M390

N

Nocturnal13

Joined
Apr 18, 2017
Messages
199
I have a Reate Mini Horizon D and I absolutely love it. It is my first M390 steel knife and I know it has good corrosion resistance although there are a few small specs of rust on the spine. I was able to scratch it off with my finger nail but it seemed very strange that M390 would do that.

I haven't really used it so it was just from touching it and not wiping the blade off. Is that possible?
 
Nocturnal13 said:
I have a Reate Mini Horizon D and I absolutely love it. It is my first M390 steel knife and I know it has good corrosion resistance although there are a few small specs of rust on the spine. I was able to scratch it off with my finger nail but it seemed very strange that M390 would do that.

I haven't really used it so it was just from touching it and not wiping the blade off. Is that possible?
Click to expand...
I don't see why it wouldn't be possible.
I work in a machine shop and there are some people that cannot touch mild steel without rusting their fingerprints onto it within hours. Perhaps you are one of those people? M390 is high in corrosion resistance, but it isn't corrosion proof.
 
Ive had rust spots on knives just from regular pocket carry and swam in the ocean with the same knife showing only similar rust spots. Go figure! I reckon it’s where a speck of something particularly corrosive, which combined with a slight amount of moisture, causes a reaction on the blade?
 
danbot said:
I don't see why it wouldn't be possible.
I work in a machine shop and there are some people that cannot touch mild steel without rusting their fingerprints onto it within hours. Perhaps you are one of those people? M390 is high in corrosion resistance, but it isn't corrosion proof.
Click to expand...
I very well might be haha. Although it hasn't happened on my satin s30v or xhp blades it might have just been one time my fingers were more sweaty. But you are right almost all steels can get rust spots.
 
archieblue said:
Ive had rust spots on knives just from regular pocket carry and swam in the ocean with the same knife showing only similar rust spots. Go figure! I reckon it’s where a speck of something particularly corrosive, which combined with a slight amount of moisture, causes a reaction on the blade?
Click to expand...
I think so! Might be a combination of variables. It doesn't matter to me, I was just surprised. Thanks
 
Interesting. Have had mine over a year with plenty of pocket carry and use. No rust anywhere.

There's not that much "spine" surface with the long swedge - ground to less than 1 mm.

Tip up right hand carry only. You'd think pulling/putting the knife out of pocket would wipe "clean" the spine. I'll keep an eye on mine.

MiniD.JPG
 
M390 is a tool steel, and not a stainless steel...it has higher corrosion resistance than several tool steels, and that is ALL it has...
 
mtngunr said:
M390 is a tool steel, and not a stainless steel...it has higher corrosion resistance than several tool steels, and that is ALL it has...
Click to expand...
M390 is a stainless steel with a Cr content of 20%, and strong carbide formers preventing chrome carbide formation which would hurt corrosion resistance.

If a piece of non-stainless steel becomes embedded in a piece of stainless, the stainless steel will rust because the non-stainless steel will break the oxide layer that makes the stainless steel stainless.
 
Stainless steel has carbon in it. During machining, microscopic particles of carbon either from the blade or from the tooling, are left on the surface. If the surface is not completely cleaned the carbon particles will rust. This is why quality boat fittings made of SS are bathed in a weak acid solution to dissolve the carbon particles.
 
mtngunr said:
M390 is a tool steel, and not a stainless steel...it has higher corrosion resistance than several tool steels, and that is ALL it has...
Click to expand...

Simply not true. The chemical compositions, which are very specific, determine the classification. All steel snobbery aside...

Bohler M390 is listed on the manufactures website as "ISOMATRIX PM Chromium Stainless Steel". Classified as "excellent" corrosion resistance due to high levels of chromium.

Similar in composition to Crucibles 20CV which has a greater corrosion resistance rating than 440C stainless steel.
 
Yeah I’m a little surprised as well. I’ve yet to have any staining happen to my M390 blades let alone rust. I imagine it could happen, it just never happened to me. Strange.
 
I purchased a new Elmax knife and after getting home noticed a few whispy superficial rust spots in the stonewash. They rubbed off with a bit of mineral oil and a quick pass if my fingernail. No issues since; non-issue to me.

Admittedly, it’s not The same steel, but I bring it up because some “charts” show it just behind M390 in corrosion resistance.
 
Thanks for all the feedback. I will keep my eye out if it happens again. I don't think it will because it was very small and like I said easy to rub off.
 
It is a cold work tool steel, and mold steel. High chromium does not stainless make.
https://www.bohler-edelstahl.com/en/M390.php

And real world use and test results, plus relative corrosion resistance from other makers of similar steels bears me out. Such as Crucible charts. You MUST take other alloying agents in to account, rather than only chromium contents.

You want to call it a stainless, be my guest, but you are misleading people every time you do.
 
Last edited:
OK - call it what you will. M390 is a stainless steel. It's 20% chromium.

I'm confident that Wikipedia, Simply Tool Steel, Blade HQ, USA Knife Maker, Barmond, USA Made Blade, Lamnia, DLT Trading, William Henry, Massdrop, German Knife Shop, GP Knives, and many other websites have their descriptions of M390 as "stainless" correct.
 
You must log in or register to reply here.
Back
Top