I know I'm responding quite a bit after the discussion has more or less ended.......but has anyone thought to try using Sanchez no-oxygen product.
It evidently works by not allowing oxcedisation to occur. People swear by the product to stop oxcedisation of track thereby improving electrical contact. So just maybe it might protect couples from "rust" build up in lightly used couplers.
Then again it "may" cause couplers to not work at all.
I figure it has got to be worth a try. Given that we can't get rust oleum in the right colour here in OZ I think we have to find a solution for this problem.