remove any traces of oil, wax, polish, or brake dust.
Make sure the wheel is perfectly clean and that all scratches, defects, and blemishes have been repaired or removed.
Place the wheel on a clean, dry surface and let it dry thoroughly.
Prime the Wheel
Now prime the repaired areas. Buy the primer (and paint) from an automotive paint or accessories shop, taking time to find the right paint as you want a durable result.
You can use a spray can or spray gun. Adhere to the paint manufacturer's recommendations and spray at least two primer coats, allowing the paint to dry between each application. It's recommended that painting is done in a warm, dry place and that the wheel is slightly warmed for better paint adhesion.
Let the wheel dry in a warm, dry place, and then use very fine grit paper to remove any irregularities.
Apply the final coats, spraying two or three light coats and letting them dry between coats. Take your time and avoid streaks and runs.
Allow the paint to dry properly before replacing the tyres, giving it at least 24 hours or longer.
Enjoy the fruits of your hard work!