Dive Knife Material vs. Corrosion: Titanium, H1, LC200N

[drrich2]

A common issue in diving is what cutting tool to get. Some prefer line cutters like the Trilobyte or Dive Gear Expresses' EZ-Cutter, some EMT shears, and some knives. Then the discussion may get into a debate over some options:

1.) Cheap disposable route - such as break the point off a cheap steak knife.
2.) Moderate cost options that rust up if you don't way on top of care - the typical 'stainless' (what a laugh) steel dive knife. Unlike the D-rings on you BCD, that blade can and will rust up readily.
3.) Titanium - light weight, roughly double the cost of a standard stainless steel dive knife, but 'buy once, cry once.' Some titanium dive knives come with a sheath to mount on your harness or thigh. Roughly double the price of a stainless steel dive knife when I looked.

Those who read enough of these threads may be aware of another option, H1 steel, usually in the context of some (not all) knives produced under the brand Spyderco. I have one, and it's handled markedly neglect on multiple live-aboard and at least one Bonaire trip, amongst others. I'm told a bit of rust at the letter carved into the blade, perhaps from residue from the non-H1 drill bit, might be a factor...and that happened. Over the years I've started to see a small amount of rust, but nothing to compromise the knife's function. Someone reported getting one to corrode by extended direct contact with a chlorine tablet (likely for a swimming pool) - so I don't do that.

Just what the major selling points of H1 vs. titanium steel are I'm not certain. H1 has a lower amount of carbon, and substantial nitrogen, in the metal.

Today, messing around online for other reasons, I stumbled upon another highly corrosion-resistant steel used in knife blades, LC200N (a.k.a. Cronidur 30). Spyderco sells knives using this steel. I don't recall seeing it mentioned on ScubaBoard, so maybe it's worth a mention. Here are some links with more:

KnifeSteelNerds.com (proof there really is somewhere for everyone on the Internet) - LC200N/Cronidur 30 - History and Properties. Talks about the difficulty of getting nitrogen to stay in steel rather than bubble out. "It was developed as a bearing steel using a specialized production process (pressurized electroslag remelting), to increase the nitrogen content of the steel through high pressure. The partial replacement of carbon with nitrogen gives the steel improved corrosion resistance and toughness when compared with the carbon version, X50Cr15Mo. LC200N has a max hardness of about 60 Rc, which is probably its biggest limitation. Its edge retention and wear resistance is similar to other low carbide steels like AEB-L and 14C28N. The steel has excellent corrosion resistance and toughness as well. This gives LC200N a very good combination of properties." Note: CherokeeObserver (see below) didn't indicate LC200N to be exactly the same as Cronidur 30.

Spyderco.'s Forum - I did a search on LC200N vs H1. I get lost in some of the abbreviations and minutiae the knife aficionados use.

CherokeeObserver.org - What Is LC200N Steel? LC200N/Z-Finit Knife Steel Review. It first appeared in 2013. They note is shares an 'almost similar' composition with Krupp's Cronidue 30 (which has been around a lot longer). "LC200N is a high nitrogen alloyed tool steel with extremely high corrosion resistance performance. The steel is produced using ESR technology (Pressurized Electric Slag Remelting) for increased cleanliness and a refined micro-structure—giving the steel high machinability and polishability. Knives with LC200N are loved for their superior corrosion resistance and high toughness at a high hardness of over 60 HRC."

Some of their other comments:

"This is the typical hardness level you get for knives from most high-end manufacturers. You can trust an LC200N knife blade within this hardness range to offer you great wear resistance and excellent sharpness for longer than the cheaper knives."
"This steel offers decent wear resistance, but not something comparable to steels like D2 which has tremendous wear resistance. Nevertheless, this steel still offers you a good amount of wear resistance—good enough to resists everyday tear and wear and prevents the edge from deforming as you go about cutting various materials."
"The high LC200N edge stability lets you use your lc200n knife to do a lot of daily cutting for months without losing its sharp cutting edge."
"LCN200N is reasonably tough and offers good resistance to chipping, cracking, or breaking under stress or impact. Its toughness is pretty similar to what you get with H1 steel."
"If you want to feel what it’s like to have a 100% rust-free knife, get yourself an LC200N steel knife. This steel is made of exceptional corrosion resistance and can go through tons of sweat, water, saltwater without catching stains. LC200N is ultra-stainless steel. LC200N steel is rustproof!"
"LC200N sharpening is an easy task. This steel features a fine grain structure that enables you to effortlessly sharpen it to a hair-popping sharpness level."

