… bridge, or a large container ship.
Well, sort of. If your van has any amount of rust that needs to be treated there is an excellent marine product called ‘Aquasteel’ that converts rust (Ferrous oxide) into an inert organic ferrous compound that is claimed to be environmentally safe.
It’s very reasonably priced at around £18/L direct from the company of the same name. It is water soluble, is clean and easy to apply, is water-based and goes a long way (12m^2/L). It also does an excellent job, although that’s not to say that there aren’t other. equally good, products on the market.