They can be caused by anything from running into a curb or driving over debris on the road. But as long as your alloy rim damage is mil you can usually repair it yourself. Spend time cleaning your tires before you fix the damage so that any repairs you make are as permanent. Though out of wheels can be repainted with pure silver, test the spraypaint out on a small portion of your wheel to see if it matches.
If not, gradually add some black paint and re-test until you get a match. Learn how to repair your rim and remove curb rash and scratches with this simple, step by step video.

Scraping your rim against the curb is no fun, and the damage can cost a lot to fix until now. When you leave the scratch unattended for an extended perio corrosion will take place, and this will speed up the build-up of rust, therefore, compromising the quality of the entire rim. This wheel repair works on your aluminum alloy and steel rims no matter how deep the scratch or how bad the curb rash.
Repair scratches in alloy wheels by cleaning the surface, applying filler and sanding until smooth.

