There a significant differences between big rigs and pickup trucks and cars in terms of the number of hours on the road each year exposed to all sorts of things, not to mention the types of coatings on the aluminum. Many big rigs have polished or brushed aluminum parts such as fuel tanks and steps that rely on the naturally occurring aluminum oxide layer that forms to protect the base metal. Most passenger vehicles using aluminum body panels will have coatings on them to prevent or at least reduce corrosion. Some of those coatings are proprietary, and no doubt some use a combination of anodizing, etching primers and paint.I recently read that the liquid de icer used in some states is causing issues with aluminum corroding. Normally aluminum builds a oxide that protects itself but the chemicals in the new de icers cut through that and attack the base metal. Seeing damage on big rigs that are using aluminum in those states at this point.
Aluminum wheels have been used on cars and truck for decades, but they typically have a clear coat or paint to protect the substrate from corrosion.