This bit is particularly interesting:

"LC200N Steel Vs H1
Both H1 and Lc200N are nitrogen steels and many knife steel experts believe that Lc200 is the upgraded version of H1. H1 is softer steel compared to LC200N and this gives LC200N better edge retention. H1 has poor edge stability and gets dull pretty quickly when put to hard use.

H1 outshines Lc200N with higher toughness and holds up well to tough use. However, both steels find a common ground in that they’re extremely corrosion-resistant (both are regarded as rustproof steels) and are super easy to sharpen. H1 performs better in a serrated knife while LC200N gives better performance in the plain edge."

Spyderco Forum - LC200N and corrosion resistance...new observations. He tried to make it fail in various ways, mainly by exposure to extreme levels of corrosive environment. He found H1 to be a fully rust-proof steel; he'd never been able to corrode it in any way (but saw some corrosive bleeding from some hardware or residue corroding on the blade etching, but not on the H1 steel itself). He tested a LC200N and found it 100% corrosion proof until eventually detecting a tiny spot of rust, easily wiped off, but with very tiny pitting on the steel. But he's had multiple LC200N knives with saltwater exposure and no corrosion. He speculates as to what may've happened. He prefers LC200N to H1 for plain edge knives by a wide margin, and reported getting better performance out of the edge.

Stripersonline.com - Spyderco users, H1 serrated vs LC200N serrated. The original poster states:
"Ok knife nerds, does anyone have experience with spyderco’s serrated knives in both LC200N and H1?

It’s well documented that H1 has better edge retention in SE than PE and that LC200N has better edge retention in PE than H1 in PE.

How similar are the steels in edge retention and toughness when they’re both serrated?

But in Post #6, a custom knife maker who notes he's an engineer wrote:

"H1 and LC200N are both nitrogen based stainless steels with low carbide volume and wear resistance. They'll be easy to sharpen and take a keen edge. The difference between the steels themselves might be 5% in a laboratory. The difference between them in the real world will be imperceptible. Get the knife that has the better edge geometry, handle design, and if price is a factor, that too."

But in Post #9, he said "LC200N is a low carbide non-age hardening nitrogen stainless steel. High toughness (for a stainless) and low wear resistance. Should be much easier to sharpen than H1." Another poster in Post #14 noted "- LC200N has a different sharpening response than H1. More crisp feeling and less “gummy” on the stones. It sharpens quite easily and takes a very fine edge with little effort." Another in Post #7, of H1, wrote "That said, I find them VERY difficult to sharpen. The h-1 steel is really hard to upkeep. Ill admit it may just be my sharpening skills but I don’t have as hard of a time with my other Spydercos."

BladeForums.com - LC200N and Salt Water. He dunked it in the ocean, folded, pocketed, 24 hours later, very minimal rust that came off pretty easily via a cotton swab dipped in acetone.

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[drrich2]

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So that's a lot about LC200N vs. H1. What about H1 vs. Titanium?

Spyderco Forum - Titanium vs H1 steel ?? Leif wrote "H1 will have much better wear resistance. Ti is much softer than steel, and usually when knives are made out of it the edge is carbidized to make it harder. But this also means you can't sharpen it unless you have a way of carbidizing it yourself. Un-carbidized titanium can't hold an edge very well at all. I would much prefer H1."
Cliff Stamp wrote "You can sharpen carbidized titanium with regular benchstones, as it is done usually on one side so you just sharpen the other one. The thing you need to be careful of is that you can not use standard techniques like burr-sharpening because if you do you will defeat the carbidizing purpose completely.

