Hmm, I wonder how long it would take. I know that the Delorian's outer shell is made with stainless steel and I've heard that will never rust, or not for a very long time. I know that they recommend putting an anti-sieze compund on the threads to prevent galling. I found a website that has all stainless steel kits for different vehicles, mostly older and antique, but they must have individual hard to find bolts. (
http://www.totallystainless.com/). On thier site they claim (Stainless is a series of alloy steels which contain at least 12% chromium. Such steels will not rust when exposed to weather. ). I'm sure after years and years and in very salty environments it may rust, but like you said, probably not for a very long time. I wonder if they would outlast the car?