Vox,


Mmmmmm.... Puzzle "NOT" solved... for me.

In some ways: Puzzle "Created". <img src="/ubbthreads/images/graemlins/confused.gif" alt="" /> <img src="/ubbthreads/images/graemlins/frown.gif" alt="" />


I have read where Jerry mentioned this and at the time, I just disregarded the comment regarding: "INFI has similar rust resistance to ATS-34 and D-2 due to the carbon to chromium ratio" as "drink" (assumed lots of Bourbon <img src="/ubbthreads/images/graemlins/wink.gif" alt="" /> <img src="/ubbthreads/images/graemlins/loopy.gif" alt="" /> ) speaking. <img src="/ubbthreads/images/graemlins/loopy.gif" alt="" /> <img src="/ubbthreads/images/graemlins/wink.gif" alt="" />

I fully believe Jerry to be an expert and very knowledgable about steel or at the very least be way more knowledgable than myself. And I am under the impression he could probably speak quite knowledgeably about steel and steel properties while drunk than most anybody else sober.

Actually, the irony is that Jerry seems to be very "tight-lipped" about talking technical info about steel when sober. And conversely, seems to be much more likely to openly discuss steel technology when drinking. <img src="/ubbthreads/images/graemlins/rolleyes.gif" alt="" /> ( <img src="/ubbthreads/images/graemlins/doh.gif" alt="" /> <img src="/ubbthreads/images/graemlins/banghead.gif" alt="" /> )

But, as much as I like to research and know "Why" things are what they are and do what they do. I tend to often have to believe what I "See" (.... even if with my own "lying" eyes <img src="/ubbthreads/images/graemlins/confused.gif" alt="" /> ).


For starters, for those who might be curious about "Decarb":

"Decarburization is an oxidizing surface condition caused whenever ferrous (carbon based) metal is heated to temperatures above the visible heat (960 degrees F) zone, and is exposed to atmosphere. This is a natural and common occurrence associated with forging and heat treating. The surface in this condition has lost carbon composition (de-carbon-ized) and scale (loose flaking surface which resembles the scales on a fish) will also become evident. Hardness in this layer is poor to none." "In fact, if a tool is put into service with any appreciable decarburization, it can show surface breakdown quickly."

A ridiculous amount of technical info about “stainless Steel Refining” decarb/decarburization, etc. can be found here: Stainless Steel Refining



.... so it seems to me that it would be best if this layer were removed. (????). However, it seems apparent that most coated blades have “some” of this layer left under the coatings. I have stripped a lot of coated blades and seem to recall always finding this "gray" layer under the coatings. Only the LE blades (and most satin blades offered by 99.9% of the knife-makers in the world remove all of this layer.

Most knife-makers grind this layer off.

I have to ask and wonder: If this is a layer known corrode at a faster rate, why is it left on the blade and not "thouroughly" cleaned off prior to being coated? <img src="/ubbthreads/images/graemlins/confused.gif" alt="" />....

.....Or (in my case - preferrably at a reasonable price like other knifemakers <img src="/ubbthreads/images/graemlins/crossfingers.gif" alt="" />) just cleaned off (made satin) and NOT coated?

Apparently, coated blades are coated as a simple and (slightly) cheaper solution. <img src="/ubbthreads/images/graemlins/barf.gif" alt="" />

I “assume” some theory is that the coating might prevent further oxidation from occurring by helping prevent exposure to oxidation. But, if there is any moisture or oxygen trapped under the coating, there will be issues. And apparently there have been a few (although apparently very rare) cases were corrosion appears to have occurred under the coatings.
I assume either too much decarb was left prior to coating - enough to continue oxidizing. Or, somehow some moisture was trapped under the coatings. (?????) <img src="/ubbthreads/images/graemlins/confused.gif" alt="" />

*** In all fairness, I have NEVER seen any significant corrosion under any of the coatings I have stripped. <img src="/ubbthreads/images/graemlins/thumbup.gif" alt="" /> <img src="/ubbthreads/images/graemlins/thumbup.gif" alt="" />


As detailed as Busse is about some things, I have to assume there is a chemical and/or heat process to quench oxidation prior to coatings. But, I don't expect Jerry to reveal his process.


