DLC and rust.

[Pelagic]

We're super mixed on this as a community. Some people swear by the corrosion resistance of DLC coating, and some people have reported issues with rust (and have provided proof).

Could it be that not all coatings are the same? Is there variation between the thickness of the coatings? Are all of spyderco's DLC blades coated by the same company? Does the steel being coated effect the effectiveness of the coating itself? Has there or will there be any CQI changes in regard to spyderco's DLC coating process or standards?

For me, lots of questions remain unanswered, but maybe together we can figure a few things out. Post your personal experiences with DLC here and please provide pictures. (postimageDOTorg works great)

Here is my experience: my first DLC coated blade was a Cold Steel Recon 1 in CTS XHP. It saw several months of carry on various rivers and in the ocean on tug boats and dredges. It did not rust through the DLC, but to be honest, the bevel didn't rust much either. I believe the bevel would have rusted more had I not sharpened it so frequently.

I also own a DLC coated Cold Steel AK—47 field knife in CPM 3V. This has mostly seen carry farther inland where rust isn't an issue. It saw about a week of carry on a dredge as well, and during that time acquired a few rust spots on the bevel. The DLC seemed impervious to rust.

The third was a Cold Steel Broken Skull, which saw several months of carry on the Savannah River and Charleston Harbor. The result was nearly identical to the Recon 1.

Maybe 30-40 days ago I got my hands on a knife that I value much more than most of my other knives (certainly much more than the aforementioned Cold Steel models), the St. Nick's Shaman exclusive in CPM 4V. I was not only happy about the model itself, but was ecstatic about the DLC coating providing some corrosion resistance to an otherwise perfect steel (imo). I left the harbor/ocean side of the industry in which I work and transferred to beaches. I was eager to use the model, but also wanted to take care of it, so I decided to carry it alongside my Broken Skull, which would handle hard use tasks or do anything that involved saltwater exposure. I remember making a post about comparing the effectiveness of the coatings. In just 3-4 days though, sand got on both knives and I decided not to carry the Shaman at work out of fear of getting sand in the pivot. I was bummed that I didn't get a chance to see how it performed and left it in my hotel room (I travel constantly). It wasn't until the next day that I noticed this:





I was surprised to see this amount of rust develop so quickly. I also have a DLC Manix 2 XL in s30v that saw a week of similar carry and has had zero rust issues. I am going to start carrying the Manix daily and see if any rust develops.

Share your experiences! St Nick's exclusive owners especially, have you seen any rust? What do you feel about DLC?

In the poll you can pick up to 2 choices.

[JuPaul]

I've never had dlc rust on me. But I also coat my dlc blades with mineral oil as I do my satin blades. And I don't live anywhere near an ocean. I have used my St. Nick's shaman outdoors, but not in the rain or when I was sweating a lot, so I don't have a good basis for comparison. Thanks to you sharing your experience, though, I know I need to be extra careful with that one. So sorry that happened to you!

Edit: I have seen minor rust spots on dlc non-stainless blades, but at the uncoated bevel only, though. Once on a spyderco 52100 manix, once on a non-spydie fixed blade.

[prndltech]

Where’s the option on the poll that says DLC wasn’t put on knives for the purpose of corrosion resistance?

It’s intent is for it being a non reflective finish. I’ve never seen DLC advertised in the description of a knife as being corrosion/rust resistant.

It may have a potential side effect of increase in corrosion resistance, but that’s going to be on a case by case, steel by steel basis I’d have a feeling.

[demoncase]

I've some experience with DLC coated blades and (in a more industrial context) DLC used for coating actuator bodies for aerospace use.
DLC gets selected to reduce friction, increase surface hardness and provide a very high temperature black colouration..... It's primary function is not rust prevention....

Look at this way: You'd oil a blued carbon steel firearm......why wouldn't you oil a DLC carbon steel knife?

There's a reason why stainless steel is useful :)

[The Meat man]

Did some cursory research into DLC coating and it is referred to as improving corrosion resistance.

I have to wonder if the thickness of the coating is the variable here. One website specifically mentioned its thicker DLC coating being a better corrosion barrier than standard-thickness DLC.

