Come the hot and humid summer season, any of my carbon steel knives and chisels which are stored outdoors grow plenty of surface rust. I find a forced patina conveniently cleans off the rust and adds protection.
When you put a patina on a knife, you are using acid to etch the surface. Oxidized metal (rust) reacts with the acid much faster than unoxidized metal. I.e., most of the things you use to put a patina on a knife also work to remove red rust.
Due to sharpening and stropping, this patina is mostly gone by the time the hot and rainy season comes around again. So it's kind of an annual thing. When stuff starts to rust, I apply the patina.
I'm sure a thorough cleaning and application of oil and wax would be beneficial in itself. But a patina sure helps. The etched surface holds oil better than untreated metal, and that IS a good thing. A big part of the protection given by parkerizing is due to this phenomenon.
On my outdoor tools, I use actual parkerizing solution, simply because I already have some, and it is fast. In fact, I just went through this ritual the other day. A little late this year, and there was plenty of surface rust. Maybe I'll post some "after" pics.
Because they are regularly exposed to water and acids before being wiped down and returned to a climate controlled environment, my kitchen knives develop and maintain a patina on their own. But if they start to get any red rust (usually thru laziness and leaving them wet), I might eventually wipe them down and apply some vinegar... this cleans the rust off and restores the patina to those spots. Maybe you can think of this as converting bad rust into good rust.
So other than occasionally playing around with a new knife, I usually put a patina on a blade in the process of cleaning off existing rust. It would certainly help to apply it preemptively. But since the way I sharpen my knives removes a good bit of the patina, anyway, I don't often bother to do it until my hand is forced.
