The inside lip of the wheel where the tire bead seals, is corroding. There is nothing inherently faulty with the wheels, it is the result of the snow/ice melt chemicals used on the roads in the winter reacting with the aluminum.
As CB2 suggested the only permanent fixes are wheel restoration (pricey) or removing the corrosion and sealing the bead seating area if the wheel isn't in too bad of condition.
To prevent the issue, thoroughly clean your wheels when washing your car. I have a winter time habit of running my vehicles through a car wash as often as the weather allows to remove as much of the ice melt chemicals as possible. I will, once a month go to a self service car wash and flood the under body with the hot soapy wash to remove the chemical build up a drive through wash can not reach. In the spring when the snow and ice are gone for good, I will easily spend an hour at the car wash flooding all exterior areas of the vehicle, particularly under hood, the under body, and the transitions from the metal panels to the lower cladding.
It can be a lot of work to maintain the vehicles body/wheels in an attempt to slow or stop the spread of rust and corrosion.
Is it worth it? If you keep your vehicles for a relatively short term, don't worry about it, leave it to the next owner.
