Most if not all the rust inhibiting products on the market contain a zinc phosphate additive. This is the same additive that some of the paint products mentioned in the earlier posts. As for the Golden Gate Bridge, there are a few reasons. It would be costly, a controlled enviroment is preferred for the proper application of this type of product and containment during application of phosphoric acid on such a large scale could be hazardous as well as a liability. General Motors and any other auto makers would have no reason to make an automobile last forever. Therefore it would be not cost effective to treat the sheet metal for lifetime corrosion protection.
