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

[Patrick Chase]

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.