D2 and Corrosion Resistance

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FRNFanboy

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Aug 2, 2020
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Had an interesting experience recently, makes me thing we should have more respect for D2 in the area of corrosion resistance.

I’ve been playing around with forced patinas this weekend (yeah I’m that guy.) I took a Civivi D2 blade, and tried soaking it in hot vinegar for half an hour, 20 minutes wrapped in a paper towel soaked in vinegar, and wiped with lemon juice and let air dry for 20 minutes. Not even the slightest darkening of the steel, not so much as a spot or streak. I was very much surprised by this result, since some people talk about D2 as if it rusts if you even look at it funny.

I know D2 is semi-stainless, with the chromium in-solution slightly below the 11-12% required to be stainless, but this was impressive. Maybe D2 needs a little more respect as a workhorse steel?
 
In my relatively limited experience modern Chinese D2 is much more resistant to corrosion than American/European D2. Some of USA Ka-Bar D2 folders I had back 5+ years ago would take a patina very fast and would rust from condensation in the pocket if not cleaned and wiped every day. Meanwhile I've got Civvi and Artisan folders in D2 I go kayaking and hiking with and they've shown zero corrosion or patina.

I know the formula has a relatively large window of acceptable composition (looking for industrial D2 yields a ton of different comps) so it seems whatever they're doing is working pretty well.
 
I didn't think D2 patinas. I'm surprised something didn't happen though.
I wipe my knives down after I take them out of my pocket. None of my knives have rusted in the past 10 years. I have all kinds of budget steels, including D2.
 
M
mwhich50 said:
I didn't think D2 patinas. I'm surprised something didn't happen though.
I wipe my knives down after I take them out of my pocket. None of my knives have rusted in the past 10 years. I have all kinds of budget steels, including D2.
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I’m probably giving too much credence to the “D2 rusts like crazy” crowd. Am I wrong in thinking that the two are essentially the same process, just oxidation? I did get some other unexpected results, although as predicted, Maxamet patinas like crazy.
 
spoonrobot said:
In my relatively limited experience modern Chinese D2 is much more resistant to corrosion than American/European D2. Some of USA Ka-Bar D2 folders I had back 5+ years ago would take a patina very fast and would rust from condensation in the pocket if not cleaned and wiped every day. Meanwhile I've got Civvi and Artisan folders in D2 I go kayaking and hiking with and they've shown zero corrosion or patina.

I know the formula has a relatively large window of acceptable composition (looking for industrial D2 yields a ton of different comps) so it seems whatever they're doing is working pretty well.
Click to expand...
Interesting... is it the actual composition of the steel, or maybe the heat treat?
 
FRNFanboy said:
M


I’m probably giving too much credence to the “D2 rusts like crazy” crowd. Am I wrong in thinking that the two are essentially the same process, just oxidation? I did get some other unexpected results, although as predicted, Maxamet patinas like crazy.
Click to expand...
I definitely think that there are two different processes going on, but I don't know much about it. I am not a patina fan.
 
I have an Ontario RAT 1 in D2 that picked up a splotchy patina within an hour of using it to cut apart some barbecue-sauce covered ribs, so it's definitely possible.
 
Yalius said:
I have an Ontario RAT 1 in D2 that picked up a splotchy patina within an hour of using it to cut apart some barbecue-sauce covered ribs, so it's definitely possible.
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I know some folks use mustard to force a patina, so maybe the condiment method is required!
 
I like to force patina on my kitchen knives, and so for none have resisted the citric acid. You can buy everywhere as its basically dry lemon juice. You might wanna try with that.
 
Spelling in title corrected. There are limits as to what I can withstand.

D2 won't "patina", form a uniform coverage of surface oxidation. Surface oxidation is just cosmetic.
But it does form pitting corrosion, and pitting is what leads to actual damage of the steel.

That being said, generations of outdoorsmen used carbon steel blades successfully. So there's nothing that says that a blade must be stainless to be useful.

But I definitely don't consider D2 stainless. I have too many D2 blades with polka dots of corrosion on them.
 
It’s not necessarily the shortage of chromium that makes D2 non-stainless. If it had 13% Cr it still would be non-stainless. There are stainless steels with 11-12% Cr just like D2. The high carbon in D2 means that a lot of chromium forms carbides, where it is no longer “in solution” to form a chromium oxide layer at the surface. There isn’t really a fixed line between stainless and non-stainless. Typically more chromium in solution means better corrosion resistance. https://knifesteelnerds.com/2018/06/11/how-much-more-chromium-does-d2-need-to-be-stainless/
 
I've given a D2 blade a nearly black finish by etching with ferric chloride and then applying a cold bluing solution. I am not sure it that would constitute a 'patina' or not.
 
I have seen a little patina on a D2 blade that was in my pocket when I was harvesting grapes on a really hot day and had some grapes end up squashed in my pocket on the knife. But more commonly with D2 I have seen pitting.
 
Most of the D2 I’ve used from varying makers mostly just get pepper spots (red or black) after leaving them wet for too long. Polishes off really easy though.

The toothy edge D2 seems to like is awesome for softer media’s like meat or food.
 
D2 is downright awesome for my use. Stays sharp for a reasonable time and does not take much to bring back. I have a Ontario Rat 1 on hand for kitchen duties is use most everyday. I wash it in the sink and put it up wet. In a couple weeks some rusting or discoloration is evident around the pivot area. A 10 minute tear down and the oxidation is gone...... I love a lot of steels but would choose D2 99% of the time for my needs, That includes camping as well. I do love the properties of this metallurgy. TD
 
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D2 is just like 8Cr in that if it's done right, it's great. (Though D2 is harder when done right)

I've never had D2 rust on me, but I've had some soft D2 out of China. It acted like AUS-8 or 420HC.
 
I have read that both Friction Forged D-2 and CPM D-2 are more resistant to corrosion than conventional D-2.
 
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