There are many forms of Titanium used in knives, in general :

-they tend to be fairly soft, ~45 HRC and thus can dent/roll easier
-they are very impact tough
-they are fairly weak and easy to bend (and thus usually have thick cross sections)

In general unless you need some of the special properties of Titanium (it is very light for example) it is hard to argue why you would want it in a knife."

Darkangel55555 wrote "My titanium bladed knives have bugger-all edge retention. Can't get them as sharp as steel, for some reason."

Opusxpn wrote "Titanium is not good for the edge retention, I have only seen one titanium dive knife blunt tip chisel grind. I also think H1 is superior."

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Now to the point of this write-up/discussion. I'm not out to argue whether people ought to get a line cutter (I have one) or EMT shears instead of a knife, or whether to use cheap steak knives disposables. I do advocate getting a rust-proof knife over a half-the-price stainless steel dive knife that's rust and get replaced.

But for those of you who, like me, want a 'buy once, cry once' rust-proof dive knife:

Why is titanium the de facto standard in rust proof dive knives sold as such (e.g.: by scuba equipment vendors and brands)? Titanium, H1 and LC200N are all expensive.

Other than not getting a BCD harness-friendly shealth included with some, is there any reason you'd prefer a titanium dive knife over a H1 or LC200N dive knife?

Some examples:
Amazon: Spyderco Salt 2 Folding Knife with LC200N Steel Black. $116.20.

Amazon: Spyderco Salt 2 Lightweight Folding Knife with 3" H-1 Ultra-Corrosion Resistant Steel Blade and Yellow FRN... $96.25.

LeisurePro: I see a wide range of prices. The Blue Reef Scuba Titanium Folding Knife for $24.95 ($19.95 Cyber Week special) with about 4 1/2 stars from 80 reviews looks promising, but I see some around $140. A key difference is scuba diving knives don't tend to be foldable. Not all Spyderco knives are, either, but mine is. Going for a recognizable brand name that's not associated with high prices, that looks a bit similar to the others but not foldable, see the XS Scuba Neuro Knife Titanium for $89.85 or Aqua Lung Wenoka Big Squeeze Lock Titanium Knife, Tanto Tip for $99.95 (both - 4.5 inch blades) or Aqua Lung Big Squeeze Lock Knife (4.25 inch blade) - $67.00.

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[Akimbo]

Impressive work, thank you.

LC200N is ultra-stainless steel. LC200N steel is rustproof!"

Technically, stainless steel is never "rustproof". Highly rust resistant would be more accurate. Titanium alloys are rust-proof because there is no iron to oxidize (iron-oxide is rust). However, some Titanium alloys do oxidize in seawater.

Stainless steel is mostly iron and ~11%+ chromium is added. The chromium forms an micro-thin "passive film" layer of chromium-oxide on the surface. That layer protects the underlying iron from being exposed to oxygen so rust cannot form. The chromium-oxide layer is normally "self-healing", which means that chromium-oxide will quickly form in areas where the original layer is damaged.

There are exceptions, like when a scratch leaves behind "contaminants" that inhibit the formation of the protective chromium-oxide layer — like iron particles for example. It can be as little as minor surface staining to serious pitting.

You often hear the term passivating relating to stainless steel. It refers to a chemical treatment that accelerates the creation of the chromium-oxide layer. It is often done to finished stainless steel parts that were machined, welded, and/or formed, which damages and contaminates the stainless surface.

One of the processes that can contaminate the chromium-oxide layer is sharpening when done improperly. Common culprits include:

• Sharpening with steel tools, like files.
• Sharpening on surfaces contaminated with micro-fine iron particles. Sharpening with grinding wheels, stones, and diamond plates that were also used on steel alloys for example.
• Sharpening with abrasive media (sand paper, belts, disks, etc.) that was also used on steel alloys. Quality stainless steel fabricators strictly segregate tools used on stainless and steel alloys.
• Sharpening against steel or cast-iron plates, usually with water or oil and micro-abrasive mixtures.
• Using "honing steels" that are steel instead of stainless steel.

Unfortunately, this best "marine grade" stainless steels can't hold a good cutting edge because they are too ductile. The microscopic serration on the sharpened edge fold over too easily.

