K390 - less stain resistant than people claim.

L

LostCause

Joined
Apr 1, 2022
Messages
840
I had K390 Endura.
I sold it.

About 1 year later I got K390 Delica...
Also got rid of it and got Matriarch 2 Emerson instead.

Why?
No matter what I did, it'd not stop rusting

Nothing short of drenching it in oil would help. Even when I'd oil it generously - it'd just oil my pocket, and eventually form spots on places oil rubbed off or near spydie hole after I'd use it.
Or if I'd cut something - those places would develop corrosion unless I spread oil from rest of the blade to those parts.
I tried with patina too.
Area near spydie hole would develop corrosion most readily in both cases.

I even had AUS10 rust on me in the past (Cold Steel Voyager), but it just rubbed off easily, and I sold the knife after a whole. I know that something being callled stainless doesn't mean it's not ever going to rust. But it is the fact that people really spoke so good about K390 being more stainless than expected, and I'm really not feeling or seeing it.

I know it's summer, it's really humid, and some sweat will be in any pocket. But I also watched and read some reviews and they all claim that light coat of oil at best is all you need and you'll be fine. My experience is opposite.

CPM-3V AK47 knife that I have for years has never rusted on me on the blade. But I did had it rust on exposed parts of the tang on the handle. I never oil it, and it's a fixed blade so it's fine. My fixed blades are all non-stainless and I'm OK with it. But in a folder... becoming gritty because of rust inside... that's last thing I want.

K390 Spyderco knives are really great performers... but don't expect them not to rust at summer, and take all reviews with grain of salt.

My current carry:
ESEE Candiru and Spyderco Matriarch.

Candiru only ever had some corrosion on edge,which would get taken out with sharpening, and there's some staining on places where coating is worn off. It seems that sheath does make the difference. But, I really don't care about it on a fixed blade. Matriarch however has 0 issues, but it is coated VG-10 so I'm not expecting them either.

I want something I can use, wipe off, put back in my pocket and forget about. Not something I have to get out of my way to prevent from rusting just from being carried. Or to have my pockets drenched in oil because of the blade that always has to be oiled being there. So, K390 is not something I'm looking for in a folder. I'd however like to get a K390 fixed blade down the road.
 
Have you tried a dry lube? I wipe down every new blade I get (carbon or stainless) with Sentry Solutions Tuf Cloth. Let it dry and it’s good for months. After a knife gets used, I just wipe down the blade with a silicone cloth. If it’s a blade that is touching food, I just apply a very thin layer of mineral oil instead. Between the dry lube and the silicone (or mineral oil), no rust whatsoever
 
rlewpolar said:
Have you tried a dry lube? I wipe down every new blade I get (carbon or stainless) with Sentry Solutions Tuf Cloth. Let it dry and it’s good for months. After a knife gets used, I just wipe down the blade with a silicone cloth. If it’s a blade that is touching food, I just apply a very thin layer of mineral oil instead. Between the dry lube and the silicone (or mineral oil), no rust whatsoever
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I used it on food fairly often. I used mineral oil too, but I still had rust issues. It would rust no matter what I did. It'd either be constantly babied or it'd rust.

My current Candiru and Matriarch combo works for me, but still I find it odd everyone praised K390 for corrosion resistance when my experience has been completely opposite. Both, 3V and D2 are leagues ahead of it in corrosion resistance. I admit 1095 rusts when you look at it, but sheath does it's job keeping it away from salty sweat and protecting oil from rubbing off on clothes, plus the coating.

But still it boggles my mind that I got rid of K390 because of corrosion issues and yet one of steels I now carry is 1095. I know, fixed and folders are oranges and apples, but I really wanted to love K390. I tried with K390 twice and don't think I'll give it another shot... maybe for a fixed blade eventually.
 
LostCause said:
It would rust no matter what I did. It'd either be constantly babied or it'd rust.
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This. I have many other steels with a comparable amount of chrome that keep perfectly clean in my household also with food prep, like 10V, M4, A2, etc, but K390 (in my case in a P4) is basically useless.
 
You have to force a patina on K390 to keep it from corroding any further. If you’re wanting a beautiful shiny blade in a knife, K390 is not for you. I have several in K390 and I haven’t seen much after a forced apple cider vinegar dip.
 
On the bright side, it is easy to remove the rust. I rub the blade down with a scotch-brite sponge and a drop of oil, then wipe the rusty "slurry" away. It will never be spotless, but my K390 knives are all users/beaters, so it's fine. Another possibility would be to force patina on it. IDK what is the best way to do it on K390 though.
 
LostCause said:
I used it on food fairly often. I used mineral oil too, but I still had rust issues. It would rust no matter what I did. It'd either be constantly babied or it'd rust.

My current Candiru and Matriarch combo works for me, but still I find it odd everyone praised K390 for corrosion resistance when my experience has been completely opposite. Both, 3V and D2 are leagues ahead of it in corrosion resistance. I admit 1095 rusts when you look at it, but sheath does it's job keeping it away from salty sweat and protecting oil from rubbing off on clothes, plus the coating.

