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Thread: It's all going to rust, isn't it?

  1. #16
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    Quote Originally Posted by Stanley Covington View Post
    Have you read test results, or made your own investigation of the corrosion resistance of PM-V11? I have not used it, and so cannot comment, but I know from experience that Hitachi's ZDP-189, which contains around 20% chrome, is not as rust resistant as many tool steels with less chrome. My point is that high Chrome content is not a guarantee of corrosion resistance.
    I own a lot of PM-V11, though I can't say that I've really stressed its corrosion resistance. I live in California and am a fanatic about corrosion-proofing. My statement was based more on knowing the identity of the alloy and its well-established reputation in the knife world.

    No steel is truly rust-proof, it's just a matter of degrees. That's why I said "very corrosion resistant" instead of "corrosion-proof" or something like that.

    For classification purposes the line between stainless and not is drawn at 10% *free* Chromium, meaning Chromium that is in the metal matrix rather than bound up in carbides. As an example, D2 has 12% Cr and is *not* stainless because >2% Cr is in carbides. A steel down at that bare minimum won't be as corrosion-resistant as one with higher free Cr (and there are a bunch of additional variables such as ferritic/austenitic/martensitic), but they had to draw the line somewhere.

    As far as anybody has been able to tell via XRF, PM-V11 is Carpenter CTS-XHP, which is a "true" stainless with 16% Cr. I don't know (and can't remember how to estimate) the percentage of free Cr, but the fact that Carpenter bills the alloy as stainless means that it's a safe bet that it's in excess of the 10% threshold. In terms of reputation, it's known to rust more than the most resistant stainless alloys, but less so than ZDP-189 and far less than non-stainless steels.

    ZDP-189 has 3% Carbon IIRC, which means that a fair bit of its Cr will end up in carbides rather than in solution, so that's probably one of the reasons why it performs on the low end of the stainless range in terms of corrosion resistance. With that said it's still a lot more corrosion resistant than typical tool steels.
    Last edited by Patrick Chase; 11-12-2017 at 4:34 PM.

  2. #17
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    Sorry about the double-reply, but I wanted to take this part separately...

    Quote Originally Posted by Stanley Covington View Post
    It is absolutely true that VCI's only work in enclosed containers. Is that a viable storage condition for you?
    They don't have to be fully enclosed, for example the VCI impregnated mats work pretty well in typical tool chest drawers with "leaky fronts". You have to change them every couple years, but that's about it. Your point about contaminants is right on - the metal surfaces need to be clean for VCI to work, and if you're going to clean you'd might as well slap on some 3-36 while you're at it :-)

    Quote Originally Posted by Stanley Covington View Post
    All oils are liquid (until they aren't) and evaporate over time leaving steel unprotected. Some last longer than others, and are more resistant to oxidation. Vegetable oils oxidize relatively rapidly, and can even turn acidic as they become rancid. So you need a liquid oil, something easily and quickly applied, very stable, and petroleum based (ergo synthetic motor oil), for daily constant use as both lubricant and surface protectant.

    And you need something that is easily applied but that displaces moisture and then seals the steel from surface moisture when you are not using the tools. Paraffin wax is a proven sealant that does not readily oxidize or evaporate, and is pretty neutral. But by itself, it will not displace water. SG. Boeshield is paraffin wax with a solvent carrier of some sort. In my experience, it is not good for displacing moisture. CRC 3-36 is also paraffin based, but the solvents it contains do make the spray displace moisture, so I recommend it.
    The thing with Boeshield is that the non-wax components are all volatile, and once those flash off you're left with a thin coating of dry wax that is easily damaged/removed by handling. The nonvolatiles in 3-36 remain in a "sludgy" liquid form after the solvents flash off, and can "flow" a bit to fill scuffs etc. My experience with the two is similar to yours: 3-36 works much better in practical applications where handling is an issue.

    Quote Originally Posted by Stanley Covington View Post
    CRC SP-400 is some sort of wax too, but it dries into a solid skin that is very effective, but more difficult to remove.
    SP-400 is the same idea as Boeshield, but with a more durable wax that is much more resistant to both handling and removal/cleaning. I only use it if I'm going to store something for a while. It's very effective for that, though.

