I put some iron nails in water, and obviously, those started oxidizing, making those hydrogen bubbles. Some days after, the water was orange, indicated that the FeO has just dissolved in it. I found some days after that the solution was oversaturated, and the insoluble FeO was at the bottom of the container. I need all the FeO, even the one solved. If I heat and evaporate the water, will I lose the FeO? Or will the water leave it alone to use? I think I would get steel 0.2, but I am not sure.
It is not FeO ( ferrous +2 iron), ferrous is unstable in the presence of air. And FeO is black as high temperature mill scale. You have a ferric ( +3) compound , likely some kind of hydroxide. The lab I worked in analyzed ( XRD) at least one "rust" sample a day for corrosion evaluation. The iron compounds were generally not easy to pin down to a specific compound using the Fink XRD Index.