[Pelagic]

Where’s the option on the poll that says DLC wasn’t put on knives for the purpose of corrosion resistance?

That's common knowledge, this is more about personal experiences in regard to corrosion resistance since there are varying cases of such. I figured this goes without saying and wouldn't make for a good choice on a poll.

[demoncase]

Did some cursory research into DLC coating and it is referred to as improving corrosion resistance.

I have to wonder if the thickness of the coating is the variable here. One website specifically mentioned its thicker DLC coating being a better corrosion barrier than standard-thickness DLC.

It'll improve corrosion resistance- but it won't prevent corrosion.....That's the mindset to have.

Going from 'None' to 'Some".... 'Some" being a very long way from "100%"

[The Meat man]

Did some cursory research into DLC coating and it is referred to as improving corrosion resistance.

I have to wonder if the thickness of the coating is the variable here. One website specifically mentioned its thicker DLC coating being a better corrosion barrier than standard-thickness DLC.

It'll improve corrosion resistance- but it won't prevent corrosion.....That's the mindset to have.

Going from 'None' to 'Some".... 'Some" being a very long way from "100%"

That makes sense.
I'm curious now how thick Spyderco's DLC is.

[ladybug93]

i’ve seen this on a sog trident. i think it was dlc used on that knife, but i’m not sure. anyway, since the rust is under the coating, there’s no way to address it without removing the coating. this is why i don’t care for tool steel on folders and don’t understand why everyone here loves them so much. i do like dlc blades, but i probably wouldn’t buy one in a steel that is prone to rust because of the experience with the sog. i hope your experience with that shaman is not the same.

[vivi]

There is a big difference between coatings, even just looking at Spyderco.

Neither of my Perrin Bowies (Street Bowie and Street Beat) have coatings as durable as the DLC folders I've used.

The TiNi coating Pacific Salts and Szabo folders received does not seem to prevent corrosion as well as DLC, if at all, though its more durable than the Perrin coatings.

The coating on ESEE, BUSSE, TOPS etc. is not nearly as durable as DLC. It's thick and heavily textured, adding lots of resistance during a cut. It seems to prevent corrosion though.

I have really corrosive sweat, and I like to carry folders IWB during the summer because that's the most comfortable way to carry a pocket knife in running shorts. This exposes them to a lot of sweat.

Uncoated S30V shows corrosion after one summer day of IWB carry.

My DLC Para 2 was carried IWB for five summers and never showed corrosion on the blade. The (uncoated) liners were completely covered in rust.

My DLC Manix 2 XL has been carried IWB for a few summers. Zero corrosion, anywhere. It is the only non-salt folding knife to go at least s single summer with zero corrosion for me. It's done that for multiple years.

I've had DLC Militaries too, they performed just like the Para 2. Stop pin and liners rusted, blade stayed pristine.

The pictures of DLC Shamans and Millies with corrosion spots don't make sense to me. That's like seeing a picture of heavily corroded H1 based on what I've seen from DLC.

I did not oil any of the blades FYI. I don't find that to reliably prevent corrosion because slicing cardboard etc. rubs it off, so I don't bother.

[Evil D]

I really don't know what to vote, I've had I think 3 in DLC that I've actually used (one more is H1 and one has never been used or carried) and none of them rusted, but I also didn't throw them in the ocean. All I can say is none of them rusted in my pocket but uncoated M4 did. I don't know what you can get from comparing DLC S30V to uncoated M4, but that's all I can contribute to this one. I haven't had uncoated S30V rust in my pocket at the same job I did back when I had M4 rust on me, but I have had uncoated S90V spot rust in my pocket on a rainy summer day at my current job.

Bonus answer, I've had the edge bevel on my BK14 rust but the blade itself hasn't. Same goes for my ESEE Candiru, the edge and even the laser etched logo have rusted but the coating is still clean. I don't believe these knives use the same DLC coating that Spyderco use, in fact I'd say these coatings are nowhere near as high quality as the DLC Spyderco uses.

