If stainless steel is rusting in your pocket, any sort of artificially emulated 'patina' isn't likely to change that anyway; it'll probably make it worse. Stainless already 'patinates' (oxidizes) in it's own way, forming a thin & clear (i.e., unseen) layer of chromium oxide on the surface; it'll always do that, no matter what the finish on the blade is. In fact, the reaction of the chromium to oxygen is faster (essentially instantaneous), and it'll likely inhibit or prevent the reaction of iron to oxygen (which is what makes the dark oxide 'patina' in plain carbon steel). The chromium oxide layer formed is probably the best rust protection the steel will ever have, and if that's still not fully protecting it from rust, an artificially created acid etch (which isn't patina or oxide at all) isn't going to do any better.
Oiling the blade would likely make 99% of the difference in adding some additional protection. Polishing the blade will also make a difference, as a finer finish is less likely to trap & hold the stuff that contributes to rusting; moisture beads up and has a tougher time clinging to a highly-polished surface. Acid etching will do just the opposite; it'll create deeper pits in the steel, which darkens it, and which will be MORE likely to hold moisture, dirt, salt and all the other stuff that makes rust more likely to occur. The best example of that is the rust often seen on bead-blasted stainless blades, which do look darker, but create a rough-finished haven to trap & hold all that rust-making stuff.
Patina works to inhibit rust a little bit on non-stainless steel, only because non-stainless steel has literally nothing else working to protect it, like the chromium (at/above ~12%) does for stainless steel.
David