 

[San Diego Climber]

Spyderco Saver Salt on my harness (Saver Salt® FRN Yellow - Spyderco, Inc.) and close to 200 dives on it, looks brand new. The H1 steel is awesome.

 

[doctormike]

I guess my question would be that unless you are spearing and need to kill fish, why would you not just use trauma shears?

For the actual intended purpose of cutting yourself free from intanglement, shears are vastly more efficient and safer than any knife. Titanium shears are $8.00, I have had my current set on my rig for a few years. I guess they are a bit tarnished, but if they ever stopped working I would just replace them. I have never seen the joint break, and they will cut through just about anything without the risk of cutting yourself. The one time I tried to use a dive knife to do something scuba related in Cozumel, it ended up with me searching for a tetanus booster at a local pharmacy...

Am I missing something? Why it has to be a knife at depth? This seems to be a LOT of work, cost and worry to keep the knife in good shape - something that I never consider with trauma shears. I do carry a trilobite as a backup (another safe and convenient option, but not as multi-purpose as shears).

Sorry, I know that wasn't really what the point of this thread was, but I'm always willing to learn!

 

[Akimbo]

I guess my question would be that unless you are spearing and need to kill fish, why would you not just use trauma shears?

It all depends on the job. A knife (or knives) is a better option for wrecks covered with layers of fishing nets — though good quality hedge clippers work even better. A knife is a better choice for clearing fouled propellers — though a hacksaw with a fine-tooth blade is even better. Same for recovering lost anchors where line is used for most of the scope instead of chain.

Trilobite-style cutters are a decent option for divers exclusively concerned with monofilament fishing line, which is easily the most insidious risk to most recreational divers.

A pre-1980s BFK is great for rock scallops and smashing sea urchins on the West Coast, bur really lousy for cutting anything because the vast majority were made with soft marine-grade stainless.

A downside of sheers is they less effective in ambidextrous situations. They also don't lend themselves as well to tethering. Loosing an inexpensive cutting tool is not so bad as loosing an expensive one, unless you need the darned thing:

 

[doctormike]

I defer to your experience, but I think that a shears works better in many of those situations. And certainly no reason why you can't put a tether on shears either. I agree that the trilobite is a very limited backup option.

 

[drrich2]

I guess my question would be that unless you are spearing and need to kill fish, why would you not just use trauma shears?

I've already read of people using a dive knife as a pry bar; don't recall why. I think many people are accustomed to using knives for various things, and that familiarity colors their choice of dive gear.

I, too, have a Trilobyte - I like the very low profile, 'set it and forget it' presence on my harness.

Titanium shears are $8.00, I have had my current set on my rig for a few years. I guess they are a bit tarnished, but if they ever stopped working I would just replace them. I have never seen the joint break, and they will cut through just about anything without the risk of cutting yourself.

Thanks for reporting the good experience. Years ago I bought a Black Friday special 'titanium coated' cheap dive knife, and it rusted up quite readily. Your link says heavy-duty stainless steel blades with titanium nitride coating to resist corrosion. Cheap enough to replace if they ever get dull. Also glad you mentioned the joint held up.

Why it has to be a knife at depth? This seems to be a LOT of work, cost and worry to keep the knife in good shape - something that I never consider with trauma shears.

To me, a major selling point for H1 and LC200N knives is that they are not a lot of work and worry to keep in decent shape (I'm about function more than form; a slight orange glaze patch I can live with). A standard stainless steel dive knife, on the other hand, can be exactly what you describe - after the dive, quickly get a fresh water rinse and dry it. Too much hassle.

One question that comes up...is your cutting tool solely for diving, or do you carry it in other activities (e.g.: as a general purpose pocket knife)? I used mine this morning to pop the balloons cluttering our floor to throw away while our kid's at school.

 

[dfcliff]

I defer to your experience, but I think that a shears works better in many of those situations. And certainly no reason why you can't put a tether on shears either. I agree that the trilobite is a very limited backup option.

How do the shears do at cutting wire fishing leaders?

Thanks!

 

[Akimbo]

How do the shears do at cutting wire fishing leaders?

Thanks!

Depends on the shears and the fishing leader. One of these works on most of the commercial leaders.