I recall friends' in Snow Belt states needing to undercoat their cars every year with a tar-like substance to protect from road salt corrosion -- would this method help slow down or even prevent the problem? ...or would it transfer the corrosion to another dissimilar metal spot?
Just a thought game, also, what is the possibility in creating a sacrificial anode/cathode part in a mounting point to an engine or chassis ground? Are there examples of this in other machines/industry from where it can be adapted?
The problem boils down to a poor choice of materials.With 20/20 hindsight, choosing foam pads that hold moisture against the steel gas tank was not a good idea for the long term. One could make the argument that C/C was not worried about how long his cars would last as long as you could win now. I don't know what Mclaren's excuse is. They should have known better. On the plus side it took a LOT longer for it to be an issue with Lotus.
There are multiple types of corrosion, some aluminum alloys are highly corrosion resistant, others not so much. Coatings are only as good as the life or integrity of the coating. Cathodic protection can help but only under certain conditions. Unfortunately the tank surface, the wet insulation, and the chassis can behave like a battery.
When I said "poor choice of materials" I was referring to the choice of foam for the pads. They could have used some closed cell type that wouldn't hold water. As for plastic tanks, Lotus was familiar with the technology, when they designed the Delorean they used a (wait for it!) PLASTIC tank! That was back in 1979 and way before anyone was thinking about Ethanol. Turns out to have been the exact right choice. FYI, they used foam pads but they are closed cell and don't hold water (doesn't matter against the plastic tank). Sometimes you don't learn from history or maybe they just took a short-cut. Bean counters (aka accountants) have been known to do that kind of thing. Besides, no one was designing the car to last this long. If they did no one could afford to buy one! It is called an "engineering compromise" when you build to a certain price point.