Yes - something acidic to pickle the surface, and clean any loose hydrated iron oxides (Fe2O3·nH2O) i.e. "flakey rusts" away, to first get a blotch-free surface. Now the game is to lay on some high adhesion rust Fe2O3 and convert it to another kind of "rust", Fe3O4 , called magnetite.
Without adding in any other elements, just boiling in water, or promoting a high adhesion corrosion with a powerful oxidizer like peroxide, makes, a (thin) coating of magnetite, and it can end up gun-metal blue-black colour. It blocks the direct exposure of iron to wet air. In doing this, you have to follow through until you have the coating. Any iron that has seen any acidic cleaning will turn orange before your eyes in seconds. This also happens if you have been steam-cleaning. Leave the stuff under the liquid, or get the process to continue until the surface is protected. The recipes vary, but this intermediate stage always leaves the iron/steel vulnerable.
Without going into the generally complicated chemistry of iron oxides and hydroxides (the flakey stuff), or the zillions of recipes for adding in other solutions or heat processes to get a special color, in general these coatings are stable, but not really permanent. If you seal it with a penetrating oil, you have a very durable blue-black surface. This is not to be confused with "rust converter" products that use phosphoric acid to pickle off the rust, and then cover in some of their own oxide (ferric phosphate). It's also blue-black.
We recognize a mad mixture of all these oxides, including magnetite as mill scale. A fresh mill scale is hard, and protective, and if sealed, can be attractive, but if left to itself, it will rust through and fall off. The stuff is quite useful, until you want to weld on it or machine it.