CPM-440V and Rust Resistance

J

James Y

Joined
Feb 18, 1999
Messages
6,496
In the new issue of Tactical Knives, in Jeff Randall's review of the Military, he states that unlike most stainless steels, it did not rust in the jungle environment. This really caught my attention because, although I don't currently own a knife of 440-V, I had the impression it had less or similar rust resistance to ATS-34. He also lists the Military at 55-56 Rc. Might that have something to do with it's superior resistance?

Strangely enough, in the same issue, Chuck Karwan reviews the CS Scimitar, which uses AUS-8A, supposedly more corrosion resistant than most high-carbon stainless. He states his picked up some minor pitting from some blood and barbecue sauce.

I'm certain the Military was put through far more extreme use and conditions than the Scimitar in the same issue. Is CPM-440-V capable of resisting rust with only minimal field care?
Jim
 
I've read one or two other threads which have referred to 440V or 420V as lesser-resistant steels among the "stainless" varieties. However, my understanding is rather the opposite: that both (and 440V specifically) really push the envelope on corrosion resistance in steel. (440V and 420V have about 17% and 13% chromium, respectively.) That is why Tom Mayo in Hawai'i, who is keenly concerned about corrosion, enjoys working with these two CPM steels.

On a related point, however, Tom Mayo has also noted twice (that I'm aware of) that, below 56 RC I believe, 440V loses much of its corrosion resistance. Anyone know why?

Glen
 
One of the reasons I bought the Native was to use it around water while fishing. As stated, it has a ton of Chromium which also adds to the hardness.

Perhaps when Sal returns from Oregon he can comment on why heat treating below 56RC would lead to corrosion. Perhaps it has something to do with the size of the granules.
 
The process that keeps 440 series steels from rusting is a surface coating that is created instantly by the chrome in the surface of the steel. Even when washed off, as soon s the surface of the steel again is touched by air, it again recoates the surface the steel. It is a type of oxidation process.

This process does not seem to work when any of the 440 series steels are not hardened. I know this is true in the lower rockwells (40's). Have not heard this of 440V below 56.

Hope this helps.

sal
 
Thanks for all the replies, everyone!
I love learning about all these different aspects of knives.
Jim
 
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