DLC coating rust & corrosion resistance question..

four_shore

four_shore

Joined
Oct 21, 2010
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does anybody know if spydercos DLC coating helps to prevent rust/corrosion, or is it strictly to make the blade non reflective and less prone to scratches?
any information on this topic would be very much appreciated.

thanks
 
I think only one company does DLC coatings and if its like the knife I had from another company, the rust will 'grow' right through the coating. But it rubbed right off and you would have no idea there had been rust. I'm sure if it rusts too much it will pit and the coating will come off eventually.

Another thing to think about is there have been hardness tests done and some DLC coated blades have been softer than uncoated versions.
 
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DLC is for light discipline, not corrosion resistance. This has been discussed before by the Spyderco crew. If you did a search, I'm sure you would find the threads.
 
FlaMtnBkr said:
I think only one company does DLC coatings and if its like the knife I had from another company, the rust will 'grow' right through the coating. But it rubbed right off and you would have no idea there had been rust. I'm sure if it rusts too much it will pit and the coating will come off eventually.

Another thing to think about is there have been hardness tests done and some DLC coated blades have been softer than uncoated versions.
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are you talking about the ritter grip M4? that's weird but true. they invented the coating that patinas, fun.

do you have any link to the hardness info ? that's the second time i read that and IIRC on the previous post sal commented himself that he wasn't aware of this and it was less than likely ...

my first milie is a black one and even if i don't use it anymore i've not noticed any difference in edge holding or sharpening feel.
 
I don't have a link and would have to search for it. I will look because if Sal has said it isn't an issue I will take note.

I don't remember which knife it was off the top of my head. I will have to look through my knife box but I don't have many DLC knives so it could have been the M4 Ritter.
 
RevDevil said:
DLC is for light discipline, not corrosion resistance. This has been discussed before by the Spyderco crew. If you did a search, I'm sure you would find the threads.
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I didn't say it was for corrosion resistance, I simply asked if it helps. I've also done some research with really no solid answer on the subject.
 
like i said above, i can't speak for milie as it's S30V and is not that much subject to rust but my DLC ritter in M4 steel will definitely "rust" under the coating.

their coating looks very different though, the ritter has a very thin and glossy coating, it's so thin you can see the grind lines. the milie doesn't show the finish underneath so i assume it's "thicker", and matte black.

anyway you got two sources quoting spyderco so i think the info is solid.
 
four_shore said:
does anybody know if spydercos DLC coating helps to prevent rust/corrosion, or is it strictly to make the blade non reflective and less prone to scratches?
any information on this topic would be very much appreciated.

thanks
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No, it does not help. If the steel is stainless that is what helps.
 
Well it looks like I was wrong and there is more than one company that does the coating. I thought I had read there was only one company that did it but maybe there is only one company that makes the material that is deposited. I did a search and nothing I found said anything about corrosion resistance and I'm sure the companies would advertise it if it did. It looks like the main function is increasing wear resistance.
 
Thanks for your response. I figured any time a blade is coated that alone would unintentionally help prevent corrosion (regardless of it's main function). I noticed that when the DLC on my para 2 gets wet, it dries in seconds...almost absorbs into the blade. That experience led to the posting of this thread...
 
four_shore said:
And you know this how?
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It has been posted by Sal and crew many times on the Spyderco factory forum. This question pops up fairly often on that forum, and each time the quote from TazKristi is posted.


The DLC does not help with corrosion at all. If your blade is going to rust then it will rust right through the DLC. Cleanup is the same, you can remove the rust without altering the coating at all.
 
How I see a dlc coat is better than having no coating at all.Sure it will rust but the rust will gradually come off.Beats missing a chunk of steel from a blade though.
 
I'm not sure I follow. If it rusts it sounds like it will do it whether it is DLC coated or not. If it rusts so much that it pits, then a couple micron thick coating isn't going to stop the pitting. The coating will just fall off with the rusted steel. I assume the missing a chunk of steel comment is about blade pitting? If so I don't think DLC will stop that.
 
pwet said:
like i said above, i can't speak for milie as it's S30V and is not that much subject to rust but my DLC ritter in M4 steel will definitely "rust" under the coating.

their coating looks very different though, the ritter has a very thin and glossy coating, it's so thin you can see the grind lines. the milie doesn't show the finish underneath so i assume it's "thicker", and matte black.

anyway you got two sources quoting spyderco so i think the info is solid.
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DLC, Boron Nitride, and Titanium Nitride finishes are so thin that they don't have much bearing on the "flatness" of the finish. They take on the appearance of the surface before coating. If you coat a polished blade it will be glossy, if you coat a bead blasted blade, it will be matte, and if you coat a coarse sandblasted blade, it'll be a very flat and rough finish. I'm a bit surprised that the DLC coated stuff isn't more rust resistant, I know titanium nitride doesn't do much unless the steel has additional anti-corrosive layers of plating, but IIRC the DLC surface was supposed to be non-porous enough that it wouldn't allow water vapor to creep through the coating and cause rust.
 
razorburn said:
How I see a dlc coat is better than having no coating at all.Sure it will rust but the rust will gradually come off.Beats missing a chunk of steel from a blade though.
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Nope. The blade will still pit.

Let's say it again, having a DLC coating is like having no coating at all. (as far as rust resistance is concerned)
 
razorburn said:
How I see a dlc coat is better than having no coating at all.Sure it will rust but the rust will gradually come off.Beats missing a chunk of steel from a blade though.
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Missing chunks of steel?
Really?

yoda4561 said:
DLC, Boron Nitride, and Titanium Nitride finishes are so thin that they don't have much bearing on the "flatness" of the finish. They take on the appearance of the surface before coating. If you coat a polished blade it will be glossy, if you coat a bead blasted blade, it will be matte, and if you coat a coarse sandblasted blade, it'll be a very flat and rough finish. I'm a bit surprised that the DLC coated stuff isn't more rust resistant, I know titanium nitride doesn't do much unless the steel has additional anti-corrosive layers of plating, but IIRC the DLC surface was supposed to be non-porous enough that it wouldn't allow water vapor to creep through the coating and cause rust.
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It has nothing to do with porosity, and everything to do with depleting free chromium. Stainless steel will actually become less resistant to corrosion if it is nitride coated. Free chromium will bond with nitrogen to form chromium nitride(CrN), rather than form a corrosion-resistant passivation layer.
 
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