INFI Corrosion resistance

Cobalt

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This always seems to be a topic of contention. Most of us that use INFI know it has very good resistance considering that it is not a stainless steel. But in looking around I found this and it is very telling. I find it interesting how INFI compared well to VG10. I myself have had similar experiences with ATS34 vs INFI. Good reading below. Hope you enjoy.

I examined the corrosion resistance of M-INFI several times and each time was impressed with the results. The first time I just left the blade covered in a 1/2 litre of water for 3 and a half hours. This however failed to induce visible rusting or make any impact on the slicing ability. Making the environment a little harsher I put it back into the water and poured a tsp of salt across the
blade. Five and a half hours later the blade was examined and a three very small rust spots were found, being about 1 to 2 mm across. The edge did not feel significantly different. Ten hours later the blade was examined and no additional rusting was evident. The slicing ability still had not significantly degraded. All rust was then removed easily with a Scotchbrite pad and the edge restored to the x-coarse finish.

Making the environment a little harsher and including the TOPS Steel Eagle for reference
(1095), I put both blades in a steel pan. Each knife was covered with water (3/4 litre) and 2 tsp of salt was poured along each blades. After five hours the TOPS blade was covered in rust along any non-coated area (as expected) and the slicing ability of the blade was cut almost in half. The edge on the Basic was not effected and the blade showed little effect from the soaking except for
a few light rust spots along one side of the bevel (the side facing the metal pan). The rust on the Basic was removed when the blade was dried, the only resulting effect was a few water spots visible along the bevel.
The TOPS blade still had rust remaining after drying (much was removed though) as some parts of the blade are engraved and ground out (blood groove and such) and escape contact while drying. Interesting enough, the TOPS blade formed a lot of black rust as well, this was not present at all on the Basic. After drying the blades were again exposed to a corrosive environment.

This time determined to effect the Basic I poured a mixture of salt and water (2 tbsp per 8 oz) over each blade, put both in the metal pan and then added an additional 8 oz of the salt water. This left the blade exposed to the air as well as the water and I hoped the movement of the air would induce
rusting faster. After 4 hours I checked on both blades and this seemed to be evident. The TOPS blade was again completely covered, with corrosion, mainly black rust though as I never removed much of it from the last soaking. The Basic had some spots along the spine and the bevel. When the cutting ability was checked a significant difference was noted in both blades.

Based on that it would seem to me that you would need a fairly corrosive enviroment in order to worry about functional degredation due to rust. I have not seen any in actual use. When it thaws here I will lend both Busses to my brother as he frequently goes saltwater swimming.

-Cliff

Recently I have been doing very high stress corrosion soaks as I wanted to examine the ability of Talonite to resist rusting. I was doing about 20 hour soaks in a salt solution of 8 table spoons of table salt per litre of tap water. The Talonite didn't rust but what I found interesting was that I was seeing large scale edge damage to D2 and even VG-10 and ATS-34 blades.

Under a scope at 10X mag I was seeing small chips like about .1 mm deep. However when I tried to sharpen the blades the edges went to pot and the chips blew up to about .3 mm in depth and whole sections of the edge up to 1 mm in length cracked off. I repeated this a few times, which was a real pain as it takes a day to do the soak and a lot of time to grind all the weakened metal off the edge, and the results were very consistent.

What does this have to do with Busse Combat? When I did this a few months ago on the Basic I didn't remember seeing any edge damage after the soaks, I saw rusting but the blade sharpened easily on an 800 grit ceramic rod. However I was using a milder solution and not soaking as long so I couldn't accurately compare the results. But of course it was fairly easy to check.

I first soaked the Basic by itself and then with a VG-10 blade. As before the VG-10 blade showed functional edge damage and required a significant amount of work to restore the edge. However what surprised me was that the Basic showed less damage both times. Even though I did see rusting visible on the blade the edge did not get as damaged nor did it crack apart when I attempted to sharpen it. It took 15 strokes per side on an 800 grid ceramic rod to restore it to push shaving sharp.

This doesn't make a lot of sense to me, I would have expected the stainless steels to be less effected along the edge. However rusting is very much a random process and I will repeat the soaks a few more times before I am satisfied that I am seeing a real effect. It is interesting though. I think I will get my BM back and do it with it as well.

Jerry, yeah, we are not too distant relatives, Grandpa has me in the looks department but I am probably a little brighter.


-Cliff


[This message has been edited by Cliff Stamp (edited 02-14-2000).]
 
Interesting, thanks for pulling that Cobalt :thumbup:
I'm a little embarrassed to say, that I never thought about edge deformation/degradation from corrosion. In a long term scenario, without the ability to clean up rust spots, you could be left with essentially cancer of the blade, slowly eating away at your (arguably) most valuable tool.

Very cool. Glad INFI can hold its own in that area.
 
I always liked Cliff's stuff.

I salt water kayak and wade fish with my meaner. No sweat, ever. No rust, nothing. Compare that to the other knife I had this day. The Tenacious (8Cr13MoV) after several hours exposure...

