How can you tell if black dlc blades are corroding?

[Cave_Hermit]

Hey guys how can you tell if a pvd or dlc coated blade is corroding? My para 2 (black coating) has been my workhorse and I live next to the beach and thought it would have some sort of corrosion by now even though it is stainless. Apart from rust seen on the cutting edge how could you tell? Thanks.

[vivi]

It won't. I am incredibly tough on the corrosion resistance of things and I EDC'done for years. Carried it on an 800 mile bike tour too. Rusted the stop pin, lock and liner real bad, but the blade was pristine. The DLC Para 2 is the knife that made me fall in love with DLC for its amazing corrosion resistance.

It might sound weird, but smelling the folder is a good way to detect internal rust. My Police 3 looked fine from the outside, but the inside was coated in rust. Liners on both sides, pivot, lock bar, etc. Found out by the smell. It was so strong I could tell from arms length away.

If nothing else you can always open it up and check. I try to avoid doing that any more than I need because it can be easy to strip screws.

[Joey]

It won't. I am incredibly tough on the corrosion resistance of things and I EDC'done for years. Carried it on an 800 mile bike tour too. Rusted the stop pin, lock and liner real bad, but the blade was pristine. The DLC Para 2 is the knife that made me fall in love with DLC for its amazing corrosion resistance.

It might sound weird, but smelling the folder is a good way to detect internal rust. My Police 3 looked fine from the outside, but the inside was coated in rust. Liners on both sides, pivot, lock bar, etc. Found out by the smell. It was so strong I could tell from arms length away.

If nothing else you can always open it up and check. I try to avoid doing that any more than I need because it can be easy to strip screws.

I’ve heard from many sources; DLC coating a blade does not help resist corrosion.

Are you sure the 800 miles of sweat isn’t the reason for that smell? I feel like it might be. I haven’t ever heard of rust having a strong smell.

[Sjucaveman]

Rust does have a telltale smell from my experience. I have had a s30v dlc para 3 rust though so it's not a guarantee. I had cut greasy salty food and didn't wash it before putting it away so it's my bad though.

[vivi]

It won't. I am incredibly tough on the corrosion resistance of things and I EDC'done for years. Carried it on an 800 mile bike tour too. Rusted the stop pin, lock and liner real bad, but the blade was pristine. The DLC Para 2 is the knife that made me fall in love with DLC for its amazing corrosion resistance.

It might sound weird, but smelling the folder is a good way to detect internal rust. My Police 3 looked fine from the outside, but the inside was coated in rust. Liners on both sides, pivot, lock bar, etc. Found out by the smell. It was so strong I could tell from arms length away.

If nothing else you can always open it up and check. I try to avoid doing that any more than I need because it can be easy to strip screws.

I’ve heard from many sources; DLC coating a blade does not help resist corrosion.

Are you sure the 800 miles of sweat isn’t the reason for that smell? I feel like it might be. I haven’t ever heard of rust having a strong smell.

Rust does have a strong smell, especially if its damp.

I can't speak for other types of coatings, or even DLC from other companies, but I can tell you that I have rusted every single stainless steel blade I've carried in my pocket besides H1 knives and DLC coated Spydercos. My DLC Manix XL, Military and Para 2 have been subjected to things that would have severely rusted even something as corrosion resistant as S30V.

I've stripped multiple fixed blades with coatings, like Izulas and Scrapyards. None of them had corrosion underneath, even knives with coatings partially worn off from splitting wood.

I've never seen a good source for DLC having a negative effect on corrosion resistance, and from my personal experience it's an absolute game changer.

[Rutger]

There is so much bad information about knife blade coatings out there. And i rarely see people provide any evidence or talk from their own experience. People are just repeating each other like monkeys. Not all blade coatings are created equal and maybe people had bad experience with fake or bad DLC from other companies. But Spyderco uses the best coatings. The DLC is bonded to the steel at molecular level, unlike many other coatings.

Michael Janich from Spyderco has posted about DLC coatings several times:
//forum.spyderco.com/viewto ... 94#p895794
//forum.spyderco.com/viewto ... 18#p878418
//forum.spyderco.com/viewto ... 48#p589348

Here is some scientific article about PACVD aka DLC coatings:
"Amorphous SiOx films provide excellent corrosion protection of steel, which is explained, on the one hand, by a tiny porosity rate, and on the other hand, by intrinsic insulating properties of the coating. This barrier effect avoids any galvanic coupling deleterious to the uncoated metallic surface, and is correlated with the SiO2-like character of the film."

[soundshaman]

I've never seen a DLC knife to rust under the coating, but one that I did see was a coated PPT sprint with rust spots. That was a different coating tho.

[Surfingringo]

I've never carried any coated DLC blades on the kayak so I don't have any first hand data. About 5 or 6 years ago though, I sold a coated pm2 to a friend who is a boat captain in the marina here. He is out on fishing charters every day and the knife sees a LOT of saltwater. About a year after he bought it he asked me if I would sharpen it. I noticed a few light rust spots blooming on the coating itself, same as they would be on an uncoated blade. I assumed at the time that the underlying steel was rusting but now I really wish I had paid more attention. It could be the steel rusting under the coating or it could be the hardware showing some rust and bleeding onto the blade as can happen in HIGHLY corrosive environments. I will make a point of asking him if he still has the knife so I can make a proper inspection. I am interested now.

