Is M4 the most rust-prone steel?

Cassull

Cassull

Joined
Mar 31, 2012
Messages
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I own my fair share of carbon steels, but it seems to me M4 is BY FAR the most rusty steel I own. I bought a Demko AD20S in M4 and I keep it well maintained. But if so much as a drop of moisture finds its way on it, it'll have a permanent rust spot in the blade for the rest of its life. All my Winklers that I keep much less maintained in 80CRV2 are all rust-free same goes with my 1095 camp blades.

I just checked my M4 blade last night after having it stored in a dry place for a week and the spine had a bunch of rust spots starting to form. I rubbed it through my strop and it got rid of it all, but still, amazing how easily it rusts.
 
Interesting, that site has 1095 as being the worst. Maybe it's just the finish on the blade on my Demko that makes it more vulnerable to rust? I didn't think it would since it's just a basic satin finish.
 
Cassull said:
Maybe it's just the finish on the blade on my Demko that makes it more vulnerable to rust?
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I also wonder about whether that could have a meaningful effect on rust resistance. Is a smoother more polished finish less prone to rust than a coarser finish? Is there any testing to support or refute such a hypothesis?

edit: ah, from the previously linked page: "a rough finish leads to faster corrosion, in general the finer the finish the better the resistance to corrosion."
 
Steels that rust do so differently as well. 52100 rusts with deep pitting, while V4e I've used developes bright orange rust on the surface without any pitting whatesoever.
 
Guy McVer said:
edit: ah, from the previously linked page: "a rough finish leads to faster corrosion, in general the finer the finish the better the resistance to corrosion."
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Makes sense, a rough finish leaves much more (micro) surface area on the knife which leaves more area exposed to oxidization.
 
I have a pretty good supply of M4 thanks to Blade HQ and Spyderco. None of it is coated and none is rusty. I do force a patina on any new one I get.

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Cassull said:
I just checked my M4 blade last night after having it stored in a dry place for a week and the spine had a bunch of rust spots starting to form. I rubbed it through my strop and it got rid of it all, but still, amazing how easily it rusts.
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Do you live in an area that is prone to high humidity levels? Perhaps near saltwater? Do you have a hygrometer?

Danke42 said:
force a patina
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This is not an uncommon practice and maybe worth trying. A lot of people use yellow mustard. Straight vinegar will probably work better but it may look ugly. I've seen some really cool looking effects that people have achieved with mustard but it might be less effective or take longer depending on the steel. I don't really know a whole lot about it though because I've never actually done it myself.

 
My GB2 shows only a few minor spots after a couple of years. I rinse and dry it after cutting food but don't bother with any rust protectant.
 
Guy McVer said:
Do you live in an area that is prone to high humidity levels? Perhaps near saltwater? Do you have a hygrometer?
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No, I'm in New England miles away from the sea. It's starting to cool now so the moisture is very low.
 
I would still get a hygrometer and keep it with your knives just to be sure. There are multiple reasons why it's good to know what the humidity levels are in your home. I have 3 hygrometers in different places. The humidity level can vary from room to room and sometimes it varies from one side of the room to the other. I'm thinking of getting another hygrometer for the outside just to see the difference between the indoor and outdoor levels.
 
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