Iron oxide formation and solvation

[caters]

I notice when I put my wagon out and expose it to rainwater that because it is not made of stainless steel, after a while of water exposure it rusts creating Iron oxide and Iron Hydroxide in the process.

Then after even more water exposure the rust washes off and I have steel with no rust in it.

I thought that it would just get more and more rusty until is is all iron oxide and iron hydroxide.

I also haven't noticed much expansion despite the fact that rusty steel takes up more volume than steel without rust.

Now why is this water forming rust and getting rid of rust? I didn't think transition metals like iron were soluble in water and thought that the oxygen in iron oxide would make it even less soluble in water given that O2 does not dissolve well in water even though some does.

 

[Borek]

Then after even more water exposure the rust washes off and I have steel with no rust in it.

Could be a matter of steel type. In general you are right about most kinds of steel becoming more and more rusty and the rust staying on the surface. Sure, some can drop off, but I don't remember ever seeing the rust dropping off and exposing a bare metal surface.

 

[caters]

Yeah. I thought that could only happen with a rust remover such as phosphoric acid.