IMG_0309.jpg


IMG_0314.jpg


.
 
Cobalt, thanks for the blast from the past...

Hey, was it M-INFI exclusively that Stamp was testing corrosion with?

Wonder if there's a noticeable difference in the corrosion resistance of M-INFI vs. full-blooded INFI?
 
Cobalt, thanks for the blast from the past...

Hey, was it M-INFI exclusively that Stamp was testing corrosion with?

Wonder if there's a noticeable difference in the corrosion resistance of M-INFI vs. full-blooded INFI?

No, he tested both. The first quote was M-INFI, the second was INFI
 
Another interesting quote

07-23-2000, 12:24 AM #195 Doc Ron Doc Ron is offline
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About corrosion resistence. I've had INFI in the SA jungle twice on 6 week trips. We put it to the test. It does corrode and it does rust. A tufcloth or other coating will mitigate the rust. The rusting I saw was minor and would rub off with a piece of cloth or at worst, a green pot scrubber. Some of the "stainless blades" I saw looked worse. If you cut meat with INFI the natural animal oils should do a tolerable job of keeping the blade rust free. WHen I came back last time I left the blade in the wet sheath when I put it away. A few weeks later I was cleaning my gear and remembered the blade. It had a fine layer of rust in odd patterns decorating the blade. I cleaned it with a green pot scrubber. It was mildly discolored. My INFI BM does NOT have the black ceramic coating.

Talonite did not rust, discolor or change in any noticable way. I never used protection for the blade.

Ron
 
and more

I have used both M-INFI and INFI in wet and dirty conditions, including around and in saltwater. I have also done long soaks (24 hour) on both blades in salt water solutions (1tbsp per cup, or similar, which is really salty). The M-INFI blade was used for over a year without oil of any kind because the person who I lent it to thought it was stainless.

I have noticed that INFI will resist rust stronger than most plain carbon or low alloy steels (L6). For example, a few weeks ago I spent about 6 hours in the rain with a Battle Mistress, PAB from Strider, a Hatchet from Gransfors Bruks and a few saws. What I found was that while in use chopping (alternating every other piece of wood, about 10 minutes in between use per rotation) neither blade rusted. However as soon as I switched to the saws the Gransfors Bruks hatchet rusted readily.

This really isn't a surprise as the hatchet it is most likely a bandsaw steel (L6-like) or something very close to it and they will rust readily if exposed to water. If you really want to see just how easily such steels can rust thenexpose them to fruit juices, the acids will put a patina on them *very* quickly*, just a few minutes. I cut up an apple with one awhile back and before I the tv program I was watching went to commercial all the contact area had turned.

In regards to comparing INFI/M-INFI to stainless steels, most stainless knife alloys would resist the initial formation of rust stronger than INFI/M-INFI. However based on the long soaks I have done, they tend to take much more extensive damage when they do rust. Mainly they suffer extensive pitting which cannot be removed without a surface lapping (or a chemical treatment which will leave pockets in the finish).

For example using identical salt water solutions on VG-10, ATS-34, D2 and INFI. The INFI blade after a mild cleaning (a few passes with a worn scotchbrite pad) was left with a smattering of small black oxide specs (<0.2 mm in diamater). The other blades had sufrace corrosion that was extensive (>cm in size) and deep enough that even a mild sanding did not remove it (the D2 blade was more extensively damaged than the stainless blades). Most of the specs on the INFI blade (Battle Mistress) came off with use. The only ones that remain are not in frequent contact areas.


I should qualify though, that blades will only rust if left *unused* in corrosive enviroments. The hatchet I mentioned in the above for example was cleaned of all the surface rust from abrasion when I switched back to chopping. As well the blade that rusted after cutting the apple was left unused for about 10 minutes after it sectioned the apple.

One other thing, INFI is not as corrosion resistant as the more rust resistant stainless alloys like 440A. I have a 440A fillet blade in a salt water solution now for a week and it shows only a slight surface rusting in a few areas that would wipe off with a cloth. The piece of BG-42 I have in with it is completely covered in deep black and orange oxide. Most high end cutlery stainless blades do not leave a significant amount of free Cr in the steel so their corrosion resistance is low. Doesn't do the steel any good corrosion wise if the Cr isn't free, regardless of the percentage in the mix.

-Cliff


[This message has been edited by Cliff Stamp (edited 05-22-2001).]
 
The "long soak" data is very interesting. Apparently, I needn't be quite so obsessive with my use knives.
 
This means the Busse Diving Knife needs to happen.

It was made.... It's called a stealth hawk, the perfect dive knife/ Bomb squad knife.

Imagine infi but plastic..More technically MP45. .25" thick and can be hammered through a 4"x4" with no damage....
 
WHAAAAAAAAAAAAAAAAAAAT

Stealth_Hawk_box_50.jpg


Also I forgot about this one:

IMG_1871.jpg


So I guess what I meant to say is "This means another Busse Diving Knife needs to happen"
 
I have had much more rust show up on S30V than Infi. Rust spots on S30V and never any on infi.
 
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