A Primer on Rust
There is a nasty little secret about rust and salt. Salt doesn't really cause the corrosion, oxygen does. Salt is just there to speed the process. Rust, as any eighth-grade chemistry teacher will tell you, is a result of oxygen and iron molecules combining to cause iron oxide. Salt clings hygroscopically to steel and draws water to itself, which, in turn, causes iron ions and oxygen ions in the water to combine more efficiently and at a faster rate. That's called oxidation and it looks like rust. On raw steel, rust can actually creep up in a matter of minutes. Long term, the layer of oxidized metal holds water, which accelerates the oxidization, causing the steel to pit and eventually weaken. Leaf springs on trailers are particularly vulnerable to this corrosion. And it can happen to aluminum too, so arches, tops and the inside of many motors are also critically at risk.