After addressing some rust issues under the lip of the front hood, bottom of rear tailgate and the rear part of both rear wheel wells, I was actually impressed at how well these area resisted corrosion in the rust belt despite lack of regular treatment. If they had been addressed proactively by the previous owner with a few squirts of oil spray in the right holes and a treatment of grease on the wheel lips on a yearly basis, I think about 80% or more of the corrosion could have been avoided. DIY cost would have been about US$5-10 per year. That said, there was apparently a paint or prep issue at the factory and what appears to be an overlapping seam design issue on the wheel wells that would trap water and expanding ice which certainly did not help. I used POR-15 and paint along with 3M spot putty on exterior surfaces where appropriate. The inside of the wheel wells along the outer lips received a heavy coat of lithium grease. The repairs should look good for a few years or at least or until the vehicle has little or no residual value.