Busy day today

This one says the product of rusting is ferric hydroxide, not just ferric oxide, so it uses the hydrogen in the water. They didn't say things like that to junior high students when I was one. Or maybe they didn't say it to anyone then?

Another page I looked at also called water a catalyst.

The big problem with cars rusting is that oxidation is accelerated with salt. Most important thing is to wash it off.

It has been years but I saw the processes used to rust proof car bodies. They might use one side galvanized steel as two side is tough to weld. I recall noting that Renault would take the welded body and galvanize it.

After the body is welded and cleaned it is dipped in a phosphatizing coating. Then an Electro-coat paint operation (ELPO), this stage essentially helps in depositing a primary anti-corrosive coating of paint. Then car is painted with color coat and clear coat.

In the early days of this process some manufacturers were getting bubbles under fenders not getting coating and fender would rust out from the top. At a Chrysler plant I saw them remedying this by spraying under the fenders.

If these coating are abraded or scratched off steel can rust.

Not sure they do as much with the undercarriage but there are coatings that can be applied. Superficial rust is not a big problem but in bad regions where roads are salted the whole frame can rust. That is why washing the car is important.

Some of the equippment DOES rust - the equipment where salt gets trapped AND the equipment gets into "fresh" air - or into sections of the minethat are "briney"