But still it boggles my mind that I got rid of K390 because of corrosion issues and yet one of steels I now carry is 1095. I know, fixed and folders are oranges and apples, but I really wanted to love K390. I tried with K390 twice and don't think I'll give it another shot... maybe for a fixed blade eventually.
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I have a few Lionsteel fixed blades in K390 (M1, M2M and M4, top to bottom). Very well done knives if you are looking for good fixed blades in this steel. The M2M is a particular favorite of mine. Stock photos

Edit: Oops, these knives are M390. All the more reason to consider M390 as this is the stainless version of K390. Now I’m wondering if the OP got the two confused and heard that M390 was stain resistant and confused it with K390 🤔

Here is a short article comparing both:


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24B47C62-2DEC-443B-B279-D10D4097F605.jpeg
 
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ktataragasi said:
Rust issues are very personal. I have carried 1095, c75, k390, Maxamet and Rex 45 in the southern heat and humidity with zero rust. I never oil my blades. Some people just sweat differently.
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I have no issues with fixed blades, but seem to have issues with folders.

Other thing is - I usually use my blades on food. That often contributes to corrosion issues.

And finally, I also get caught up in the rain from time to time. My phone is IP68 so it's not an issue for that at least.
 
LostCause said:
I have no issues with fixed blades, but seem to have issues with folders.

Other thing is - I usually use my blades on food. That often contributes to corrosion issues.

And finally, I also get caught up in the rain from time to time. My phone is IP68 so it's not an issue for that at least.
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I use mine on food all the time. Yes they get a patina but never rust.

IMG_20230620_211801_660.jpg20230524_175053.jpg20221211_110848.jpg20210217_090613.jpg
 
Yeah, like's been said here above, K390 isn't the steel to go with if you need good corrosion resistance and don't want the blade to form a patina. It's all about compromise. It's a great steel for performance though if you don't mind some patina, and possibly some rust spots if you have corrosion sweat or different weather conditions. I have a little Pena Slipjoint in K390 that I've never really used because it was a low number limited edition and I don't want to patina it up just yet. However I did carry it in a slip one day and noticed a few small spots of patina just from playing with it and not actually cutting anything.
 
LimpCroissant said:
Yeah, like's been said here above, K390 isn't the steel to go with if you need good corrosion resistance and don't want the blade to form a patina. It's all about compromise. It's a great steel for performance though if you don't mind some patina, and possibly some rust spots if you have corrosion sweat or different weather conditions. I have a little Pena Slipjoint in K390 that I've never really used because it was a low number limited edition and I don't want to patina it up just yet. However I did carry it in a slip one day and noticed a few small spots of patina just from playing with it and not actually cutting anything.
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I don't mind patina. But I do mind that orange rust that forms. And having it rust that way from just carry alone is annoying. And knife I'm not carrying is useless to me.
 
LostCause said:
I'll just keep rocking the Candiru and Matriarch combo. I kinda gave up on so called super steels as I got no real difference with carrying K390 over 1095. Both can go more than a day without sharpening and 1095 is super easy to touch up.
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I guess you could say k390 is a.... Lost Cause.....

Yeah man do what is best for you.

For what it's worth I use a medium spyderco ceramic to touch up all of my blades and it does great.
 
LostCause said:
I don't mind patina. But I do mind that orange rust that forms. And having it rust that way from just carry alone is annoying. And knife I'm not carrying is useless to me.
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Yeah rust is no bueno. I'd just stay away from K390 as you're thinking since it doesn't suit you. I'm a driver for a living and wear cargo shorts during the summer, so I usually carry 3 folders just for the hell of it. I carry one in my front pocket as my main user folder, one in a cargo pocket as a real hard use one for nasty jobs I don't want to use my nicer main folder for, and that leaves one pocket for whatever other knife I feel like carrying that day. I put that K390 Pena slipjoint in a pouch there that day because I felt bad about it never getting used, however I was always unsure if I wanted to trade it for something else, so have always kept it in tip top shape.
 
ktataragasi said:
Rust issues are very personal. I have carried 1095, c75, k390, Maxamet and Rex 45 in the southern heat and humidity with zero rust. I never oil my blades. Some people just sweat differently.
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Im in central Alabama and this had also been my experience. Rarely if ever oil anything.

My Stretch 2 in k390 is one of my most used beater knives. Sure, it has some patina, but I don't think I've ever found any actual rust on it. Thinking back, I've honestly had more rust issues with steels like AUS-8 and, here lately 14c28n, than I have with k390, Maxamet, and Cruwear..

Different strokes for different folks I guess.
 
Might want to consider something in LC200n steel . If you can rust that steel under any conditions, I’ll be impressed. Spyderco makes some nice knives in that steel. The Spydiechef (folder) and the Waterway (fixed blade) come to mind
 
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