M4 steel

Baller

Baller

Joined
May 4, 2015
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I plan on picking up the Spyderco pm2 in M4 steel. I have no experience with this steel but understand that it isn't very corrosion resistant. Will it rust even if kept in storage with no use? How often should the blade be oiled?
 
M4 is not very corrosion resistant compared to stainless steels, but I haven't seen much and never experienced any issues with random stopping or rusting on my GB while I had it. If you are super concerned with corrosion, it does take a patina rather easily, and with a patina and regular care you should see next to no rust if any.
 
I've had CPM-M4 from a couple of different knife makers. I haven't had any corrosion issues with it. I do put a light coat of mineral oil on my non-SS blades when they first arrive, but that's about it. I just keep them dry and store them out of the sheath. I'm in north Georgia and that seems to work well for me with M4.
 
My Benchmade 810 is M4 has been a great knife. Edge retention is amazing. It will not rust in storage, but I have had some rust on the uncoated portion of the edge when I have worked in the rain or sweated on it a lot. A little stropping has always taken it off.
 
Marine Tuff Glide is a tool steel's best friend. Inexpensive and incredibly effective at preventing corrosion.
 
M4 is not corrosion proof but it's not corrosion prone either. If you use it a lot, it will form a patina (stain) but it won't rust if you clean it after use and then let it dry. I've carried and lightly used a Spyderco Gayle Bradley for a year or so and never saw any rust on the blade yet I never used any oil whatsoever and I cleaned it mostly by just rinsing it off with tap water and shaking it dry. It's hot and humid where I live but I don't live near an ocean. If used more heavily and used it in a corrosive environment, more attention to cleaning and then using a little oil would be a good regimen. As for rusting during storage, well it would depend on whether or not you washed and dried it, wiped with a little light machine oil and stored it in a relatively dry, non-corrosive environment.
 
My Manix 2 M4 came with a patina on it and has rusted a bit if not kept perfectly clean.
 
Comeuppance said:
Marine Tuff Glide is a tool steel's best friend. Inexpensive and incredibly effective at preventing corrosion.
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Yep!

I've never used the "Marine" formula, but their regular formula has served me well. I use it on all of my knives.

Regarding M4, I never had an issue with rust on my Gayle Bradley folder. I actually forced a patina on it, and it took forever!
 
Comeuppance said:
Marine Tuff Glide is a tool steel's best friend. Inexpensive and incredibly effective at preventing corrosion.
Click to expand...
+1
I use the standard TufGlide/TufCloth on all my carbon steel knives as well as my firearms and I've never had any rust issues.
 
CPM-M4 will corrode without proper care. The corrosion resistance is just a little better than steel like 1095 from my experience.
 
Baller said:
I plan on picking up the Spyderco pm2 in M4 steel.
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lol, tell me more about this "plan"...
Does it involve going on BHQs New Arrivals page every day, several times per day between now and Christmas, and checking for it? Because I think that's about the only plan available, and it's everyone else's plan too.
Maybe by "planning" you meant "hoping"? :p
 
I went swimming in the Atlantic Ocean for around 2 hours with a m4 knife and it didn't rust. However I did rinse it when I got home.
 
CPM-M4 is awesome steel, but if corrosion resistance is an issue, there are better steels. When M4 rusts, it pits, which is the worst kind of corrosion. I live in a rainforest, and I have a number of blades -- including some of my favorites -- in M4, but I have to make sure I take care of them.

As an alternative in a stainless steel, when corrosion resistance is important, M-390 is great if wear resistance is the key attribute. Elmax is great if toughness is the key attribute.
 
It depends on where you are storing it. If you live in a very humid environment then it will eventually show some corrosion if left dirty or unoiled. As mentioned earlier, tuff glide is a good option. I live in the tropics and have numerous knives in m4. They are all users and all have some patina but I keep them clean and don't have any corrosion issues.
 
All my knives get cleaned of anything corrosive and then renn waxed before storage. I have no problems with any knives that way no matter the steel as long as I don't have any leaks on them or store them in holsters or sheathes . Leather especially. Stainless steel gets the same treatment as carbon/alloy steels because they rust too. Except H1 anyways.

Joe
 
Twindog said:
When M4 rusts, it pits, which is the worst kind of corrosion.
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I've experienced this also with cpm m4, very tiny pin hole pits, in a 10 hour period. It's the only type hss blade I've had this happen even though my others (except the newly acquired hap40) have been used in harsher more corrosive environments for longer periods of time.
 
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