I have noticed that, when exposed to water for a few days, the steel in my wagon turns into rust. After several more weeks, the rust that formed is dissolved in the water, and once I pour the water out there isn't any rust where there previously was rust.
This is unusual because iron oxides and iron hydroxides (the components of rust) don't normally dissolve in water, and so the water just keeps being reduced and the iron keeps being oxidized.
How can it apparently happen such that steel turns to rust, then back to steel with no rust, in the presence of water if rust does not normally dissolve in water?
This happens in a cycle like this:
steel + water = rust -> rust + water = steel + rusty water