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  • #16
    did you have to take the lid of that pot again?

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    • #17
      Originally posted by MattiJ View Post
      + anything that has sharpened edge or is (was?) hardened would be suspect to hydrogen embrittlement in electrolytic cleaning. Same problem with acids.
      This is repeated over and over and over and over. It has been repeated so often "that everyone knows it". And I certainly am not denying it.

      Has anyone actually done any testing to see to what degree this occurs? Is there any reference for it?

      It makes sense, as there can be electrolysis of the water, and that end at the object to be de-rusted will be where the hydrogen goes to accept electrons. With a larger concentration of hydrogen around the object, diffusion into the metal is possible.

      The question is whether it becomes a significant issue in the time needed for de-rusting. There must be some depth to which the diffusion reaches in a given time.

      And, if so, why would a post-treatment baking not drive out the hydrogen?
      Last edited by J Tiers; 11-14-2017, 11:30 AM.
      CNC machines only go through the motions

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      • #18
        Originally posted by MattiJ View Post
        + anything that has sharpened edge or is (was?) hardened would be suspect to hydrogen embrittlement in electrolytic cleaning. Same problem with acids.
        Any lathe or mill cutters are not getting the bath. When needed I am scotchbriting the shanks clean, then trying them out .
        If they are trash, into the Chinese recycle bin they go.

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        • #19
          Originally posted by J Tiers View Post
          This is repeated over and over and over and over. It has been repeated so often "that everyone knows it". And I certainly am not denying it.

          Has anyone actually done any testing to see to what degree this occurs? Is there any reference for it?

          It makes sense, as there can be electrolysis of the water, and that end at the object to be de-rusted will be where the hydrogen goes to accept electrons. With a larger concentration of hydrogen around the object, diffusion into the metal is possible.

          The question is whether it becomes a significant issue in the time needed for de-rusting. There must be some depth to which the diffusion reaches in a given time.

          And, if so, why would a post-treatment baking not drive out the hydrogen?
          Plenty of references if you check google for it. I have only personal experience from one plane iron that seemed to lose ability to hold edge after derusting. But truth to be told I can't remember how good it was even orginally 15 years ago.
          http://www.misumi-techcentral.com/tt...-pickling.html

          Bake should work if you choose to do it.
          Location: Helsinki, Finland, Europe

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          • #20
            Originally posted by MattiJ View Post
            Plenty of references if you check google for it. I have only personal experience from one plane iron that seemed to lose ability to hold edge after derusting. But truth to be told I can't remember how good it was even orginally 15 years ago.
            http://www.misumi-techcentral.com/tt...-pickling.html

            Bake should work if you choose to do it.
            They give a "rate", but it is not clear what the "rate" means in actual change in material properties. After all, that is the real issue. I did google it......

            As for baking.... Dunno about that "" you sort of HAVE to do the baking, or not clean/put up with rust, or have fragile steel.

            The common zinc-electroplated "drywall screw" is an example of what happens with a rough plating process and absolutely no care taken to deal with embrittlement. At last I assume so, since the standard ones do not break, but plated ones from the same manufacturer have broken off as much 3 times out of 5 when driving them (they are somewhat better now).

            A blade that does not hold an edge.... in what way? does it dull? Or does the edge break off and chip? If it chips off, that is evidence for embrittlement, but if it just dulls, there is more chance that it is just softer steel.
            Last edited by J Tiers; 11-14-2017, 01:34 PM.
            CNC machines only go through the motions

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            • #21
              Originally posted by J Tiers View Post

              A blade that does not hold an edge.... in shat way? does it dull? Or does the edge break off and chip? If it chips off, that is evidence for embrittlement, but if it just dulls, there is more chance that it is just softer steel.
              Chips off.
              Location: Helsinki, Finland, Europe

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              • #22
                Fair enough.

                Throw it in he oven and see if that helps. If so, then you have GOOD evidence.
                CNC machines only go through the motions

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                • #23
                  There is an ASTM standard for baking after electroplating, but I'm not sure how well it applies to electro de-rusting.

                  The standard requires baking at 190 degC for at least 3 hours for steels of 1200 MPa or higher.

                  Low strength steels aren't really susceptible to hydrogen embrittlement.

                  Ed
                  For just a little more, you can do it yourself!

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                  • #24
                    Originally posted by Glug View Post
                    The problem with using electrolysis on the mystery metals you described is some of them will probably contain cadmium, chromium, nickel, and other metals. Those will end up in the solution, and I think they call that Hexavalent Chromium. That's very bad stuff, and it is verrry difficult to dispose of properly.
                    Flunked chemistry, did you?

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