There are some recent issues with corrosion under the "scales". But, that is another issue and likely due to leaving an INFI knife outside at night for about 4 hours in (assumed) humid conditions. Nevertheless, more evidence of INFI's ability to readily rust/corrode.

The LE blades are appropriately refinished (IMO) "machined" to removed the outer affected decarb layers. So, while they don't have the issues associated with decarb, they will still rust.

CE blades are apparently more in question if a decarb layer is left being exposed. (????) <img src="/ubbthreads/images/graemlins/confused.gif" alt="" />



--------------------------

But, what begs the question for me is still the comment about comparable corrosion resistance to “ATS-34 and D-2”…….


---------------------------

Aside from the "Decarb" issues, my brained was tweaked over the comparison of INFI to ATS-34 and D-2.

I have owned a pretty large amounts of ATS-34 and a few pieces of D-2 and enough pieces of INFI and worked with the INFI enough to see it rust. It doesn't rust quickly or readily at all compared to SR-101, 1095 and similar. But, it DOES rust. I have "Seen" INFI rust and there are plenty of examples of INFI rusting. Further, I have seen freshly sanded INFI with all possible layers of decarb removed – INFI still rusts.

Other reliable sources have also firmly stated reasonably fast signs of rust on freshly sanded blades and/or other indications of INFI rusting.

Again, I am confident from what I have seen that INFI is much less prone to corrosion than many other non-stainless steels, but from all counts that I have seen, INFI rusts much more readily than ATS-34 (same as 154CM with same carbon/chromium counts and "ratios") or D-2.

Another interesting part of the comment from Jerry to me was "ratio".

You don't hear the part about carbon to chromium "Ratio" mentioned much at all, but from my understanding, "Maybe" (??????? <img src="/ubbthreads/images/graemlins/confused.gif" alt="" /> ) ratio is more relevant than the more commonly referred to "percentage" of chromium.

I am not a metallurgist, but I like to research stuff. Unfortunately, there is a lot of mis-information on the internet and we have to try hard to avoid "traps" of believing what we read. At some point, if enough various sources support the same claims, I tend to allow myself to cautiously "assume" it may be so.

Generally speaking in regards to stainless steel, it is commonly accepted and often discussed that while most steels that are referred to as "stainless" can still be subject to some amounts of varying degrees of corrosion, stainless steels are "generally" considered stainless if they have about 12% - 13% chromium.


The following are a few quotes that help describe my (assumed) (possibly" better and more accurrate (????) understanding of how chromium help make steel stainless:

"The chromium in the stainless steel has a great affinity for oxygen, and will form on the surface of the steel at a molecular level a film of “Chromium Oxide”. The film itself is about 130 Angstroms in thickness, one Angstrom being one millionth of one centimeter."

"This layer is described as passive, tenacious and self renewing. Passive means that it does not react or influence other materials; tenacious means that it clings to the layer of steel and is not transferred elsewhere; self renewing means that if damaged or forcibly removed more chromium from the steel will be exposed to the air and form more chromium oxide. This means that over a period of years a stainless steel knife can literally be worn away by daily use and by being re-sharpened on a sharpening stone and will still remain stainless."


Most of us assume or are under the impression that if a knife steel has at least 12% - 13% chromium in it, it's considered "stainless". So we assume that if a knife’s steel has 14%, 15%, 16% chromium it is sufficiently stainless.

But, there is apparently more to it than that.

Apparently, what makes a steel stainless or at least relatively/reasonably stainless is amount of "Free Chromium".
Apparently, a given steel has to have a certain amount of “Free Chromium” to be sufficiently resistant to corrosion. To some degree, the more “free chromium”, the more resistant to corrosion.

Carbon (the element that makes steel, steel) also has a great affinity for chromium. When a steel is heat-treated to its critical temperature, the carbon combines with the chromium at the ratio of about 1% carbon to 10% (to 12% ???) chromium to form chromium CARBIDES.

The ratio seems to be either debatable, unknown or influenced by other elements (????).

