[HoosierDaddy]

What I have seen on my Newells is called filliform corrosion. Typically caused by something like a stone chip breaking the paint surface then moisture becomes trapped below the surrounding paint. The corrosion is a white powdery substance. There are two spots on my 1993. I scraped the paint totally off of the surface and it hasn't spread. It is generally not considered a structural issue. There are solutions for this condition. I would talk to a body shop that is certified to repair Ford aluminum truck bodies. Galvanic corrosion results from two dissimilar metal being in contact with each other. The addition of any moisture will aid the corrosion. I believe Newell uses some kind of an adhesive barrier between the metals in the areas where aluminum and steel are joined.