So I've seen in many spots that "forcing" a patina onto carbon will make it more resistant to rust. Is that an old wives tale or is there any backup data?
I think it's often assumed to be more effective than it is. In other words, some seem to believe it'll prevent rust outright, lending a false sense of security as a result. So, depending on where one sets their expectations for it, there might be some of both the 'old wives tale' with unrealistic expectations, and a little bit of noticeable benefit if you look at it more rationally and with an open mind.
I see it's benefit in how it seems to
slow the beginning and progression of rust. A few years ago, I decided to try it for the first time on a Schrade 8OT stockman in 1095 steel. I had some doubts about how/if it'd help with rust, starting out. With the 3-blade stockman, I patinated only one of the three blades, leaving the other two 'as is', with the factory finish. I carried the knife every day in my pocket. Over time, I was able to notice rust spotting turning up much sooner, and seemingly suddenly, on the two unpatinated blades, as compared to the patinated blade. On the blades without patina, the spots would seem to turn up almost overnight sometimes, or even in the span of a few hours during the day. But on the blades to which I'd applied the patina, any spots which eventually turned up would do so much more slowly and gradually, over the span of days or even weeks.
I've patinated several more knives since then. And I do sometimes see new spotting on them, usually on knives that get set aside for some time and don't get used regularly. But even with those, the spots take some time to develop, as compared to other plain carbon steel blades I've left alone, and on which the spotting seems to happen suddenly and seemingly out of nowhere, from 'pristine' one day to obvious spotting on the next day.