[The Deacon]

From what I understand, if you totally coated a blade with DLC, leaving no bare steel at all, it would be impervious to rust. In reality there are going to be areas where the coating gets removed. The edge would be an obvious example since the coating must be removed to sharpen it, but the coating on the pivot and lock contact surfaces of a folder will eventually wear off as well and, while DLC is very scratch resistant, no coating is totally immune to damage. So, rust can form on any exposed steel and, if ignored or not seen, creep under the coating.

As for the smell of rust, I've found it to be similar to the smell of fresh blood.

[Rutger]

Exposed parts that did not get coated or are worn down/damaged will rust, no question about it. But moisture, salt or acids will not go under the coating and spread the rust like with paint or other coatings.
It will take a lot of abuse to wear down a good DLC coating. These coatings are developed for low friction and high wear resistance. This even in low or not lubricated environments. They use these coating in all kind of engine parts which take way more load than we will ever put on our knife pivots.

[Sumdumguy]

I've never carried any coated DLC blades on the kayak so I don't have any first hand data. About 5 or 6 years ago though, I sold a coated pm2 to a friend who is a boat captain in the marina here. He is out on fishing charters every day and the knife sees a LOT of saltwater. About a year after he bought it he asked me if I would sharpen it. I noticed a few light rust spots blooming on the coating itself, same as they would be on an uncoated blade. I assumed at the time that the underlying steel was rusting but now I really wish I had paid more attention. It could be the steel rusting under the coating or it could be the hardware showing some rust and bleeding onto the blade as can happen in HIGHLY corrosive environments. I will make a point of asking him if he still has the knife so I can make a proper inspection. I am interested now.

Please do let me know what you find out!

[Evil D]

There is so much bad information about knife blade coatings out there. *And i rarely see people provide any evidence or talk from their own experience. People are just repeating each other like monkeys. Not all blade coatings are created equal and maybe people had bad experience with fake or bad DLC from other companies. But Spyderco uses the best coatings. The DLC is bonded to the steel at molecular level, unlike many other coatings.

Michael Janich from Spyderco has posted about DLC coatings several times:
//forum.spyderco.com/viewto ... 94#p895794
//forum.spyderco.com/viewto ... 18#p878418
//forum.spyderco.com/viewto ... 48#p589348

Here is some scientific article about PACVD aka DLC coatings:
"Amorphous SiOx films provide excellent corrosion protection of steel, which is explained, on the one hand, by a tiny porosity rate, and on the other hand, by intrinsic insulating properties of the coating. This barrier effect avoids any galvanic coupling deleterious to the uncoated metallic surface, and is correlated with the SiO2-like character of the film."

*And then you proceed to repeat others like a monkey :p

[Sjucaveman]

After church I'll try and take pictures that show the pits from the rust on my para 3.

[vivi]

I've never seen a DLC knife to rust under the coating, but one that I did see was a coated PPT sprint with rust spots. That was a different coating tho.

I've rusted my S30V black Szabo folder, I believe it is a TiNi coating. DLC is a different beast, not all coatings are equal.

[abbazaba]

The rust still looks like rust, but it is fairly easy to remove in my experience.

My M4 DLC PM2 was my EDC outside of the office since it dropped until the REX45 dropped (which took it's role so far). It was my yard work/project/camping/hiking beater. I treat my knives like knives, but I didn't go out of my way to baby it.

Here is what it looked like this morning:




Fortunately, it is easy to rub most of the rust off with 5mins or less of elbow grease.




This has been my experience with Spyderco's DLC on the S30v model as well, FWIW. Hope this helps.

[Jazz]

I’ve heard from many sources; DLC coating a blade does not help resist corrosion.

Are you sure the 800 miles of sweat isn’t the reason for that smell? I feel like it might be. I haven’t ever heard of rust having a strong smell.

If anyone knows about rust, it’s Vivi.

[vivi]

With the pattern that rust took on M4, I am inclined to think there are particles of something on the surface on the blade, rather than the blade itself corroding.

M4 rusts much differently than that in an uncoated blade. Carbon steels in general develop large, blotchy patinas, while stainless steels develop little orange spots like that. That does not look like a carbon steel blade rusting, which immediately caught my eye. That looks more like how S30V would rust.

Of course this is just a guess. Can think you of anything that may have been a contaminate? Steelparticles from sharpening?

I had that happen with H1 once or twice, and before I came here blowing the lid off the rust proof claims I did some experimentation. Clean blade, no rust. Sharpen the knife on a not 100% pristine sharpening stone then soak in salt water, the edge bevel would develop tiny rust spots.

[anycal]

This has been my experience with Spyderco's DLC on the S30v model as well, FWIW. Hope this helps.

Same here. Both M4 and S30V.

[abbazaba]

It's possible, but I do wash and clean my blades really well after reprofiling, and this one got the Flitz treatment to remove the marks that build up in the DLC.

I agree that this could definitely be bits of something else, hence why it's on top of the DLC and comes off so easy. However I don't usually see this on my non-DLC blades.

[Rutger]

Looks like contamination to me. Should be easy to test like Vivi did with his H1. Clean and try to force it to rust.