How much does a patina actually protect against "bad" rust?

[SubSpace]

Just a sciency type question. I've seen some heavily patinad knives with red rust spots on them. Does forcing a patina really do all that much towards protecting a blade from the red stuff?

 

[WSB master]

Yes it does help prevent rust. But it does not make it 100% percent safe against rust. It just makes it basicly more resistant to it making carbon steel care easier and less of a hassle.
I noticed if you patina a blade and keep the blade well oiled (I use baby oil) your knife is almost invincible to rust.
I patina can also look really cool i reccomend you go on youtube and check out gavkoo's videos on patinas there is one with him doing one on a bk7 and another on a bk11 and they both come out tight!
He also shows you how to do it step by step!
So basicly in conclusion i think patinas are a good thing and you should do it to your knife, especially if you use it outside a lot.
Have a nice day let me know if this helps!

 

[KennyB]

In my experience a patina does two things:

1. Makes it a little less likely to form ( but if it gets too wet, all deals are off)
2. Makes taking rust off a lot easier.

On a blade with a patina, some red/brown rust will form in conditions it normally would, but whatever the science is, it almost rubs off with your fingers if there is a patina underneath.

Otherwise, a patina mostly seems to fend off rust in humid environments. If you put a wet knife away in a sheath it will still rust, but it does help against normal atmospheric moisture.

 

[db]

Don't know the science behind it, and some will say rust doesn't stop rust. However, I put a patina, black rust on my Opinel and the red rust problem I was having stopped.

 

[Magnaminous_G]

It depends on the patina. If it's a very light forced patina, fingerprints will rust right through it. The most protective patina is a natural patina formed over time from regular use. The following is a pic from BF member bearthedog. Look at the Nessmuk in the bottom. That is not/not heat treat scaling. That is a natural patina formed over time with regular use, and if you check out his travel threads (where he takes his knives all over the world into the dessert, jungle, mountains, etc.), you will see how much he uses his knives. But basically, this kind of patina is very protective. I'd say all he probably has to do is wipe the blade down after use and it probably is pretty corrosion resistant, despite being made of O1 (I think).

Pic by bearthedog

EDIT: Here's the original knife! Pic by bearthedog

 

[t1mpani]

Those who would say that it does nothing at all are apparently under the impression that gun makers all over the world, independent of each other, came up with browning/bluing hundreds of years ago for no reason other than they were bored, and those who bought their wears payed for this added process/expense because they were just anxious to give away what little money they had. The people who believe this happen to not be very bright.

Modern coatings and stainless steel are, of course, superior in resisting rust to a blued carbon, but a patina does indeed help. The much rougher surface of oxide also helps a blade hold onto oil or wax much more easily than it will when brightly polished.