Although my rims do not currently show this problem it is a classic problem with most, if not all, aluminum alloy rims. The paint or clear coat on the rim fails and ultimately the adhesion fails and so begins the process of pitting or corrosion. You can have your rims removed and refinished although it may be more cost effective to buy new ones. If it isn't too bad you can slow the process by touching up the areas with clear coat touch up.
I typically notice this problem near the wheel weights after careless tire technicians remove or add weight improperly. Age of the rim is also a big contributor. My Dodge, ahem, after 15 years has recently, within the past three years, begun to corrode where the tire bead is such that the tire needs to be inflated weekly.