Expectations around CPM-3v and corrosion resistance

J

jaredw

Joined
May 30, 2024
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Hello,
I'm new here so apologies if this is the wrong section.

I recently picked up a knife in CPM-3V, a fixed blade, NOT a CPK. Now, it has rusted twice and pitted pretty decently once. The first time I left it soaking wet for about 36 hours, I had been wading through water and it was legit soaked. The knife had enough rust and pitting that I needed to go to almost 100 grit sandpaper to remove the browning on pits on the spine, the rust on the edges came off at about 600 grit.

Ok, I left it in water, that one seems reasonable?

Round 2, 1 hour in the rain on my hip, minor wetting, pulled immediately, the knife had browning after a limited time and minimal exposure to water. I had oiled it before hiking with it the second time.

Question, is this metal just not really meant for carry in situations where it might get wet?

If yes I might go try a magnacut version if it becomes available.

Full disclosure, after the first time I polished the original factory coat off and put a shine on the blade.
 
jaredw said:
Hello,
I'm new here so apologies if this is the wrong section.

I recently picked up a knife in CPM-3V, a fixed blade, NOT a CPK. Now, it has rusted twice and pitted pretty decently once. The first time I left it soaking wet for about 36 hours, I had been wading through water and it was legit soaked. The knife had enough rust and pitting that I needed to go to almost 100 grit sandpaper to remove the browning on pits on the spine, the rust on the edges came off at about 600 grit.

Ok, I left it in water, that one seems reasonable?

Round 2, 1 hour in the rain on my hip, minor wetting, pulled immediately, the knife had browning after a limited time and minimal exposure to water. I had oiled it before hiking with it the second time.

Question, is this metal just not really meant for carry in situations where it might get wet?

If yes I might go try a magnacut version if it becomes available.

Full disclosure, after the first time I polished the original factory coat off and put a shine on the blade.
Click to expand...

If you are willing, try soaking it in vinegar, or coffee for a bit.... Try a few mins at a time.... It won't completely protect it, but it will slow things down a bit.

I haven't done it with My 3v, but I've done it with other steels that are even more prone to rusting.
 
I haven't rusted 3v yet, but I also haven't had a knife in it wet yet either. the 36 hour doesn't surprise me as I can make aus8 rust spot in a sweat soaked pocket in a hour or less.

the 1 hour wet and dried..surprises me a bit...leather sheath or kydex stayed wet inside or no?

browned meaning just colored stained? did red rust happen or just the coloring on the blade?
 
jbmonkey said:
I haven't rusted 3v yet, but I also haven't had a knife in it wet yet either. the 36 hour doesn't surprise me as I can make aus8 rust spot in a sweat soaked pocket in a hour or less.

the 1 hour wet and dried..surprises me a bit...leather sheath or kydex stayed wet inside or no?

browned meaning just colored stained? did red rust happen or just the coloring on the blade?
Click to expand...
It was in kydex, it stayed wet inside, purely my fault, I just pulled the whole thing out and tossed it in a backpack. Full red rust and pitting the first time. The second time it was spotting but still took 1500 grit paper to get off.

I etched the part of the blade that is in the micarta in ferric acid after the fact and it blackens up really nicely. I was thinking of etching the blade too but its goes very dark and I'm not sure about the aesthetics.
 
Vaseline is a cheap and very effective rust preventive -- also food safe. Living in a relatively dry climate, I haven't had any problems with my Puukko 200.
 
With many high alloy steels there can be a big difference in field corrosion if the heat treat was a standard industry high temperature temper instead of the cutlery recipe of cryo and low temperature temper.

For your situation I have found lip chap to work very well to protect low alloy steels from rust. If you get in the habit of wiping blade down after use or and before storage you won't have an issue.
 
Thanks. I’ll go with those suggestions. I’d just been using some lightweight oil. I find the heat treatment stuff fascinating.
 
I've had 3V rust also on a CPK. It happens. Since then, I use froglube under the scales.

Wasn't as bad as your Round 2, though, that sounds suspicious. You sure it is 3V ? Some manufacturers are known to use a steel different from what they claim. What knife exactly ?

BTW, you don't need to wait for Mangnacut if AEB-L is available - very cool steel for fixed blades.
 
Pretty sure it’s 3v. I left out the name to avoid looking like manufacturer bashing. I did leave it sit for more than a day in rain and probable sweat.
 
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