Rusting is a common form of corrosion, which occurs when metal atoms react with their environment. Salt water does not make a metal rust, but it accelerates the rusting process because electrons move more easily in salt water than they do in pure water.

Does salt increase rusting?

If we recall, rusting occurs due to a chemical process known as oxidation where metal atoms tend to lose electrons and form ions. So, when we add salt or salt solution (containing ions) it will accelerate the rusting process by allowing electrons to move freely or easily flow from iron to oxygen.

Does dry salt cause rust?

Salt alone doesn't create rust; it also requires moisture. Think of all the rusty cars in beach towns. Moisture, mixed with salty air from the ocean, is a perfect recipe for rust. Salt brine mixed with humidity can create the same effect.