440C and rust - is this typical?

Starfish

Starfish

Joined
Jun 14, 2001
Messages
1,256
Hi all,

A friend of mine showed me his Benchmade 550 Griptilian today, and pointed out how the edge was developing rust as well as the pockets in the thumb ridges. There was some rust in the area where the knife meets the stop pin as well.

I know that he uses the knife when he goes out saltwater fishing, so I asked him about his maintenance of the knife. He claims that he thoroughly rinses this knife with fresh water after every trip.

I called Benchmade's warranty dept. to relate these details and to get their opinion on whether the rusting was typical for these conditions, and was told "yes".

I have to admit that I thought 440C would hold up better than this, mainly due to the oft-touted corrosion-resistance properties of 440C. I'd be interested to hear the opinions of other members who have used 440C in similar conditions, as would my friend - this is his favorite knife and it bothers him to think that he might have to use his trusty Buck 110 (which has not developed any rust from similar work) rather than his Griptilian! :)

Thanks,

Matthew
 
Stainless is not stain free. I've seen LEOs with hand sweat so bad that their Model SW 66's rusted on the backstrap. One writer to a gun magazine related how a similar stainless gun was sent out for electroless nickel plating. Wow, that's acidic sweat.
 
The conditions you mentioned - saltwater on the blade being replaced by fresh water - could eventually rust anything. The Buck 110 might dry before it reaches that rusting time, but it can rust, too.

Benchmade sells a new dive knife with a steel touted to be really rust resistant, but it's a fixed blade and may not apply to your friend's situation.

Would your friend consider an S30V bladed knife like the Spyderco Native FRN?
 
Originally posted by Ichabod Poser
Stainless is not stain free.
Click to expand...

Yep - but different stainless steels have varying levels of corrosion resistance. 440C is not ATS-34, after all.

@Thombrogan - my friend is sold on Axis lock knives, as he appreciates the one-hand closing aspect that does not require his fingers to be in the path of the blade.

However, if you are suggesting that S30V could stand up to a saltwater environment with nothing more than a freshwater rinse for maintenance, I could probably convince him to buy a 921 :)

Matthew
 
Starfish,

All steels will rust under those conditions. The Buck 110 has a slightly lower carbon content so it will rust slower, but that is the tradeoff. The salt water is very corrosive. You can fix the problem by rinsing the blade in fresh water and then coating it with a lite coat of oil. About the only thing that would be completely unaffected would be Titanium (like the Mission MPS/MPK series), Talonite, and Ceramic.

n2s
 
Matthew, 440C is the best of all SS when it comes to rust resistance that i know of, well more rust resistance then the tougher AST34 for sure!

I would call the maker again and ask for a RA# so i could return it for a replacement, i wouldn't take no for a answer myself since i know without doubt it is not normal for 440C to rust at all, like i said 440C is the best of all SS when it comes to rust resistance!

James
 
440C is definitely not the best steel for rust resistance. Either 440a or 440b would are more rust resistant(but also a less desirable steel, due to lower carbon content). And the 420 series are even more rust resistant. Another thing, besides just composition, is the treatment. I don't know knife you're talking about personally, but a bead blasted finish will rust faster than a mirror polished blade, as there are microvoids that trap the water. But it is not unreasonable at all for 440c to rust in such a situation. As already said, only thing that wouldn't rust in this situation would be a nonferrous blade such as a ceramic, titanium or stellite blade, which have their own tradeoffs.
 
Originally posted by Starfish
My friend is sold on Axis lock knives, as he appreciates the one-hand closing aspect that does not require his fingers to be in the path of the blade.

However, if you are suggesting that S30V could stand up to a saltwater environment with nothing more than a freshwater rinse for maintenance, I could probably convince him to buy a 921 :)
Click to expand...

I haven't tried doing that with mine yet, so I can't endorse such a move. Also, with the 440C slipjoint, there'll be some corrosion.