"When chromium combines with carbon in this fashion, it is no longer "free" to provide rust or stain resistance." - *** I have to question this statement as there seems to me to be an obviously higher level of corrosion resistance in steels with say 1% carbon and 4.75%-5.5% chromium (ratio 4.75-5.5 to 1) over say 52100 with carbon at about 1% and chromium at about 1.3%-1.6% (= ratio of about 1.3-1.6 to 1 - noticably lower total chromium and ratio).
If it was only about exceeding the 12 to 1 ratio, then we wouldn't notice any difference between A2 moderate corrosion resistance vs. 52100's much lower resistance to corrosion. There are plenty of other scenarios to draw enough of a "sample" to make a rational case (IMO).

So, I conclude (in my mind / logic) that percentage of chromium "MUST" still be a factor.... not "ratio" alone.

Apparently, “the actual number that metallurgists look at for a steel to be REASONABLY stain/rust resistant is (about ?????) 4% free chromium.”

So, basically, if you have 1% carbon and 14% chromium, you (might) have about 2% “Free” chromium (or something like that. This would be “decent” at resisting corrosion, but obviously the more free chromium there is, the better.

But, it’s not that simple either. There are apparently more than one way to free up more chromium.

Some other elements can contribute in different ways to help a steel be more resistant to corrosion.

Vanadium is also a strong carbide former – Forming Vanadium carbides. When found with chromium, it frees more chromium to render steel more stain resistant. Vanadium also retards grain size during hardening.



Part of this seems to make sense, but part doesn’t (to me).


It seems to me that “free chromium” can’t be the only factor in corrosion resistance. (as mentioned above).
It seems to me that (based on what I have seen with steels with varying degrees of chromium to carbon ratios, larger amounts of chromium are still better than low amounts of chromium at resisting corrosion.

In other words, chromium CARBIDES must attribute towards corrosion resistance in a significant way even if there isn’t a full 1/12 ratio met.

I don’t know if chromium carbides have the same benefits to corrosion resistance as free chromium (chromium oxide). ?????????????

I am curious to know more about chromium carbides vs. chromium oxides. <img src="/ubbthreads/images/graemlins/crossfingers.gif" alt="" />

If you go by ratios alone, INFI “Does” have a high ratio because it has a relatively low carbon content. But, it clearly has a lower percentage of chromium than most steels that are considered stainless (including ATS-34 and D-2).

Actually, based on what I have "seen", it "seems" that the often assumed and discussed standard of simple percentage seems to be more relevant, but I am trying not to be to hasty to assume that is all that matters (?????). - Also, considering Jerry has put a certain emphasis on "ratio". (?????) <img src="/ubbthreads/images/graemlins/confused.gif" alt="" />

INFI (theoretically – and somewhat documented and supported) has 0.50% carbon and 8.25% - 8.5% chromium = about 16.5-17 / 1 ratio – the "Ratio" is actually quite high compared to most steels - even if the actually percentage of chromium is well below 12%.

ATS-34 / 154CM (1.05% carbon; 14.00% chromium) both have about a 13.33 / 1 ratio

D-2 (1.4%-1.6% carbon; 11% - 13% chromium) has about a 8 / 1 ratio

S7 would be about 5.9 to 1

SR-101 would be about 1.45 to one (+/-)

1095 would be about 0 to 1 (lowest ratio for common knife steels)

420 would be about 86.66 to 1 (highest ratio for common knife steels)

Granted 1095 seems the most prone to rust and 420 seems one of the least prone to rust, but 1095 also has 0% chromium, so it is lowest on either scale and 420 has about 12%-14% chromium which although not the highest, the level of carbon VERY low at 0.15%. So, they are extreme in either way of comparing.

ZDP-189 is actually an interesting case study with a VERY high chromium content also has a very high carbon content. So, while it has WAY over 12% chromium at 20%, the ratio is actually well below 12 to 1 at 6.66 to 1 (???????) I have never had ZDP-189 - Anyone know how it rusts???? According to ratios, it should rust about like S7.

S60V and S90V might also be interesting since:

S60V: 2.15% carbon; 17% chromium = 7.9 to 1 ratio
S90V: 2.3% carbon; 14% chromium = 6.09 to 1 ratio

Both also have chromium levels about 12%-13%, but both have (like ZDP-189) the rare case where the percentage is higher than 12%, but their ratio is reasonably lower than 12 to 1.