  3. #18
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    As someone who resides in a coastal town, my recommendation would be SilberGlide.


  4. #19
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    Quote Originally Posted by Patrick Chase View Post
    As far as anybody has been able to tell via XRF, PM-V11 is Carpenter CTS-XHP, which is a "true" stainless with 16% Cr. I don't know (and can't remember how to estimate) the percentage of free Cr, but the fact that Carpenter bills the alloy as stainless means that it's a safe bet that it's in excess of the 10% threshold. In terms of reputation, it's known to rust more than the most resistant stainless alloys, but less so than ZDP-189 and far less than non-stainless steels.
    One way to get a very rough handle on this is to look at the amount of Carbon available to form carbides, assuming that the matrix is uniformly eutectoid. The Cr carbide found in steels is Cr3C2, which contains 6.5 times as much Cr as C by mass.

    CTS-XHP has 1.6% C, of which ~0.8% is in the matrix and the remaining ~0.8% is available to form carbides. Even if all of that formed Chromium carbide rather than carbides of other alloyants it would only bind 5.2% Cr, leaving 10.8% free. It would appear to be a legitimate stainless.

    This sort of rough analysis hints at why ZDP-189 has marginal corrosion resistance. It has 3% total carbon, of which ~2.2% is available to form carbides. That much Carbon could conceivably bind up to 14.3% Cr (again depending on what specific combination of carbides forms), leaving 5.7% free. I don't think that's actually what happens, though somebody who knows far more metallurgy than I would have to clarify that. Does Hitachi advertise it as stainless?
    Last edited by Patrick Chase; 11-12-2017 at 7:12 PM.

  5. #20
    Quote Originally Posted by Thomas L Carpenter View Post
    What is an oilpot and how is it used?
    Thomas,
    My "oilpot" is a rag saturated with Boeshield and Johnson's wax dissolved in turpentine so that it is somewhere between tacky and damp. I use turpentine because it does not evaporate as fast or as completely as MS and I like the aroma. This rag sits in a very small plastic food container with a snap on lid. I have three of them, located in each location where I keep chisels or planes. I give each tool a wipe before I put it away. When I go back to use the tool again it is not oily and does not need to be wiped off before use.
    (I probably don't need to do this in Colorado but it's a habit that I acquired in Florida. The salt from my hands really promoted rust.)
    Doug

  6. #21
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    Quote Originally Posted by Patrick Chase View Post
    One way to get a very rough handle on this is to look at the amount of Carbon available to form carbides, assuming that the matrix is uniformly eutectoid. The Cr carbide found in steels is Cr3C2, which contains 6.5 times as much Cr as C by mass.

    CTS-XHP has 1.6% C, of which ~0.8% is in the matrix and the remaining ~0.8% is available to form carbides. Even if all of that formed Chromium carbide rather than carbides of other alloyants it would only bind 5.2% Cr, leaving 10.8% free. It would appear to be a legitimate stainless.

    This sort of rough analysis hints at why ZDP-189 has marginal corrosion resistance. It has 3% total carbon, of which ~2.2% is available to form carbides. That much Carbon could conceivably bind up to 14.3% Cr (again depending on what specific combination of carbides forms), leaving 5.7% free. I don't think that's actually what happens, though somebody who knows far more metallurgy than I would have to clarify that. Does Hitachi advertise it as stainless?

    Patrick:

    Thanks for the insight. It explains a lot.

    Hitachi does not advertise ZDP-189 as stainless but as a tool steel. It is much more corrosion-resistant than HC steel, but less so than some others, like 440C. It gets very hard at 66~67Rc, and cuts very well, but has problems with brittleness, so they often laminate/sandwich it with the more flexible and corrosion-resistant ATS34 to make a rikizai for kitchen knives. A bitch to shape even pre-hardening. It does not make a good dive knife.

    Stan

  7. #22
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    Quote Originally Posted by Stewie Simpson View Post
    As someone who resides in a coastal town, my recommendation would be SilberGlide.
    From glancing at the SDS and the manufacturer's site this appears to be a pretty standard microcrystalline hydrocarbon paste wax along similar lines to Heritage Wax. Those work perfectly well to provide a barrier against corrosion, with the caveat that they don't penetrate like Boeshield, 3-36, SP-400, etc.

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