Have you considered selling him on the framelock goodness of the CUDA Talonite EDC? Our friends at New Graham Pharmacy list them for $137.50. Or, if the axis lock has to stay, maybe a teflon-coated 921 in green or red? I think that Talonite will work better for him than 440C or S30V and I'm not willing to dampening my knives to see how well they'll rust yet, so I'd push for either the Talonite EDC or a return to his Buck 110.
 
If he needs absolutely rust free performance and zero maintenance he should go with Talonite, Stellite or Titanium.

I have seen 440C rust and it's usually when zero maintenance has been performed and primarily in rougher finished areas (like you described). High polish adds a lot to rust resistance and the area's that your friends knife is rusting in are not usually polished.

Also, I would reccomend he use more than fresh water to clean with. Water is hardly a rust inhibitor. Even a shot of WD-40 would probably prevent the rust he's getting.
 
thombrogan, we posted at the same time - great minds think alike ;)

I wanted to add that he could also consider taking a polishing wheel to the area's he's getting rust and it will probably help.

But nothing short of a rust free alloy will totally negate an absolute lack of maintenance.
 
Originally posted by cpirtle
thombrogan, we posted at the same time - great minds think alike
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Wow!

Not only am I being accused of having a mind, but a great one! Thanks, CPirtle! My guess is that it takes less patience to shell out $140+ than it does to disassemble an axis lock, polish every water-accessible part of the knife, and then reassemble it. I got one axis lock back together once and then bugged my wife to put the others back together for me because I lacked the necessary finesse. I'd spend the money because I think that I'd end up wasting more irreplaceable hours of my life reassembling an axis lock than I would recouping the monetary loss (which is also a representation of time spent laboring on this Heaven Below, but easier to obtain).
 
Just because a SS has less carbon in it, doesn' make it rust "less". SOG's 440a will stain quite easily due to the grain structure. A little known fact that I had discovered two years ago.
 
If he's a knife nut and he has to use a knife in that kind of environment, invest in a talonite blade.
I've a AUS 6 folder with bead blasting finish that rusted during heavy (and I mean heavy) rain for a few days in a row. It just was way too humid for it.
If even AUS6 (akin to 440A) rusted, think about what saltwater does to 440C.
 
Thanks all, for the well-informed replies. I've not had a problem with rust at all in the relatively short time that I've been a knut, so I don't have much experience to draw from regarding rust prevention. I usually just put a light coat of Rem oil on my blades once in a while and that seems to work for me.

My friend is not a professional fisherman or anything, and I'm certain that he won't pay for Talonite or similar - it took him long enough just to pony up for the Griptilian :rolleyes:

Sounds like I need to explain to him the tradeoffs involved in selecting a knife for marine applications, as well as introduce him to the world of Tuf-Glide and other rust prevention techniques :p

Thanks again,

Matthew
 
Can't tell how long your friend has been using the knife, but it doesn't sound like a lot of rust. A little on the stop pin, on the edge and in thumb ridge recesses, sounds like a minor problem fixed in less than 5 mins. Maybe a little more vigogous rinsing will help or he may need to wipe the blade edge after use. One thing that helps is to sharpen with an oil stone. The oil helps rust proof while sharpening. Honing oil makes a good cheap anti-rust agent.
 
One of the major causes of rusting of stainless steel is contamination with carbon steel. When stainless steel is ground, polished bead blasted etc on the same equipment that has been used on carbon steel small particles of carbon steel may become imbedded on the surface of the stainless and those particles rust and continue to rust into the stainless. There is a treatment for minimizing the problem , the stainless steel should be ' Passivated ' This treatment cleans the surface of impurities and builds up a thicker layer of protective oxide. It is a standard treatment for stainless steel.
 
another thing i picked up from this thread is that people associate carbon content with rust resistance
afaik it's the free chromium (ie % Cr - % C) that determines how stainless the steel is
i remember reading at least 12% of free chromium is needed to call the steel stainless
is that right?
 
I think that 12+% total chromium is needed to call the steel stainless, maybe 15+%. I don't think many people delve into whether the chromium content is bound into carbides or nitrides.
 
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