[Pelagic]

I wouldn't be surprised if we find that DLC does something like add a corrosion resistance point to a blades "score". Like if s30v is 8.5/10, DLC would make it 9.5—10/10, while 4V maybe a 2/10, and DLC makes it a 3/10. I realize that is a vastly oversimplified way of looking at it, but yeah.

Curious to see pics of DLC 4V or 52100 that have been subject to salt air or water.

[Sharp Guy]

I had to be honest and choose the last option...."I haven't exposed my knives to a corrosive environment yet". I have several knives with DLC and I certainly use them but it's not very humid where I'm now living (DFW area) compared to where I'm from (N. IL corn country). I'm not the outdoorsman that I used to be. So I don't really battle rust on my knives, tools, guns, etc like I used to. Back home I'd have tools rust after being in my toolbox or on my workbench in the garage after a short period of time. It doesn't seem to be the case where I'm at now. No issues with corrosion on any of my knives regardless of blade steel or if they're coated or not.

[Pelagic]

I had to be honest and choose the last option...."I haven't exposed my knives to a corrosive environment yet". I have several knives with DLC and I certainly use them but it's not very humid where I'm now living (DFW area) compared to where I'm from (N. IL corn country). I'm not the outdoorsman that I used to be. So I don't really battle rust on my knives, tools, guns, etc like I used to. Back home I'd have tools rust after being in my toolbox or on my workbench in the garage after a short period of time. It doesn't seem to be the case where I'm at now. No issues with corrosion on any of my knives regardless of blade steel or if they're coated or not.

That is awesome. I'd probably have 90% tool steels if I was in that situation!

[Bloke]

Hey Hitch, sorry to see your expensive new knife looking the way it does mate. Must be very disappointing to say the least, I'd reckon.

I've expressed my views on blade coatings in the past which didn't seem to go down to well with at least one avid supporter so I can't see the point of repeating them here. Suffice to say your experience only bolsters my views.

Hope you work out something to remedy the unfortunate situation.

[The Meat man]

Share your experiences! St Nick's exclusive owners especially, have you seen any rust? What do you feel about DLC?

I just pulled out my St Nick's Lil Native exclusive and sprinkled some water and salt on the blade. I'll report back tomorrow morning.

[TomAiello]

I think that the underlying steel is an important factor too.

Those XHP blades are going to resist rust better than 4v, with or without the DLC.

[vivi]

I'd think that if DLC makes steels impervious to rust, it'd work on any steel.

[Pelagic]

Share your experiences! St Nick's exclusive owners especially, have you seen any rust? What do you feel about DLC?

I just pulled out my St Nick's Lil Native exclusive and sprinkled some water and salt on the blade. I'll report back tomorrow morning.

Wow. Dedication right there!!!

I think that the underlying steel is an important factor too.

Those XHP blades are going to resist rust better than 4v, with or without the DLC.

Absolutely. I think the OP was the first time I forgot to mention this. But I will say I carried a DLC 3V knife for a week in salt air and it didn't rust through the DLC. That's twice the exposure that the Shaman received (regarding days in salt air) , but also, 3V is slightly more corrosion resistant than 4V. So many factors.

I'd think that if DLC makes steels impervious to rust, it'd work on any steel.

Definitely. Simple paint works this way, if you remove all rust, TRULY neutralize all the rust, or paint steel before it rusts, you can certainly keep the rust at bay for a long time. You'd think DLC was better than paint, and not just when it comes to abrasion resistance.

[northmanscall]

Here is my humble opinion on that subject.

Rust is iron oxide. Rust is prevented in stainless steels by forming chromium oxide on the surface. In both cases there is a metal reacting with the oxygen in the air.

DLC is almost pure carbon. It's reaction with the oxygen in the air will Form most likely carbondioxide. But that's not the case because the carbon is more stable in the dlc coating. There are DLC coatings with ppm of metals induced to enhance wear resistance. These metals Form carbides with the carbon in the coating. And carbides are really stable and don't "rust".

So my guess is it looks like there is a metal abrasion in the coating surface which contains iron and formed rust.

Or the coating is so thin that there are iron atoms diffunding through it. But that would mean we could see the grindlines and steelcolor because dlc can be applied quite thin.

But I guess maybe Larrin can say a word or two on this matter.

Greetings.