Sure it isn't just salts built up? Aluminum and magnesium will oxidize/corrode to a whitish color, powdery, but steel turns reddish even before it flakes away. Try scrubbing it down really good first with a really powerful cleaner (Maybe full strength orange oil cleaner, simple green? guys- what would cut the salts well? My forte' is mostly household messes... (; maybe even baking soda?)
If it is indeed oxidized, then yes, it will eventually corrode (note that 'rust' is the common term, but only refers to the color of corroding metal. Most people I know call it 'corrosion'.)
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here'sa good article on how this occurs.http://www.tc-11.com/Fundamentals_of_Corrosion.htm another good article oncorrosion (note that the lower half seems to be an ad for a corrosioncontrol product, not necessarily automotive use.)Might be a good idea to have the car treated with a 'rust proof'undercoating by a reputable company, making sure that it is warranted andthat they clean the oxidation off prior to spraying everything. Could becostly if they have to clean everything first though. Never lived in a snowyclimate to know how much that stuff sets you back. ;) There's probably a lot of products out there to clean the metal of oxidation, and all claiming to be better than the next with price tags to match the claims. I know the Navy just sands off the oxidation/corrosion and paints over it, and it seems to work fine for their multimillion dollar fighter jets and ships. (If it is extensive enough, they have compounds to patch it with.) So try sandpaper first, WD-40 around the bolts to get them off and protect them once they're clean (and if they break, drill em out and replace them, and deal with it. Small cost to protect the metal around them.) Then if you're still worried, apply a barrier film of some sort. Shoot it all with black paint if you fancy.