M4 - Is it a ‘Rust Magnet’..?

jnevill said:
Not to thread crap too hard, but how does M4 compare to M390? I love my M390 Kershaw....
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I have no M390 knives therefore no personal experience.
Maybe someone else will chime in here.
iirc @Ankerson has a thread somewhere about all the supersteels that can shine some light on your question, but my search foo is no good atm.
 
jnevill said:
Not to thread crap too hard, but how does M4 compare to M390? I love my M390 Kershaw....
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I’ve had two M4 knives and two M390 knives. Let me preface by saying I like M4 better.

Ive found m4 takes a “crisper” edge if that makes sense. It also will keep it longer than is reasonable—the only time my pm2 has gotten fully dull was when I used it to cut up fiberglass insulation.

For rust resistance, m390 is by far better, but I haven’t had any major problems with m4, so to me this is moot. I used to have a mantra which I sold to a buddy last year. He used it to field dress a deer and left it in a sink full of soapy water for a week to clean it. It developed orange rust then, but not even on the whole blade because there was some patina on it.

Both of my m390 knives seem to roll the edge much easier than I would like, although it could definitely be my lack of sharpening skills and me leaving a burr.

M4 is really tough in a folder, not like I would pry with it but it makes it harder to break the tip. My m390 knives are probably just as tough, but I’m hesitant to test it.

Those are my opinions of the steels, hope it helps
 
Ok so Satin m4 to this. I stuck it in a potato and let it dry for a few hours. sliced some oranges up with it let the juics dry on it. Then wiped apple cider vinegar on it and let it dry about 6 times. Then submerged the whole blade in apple cider vinegar for close to 6 hours. Here is the result. I'm really happy with it and have prayed it with some Edci to stop any further patina.
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My blades in M4 have been plenty resistant to rust, but my work knife did develop surface rust quickly when I carried it in my pocket one morning while I was working in the yard and sweating a lot.
 
Mine picked up a few spots of surface rust, but that is on me. I didn't realize M4 would rust and didn't wipe it down after use. Even with that, they are very minor spots.
 
Stumpy72 said:
Thanks. I can see that one day I’ll have to get a cheap non-stainless knife or two to experiment with. Just out of curiosity... Does a forced patina have any effect on the likelihood of future rust?
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While a forced patina is not rust proofing anything it diminish the development of it. Although rusting is generally a negative aspect of steel, a particular form of rusting, known as "stable rust," causes the object to have a thin coating of rust over the top, and if kept in low relative humidity, makes the "stable" layer protective to the iron below. coating the layer with oil, wax or paraffin will help stabilize the patina and slow down progression of rust.
 
SteelJunkee said:
While a forced patina is not rust proofing anything it diminish the development of it. Although rusting is generally a negative aspect of steel, a particular form of rusting, known as "stable rust," causes the object to have a thin coating of rust over the top, and if kept in low relative humidity, makes the "stable" layer protective to the iron below. coating the layer with oil, wax or paraffin will help stabilize the patina and slow down progression of rust.
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OK. Is there a specific way to lay on a layer of “stable rust” or is just playing with one of the forced patina expeditors mentioned above good enough?
 
Stumpy72 said:
OK. Is there a specific way to lay on a layer of “stable rust” or is just playing with one of the forced patina expeditors mentioned above good enough?
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It will be only one, you will need to repeat the process a couple of times to get a durable layer, the first dip will almost all rub off with a cloth, after repeating the process 2-3-4 time it will start to be more etched in the steel more difficult to rub off.

What I do is, 3 to 4 dip, each with new and very hot vinegar, leave soaking until it stops bubbling. After rinse and oil or wax. It will give you a uniform dark grey patina that is not really pleasant to look but it will become beautiful with use. keep wiping your knife after uses and regular oiling or waxing of the blade will help a lot. But after I did that my carbon steel knives nearly stopped developing the filthy orange rust in rainy conditions preventing pitting and total aggravation etc.

rustyknife.jpg



I believe that M4 will also have a good response to vinegar forced patina.
 
I had a custom camp knife in CPM M4 acid washed and it's held up superbly. My other knives is M4 do well enough. My carbon steels do fine with a wipe of mineral oil every week or so or after working with acidic stuff like food (usually my 1095 trapper or moose knives). The acid wash, which is just a heavy patina really, has added nearly the level of rust/stain resistance of a satin finish D2. Shades may change a bit but I don't get rust unless I neglect it badly or am in a situation where it's going to be a bit before I can wash it.

New
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After about a year and I'll say moderate use. It's been sharpened up once or twice at least... takes a long time to get it that far though. (Didn't have any good photos if it alone)
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M4 seems to be far more rust resistant than 52100 which seems to rust faster than anything I've seen including more basic carbon steels like 1075 and 1095.
As a comparison, 52100 layers of patina. I oil this after every trip out that it gets used, it sees a lot of use. I've never oiled the M4 blade above, I just keep an eye on it to see how much it can take before it starts to show any spots.
GVlnjvMl.jpg
 
I ve decided not to carry a non stainless blade as my outdoor work knife. I tried using my GB1 for work outdoors, sometimes near the ocean. In hot weather I would get sweat on the knife. I would rinse the knife off in fresh water and wipe it off every night. Maybe apply a little WD40 every week or two. I still got rust spots which had to be lightly sanded out. Too bad, because I really like the edge holding, and the apparent toughness of of that blade. And I liked the knife in general. But I have to have more corrosion resistance.
 
whp said:
I ve decided not to carry a non stainless blade as my outdoor work knife. I tried using my GB1 for work outdoors, sometimes near the ocean. In hot weather I would get sweat on the knife. I would rinse the knife off in fresh water and wipe it off every night. Maybe apply a little WD40 every week or two. I still got rust spots which had to be lightly sanded out. Too bad, because I really like the edge holding, and the apparent toughness of of that blade. And I liked the knife in general. But I have to have more corrosion resistance.
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Have you tried... Letting a patina develop or... Force it, and add a good Hot paraffin bath to stabilize that... (I know oil is mostly used but it does not last wax does last, Food grade paraffin does much better :)), swipe, let cool, buff smooth and use. I stopped a Glock from rusting with that, it looks Beautiful now. And it`s the kind of knife that waaaant`s to rust, but it`s the most beatable/weight ratio i've ever encountered, and.

Since I did it, it stopped singing. "I can't stand the rain..."

But... of course it is not eternal :( you will have to "Take care of it" but Waxing superseded oiling for me ages ago (Well since I got some swords ending in my hand) and I could really tell that waxed blade conserves longer, even the really polished ones...

And maintenance is a breeze, just have to hum, hum... For a Field knife... not an actual sword, but close... Heat the blade with a paint gun and rub a block of Paraffin on it, swipe and use... Shhhhh don`t tell anyone. It`s AWESOME for sheaths and wooden handle too, as an Opinel fan I can tell, you can water proof jeans with that...
 
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