I have never seen any of my S60V rust. I only currently have one S60V knife, but I have carried it a fair amount. Interestingly, mine was a coated Kershaw Ken Onion Boa. I don't like the coating, but that is the only way Kershaw made the Boa unless you wanted the fruity styled scales - then you could have a satin blade. However, the edge has never showed a single sign of rust. And for the record, the edge is incredibly sharp and I have never needed to resharpen yet. <img src="/ubbthreads/images/graemlins/ooo.gif" alt="" />
The other piece I had, I sold rather quickly and can't comment on.


*** I would be very curious to hear if anyone who might have SDP-189, S60V or S90V has ever experienced any issues with rust and give some feedback. <img src="/ubbthreads/images/graemlins/crossfingers.gif" alt="" /> <img src="/ubbthreads/images/graemlins/thumbup.gif" alt="" />


INFI also has (theoretically) about .36% Vanadium – which should also free up more chromium and further aid (a little) towards helping the chromium content in INFI resist corrosion. INFI also has about 1.3% Molybdenum which is supposed to help resist corrosion a little.

ATS-34 / 154CM both have an exceptionally high level of Molybdenum at about 4%. But, I am not under the impression that Molybdenum is nearly as significant a factor in resisting corrosion as chromium. There are many highly resistant to corrosion stainless steels with a LOT lower Molybdenum percentage. D-2 only has about .7% - 1.2%, all of the 440 steel have about .75% and most other steels of all types are less than 1%. About the only steels in even close to the same Molybdenum ballpark are M2 (4.75% - 6.5%), M4 (5.25%) and BG-42 (4%). There are a handful of others over 1%, but I don’t know the relevance in regards to corrosion.


So, here’s the dilemma:

In spite of what Jerry said, I have seen “Clean” “decarb free” INFI rust - (with my “lying” eyes) much more readily than ATS-34, 154CM or D-2.

WHY????

I am COMPLETELY fine with excepting that INFI rusts. But, it "seems" there is a significant portion of people in denial of INFI's ability to rust. - which I don't understand.
I have "Seen" INFI be more resistant to rust than many others steels that appear MUCH more prone to rust than INFI (such as 1095, 5160, O1, SR-101 and others).

But, I keep reading claims on forums about how resistant to rust INFI is.

Many people seem to view it as I do: INFI is NOT stainless and doesn't act like stainless, but it is pretty darn good and reasonably corrosion resistant for a non-stainless steel. <img src="/ubbthreads/images/graemlins/thumbup.gif" alt="" />


But, I have read where people claim it to be "As Good" as stainless, and throw in stories of how they get it wet, keep it wet, etc. and NEVER see INFI rust. <img src="/ubbthreads/images/graemlins/banghead.gif" alt="" /> <img src="/ubbthreads/images/graemlins/confused.gif" alt="" />

..... I can't buy into those stories. <img src="/ubbthreads/images/graemlins/rolleyes.gif" alt="" /> <img src="/ubbthreads/images/graemlins/confused.gif" alt="" />

I have even seen a small handfull of people try to say similar about SR-101 <img src="/ubbthreads/images/graemlins/rolleyes.gif" alt="" />... Let me assure you = <img src="/ubbthreads/images/graemlins/crazy.gif" alt="" /> <img src="/ubbthreads/images/graemlins/loopy.gif" alt="" />....... <img src="/ubbthreads/images/graemlins/rolleyes.gif" alt="" /> <img src="/ubbthreads/images/graemlins/doh.gif" alt="" /> - SR-101 can rust quite nicely. <img src="/ubbthreads/images/graemlins/wink.gif" alt="" />

SR-101 silly corrosion proof claims aside.....

I would LOVE for Jerry to jump in and help explain or someone else who can try to explain this in layman’s terms. <img src="/ubbthreads/images/graemlins/crossfingers.gif" alt="" />


What is more important and why?:
Total percentage of chromium?
or
Ratio of chromium to carbon?

More information about the comparative relevance between Chromium Oxides and Chromium Carbides would be nice. <img src="/ubbthreads/images/graemlins/crossfingers.gif" alt="" />

- Feel free to mix in some other factors as I know these aren't the only two.

.