Steel patina?

[rookie4real]

I know that some high carbon steels, such as A-2, with exposure to elements will develop a patina on their surface.
As I understand this layer of light surface oxidation actually protects the steel from futher corrosion, simmilar to characteristics of Titanium/Aluminum.
Can somebody confirm that and may be provide some link(s) to a study/experiments supporting this?
Anyways, my main question is: Can M-2 steel have patina or it goes straight to a red rust, just like D-2?

 

[J.Mattson]

I’ve gotten spots of patina on some of my d2 blades

 

[Joshua J.]

Here's my Benchmade 140HS (M-2) that I stripped the coating off of.

The first thing I did was soak it in vinegar for half an hour after removing the coating. I just keep it dry and oil it every once in a while. It hasn't rusted yet, though it is a fair bit darker now than it was a few years ago.
On the other hand the 710HS that I stripped the coating off of but did not give a patina, sat in a zip-lock bag for a few months and got some light surface rust (rubbed off nicely with a scotch brite pad).
I'm pretty sure the patina does indeed protect from rust. If you want to take it a step further get some gun bluing stuff. I hear it works even better.

I also put a patina on my BM211 (Bare D-2). Never seen rust on it either.

 

[rookie4real]

I’ve gotten spots of patina on some of my d2 blades

From what I read, I thought they don't. I guess , I was wrong.

 

[rookie4real]

Here's my Benchmade 140HS (M-2) that I stripped the coating off of.

The first thing I did was soak it in vinegar for half an hour after removing the coating. I just keep it dry and oil it every once in a while. It hasn't rusted yet, though it is a fair bit darker now than it was a few years ago.
On the other hand the 710HS that I stripped the coating off of but did not give a patina, sat in a zip-lock bag for a few months and got some light surface rust (rubbed off nicely with a scotch brite pad).
I'm pretty sure the patina does indeed protect from rust. If you want to take it a step further get some gun bluing stuff. I hear it works even better.

I also put a patina on my BM211 (Bare D-2). Never seen rust on it either.

That's one of the most beaten up/used knives I have seen up to date. Great pictures by the way. I will that bluing stuff a try. Thanks.

 

[Joshua J.]

That's one of the most beaten up/used knives I have seen up to date. Great pictures by the way. I will that bluing stuff a try. Thanks.

I guess it's worth mentioning that gun bluing actually turns steel a dark shade of blue.
Keep that in mind before applying it to any high end knives you don't necessarily want in that color.

 

[PrimitiveMan]

I use cold blue on my Case CV blades. They turn out great looking and it lasts until they gain a natural patina.