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Evaporust revisited

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  • #61
    Phosphoric, electrolytic derusting, vinegar, etc all demonstrate some "stress corrosion" effects. So far, the Evaporust shows very little effect. Phosphoric darkens the steel and changes the surface to an iron and phosphorus compound.

    The stress corrosion process involves the electrolyte corroding the steel away preferentially where there are stresses in the steel. The corrosion releases some stress, but that release concentrates it at the bottom of the corrosion pit, which then becomes bigger as the more concentrated stress encourages more corrosion. Even electrolytes which are normally pretty benign seem to get activated where there is stress.

    Case hardened parts seem to be very susceptible. The corrosion pattern resembles the color patterns on "color case hardened" parts.

    Evaporust seems to contain no phosphoric acid.
    CNC machines only go through the motions

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    • #62
      Originally posted by J Tiers View Post
      Evaporust seems to contain no phosphoric acid.
      It wouldn't surprise me if Evaporust was mainly a bit of tannic acid. The same thing you get from submerging old leaves. There was a guy on the smokstack old engine forums some years ago, who derusted an entire farm engine by submerging it in a pond under a tree for a year. Took it out, wiped the black stuff off, and everything moved like new. Cleaned it right up.

      I have heard similar claims for molasses in water as a chelating agent, but never tried it.
      25 miles north of Buffalo NY, USA

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      • #63
        Originally posted by nickel-city-fab View Post

        It wouldn't surprise me if Evaporust was mainly a bit of tannic acid. The same thing you get from submerging old leaves. There was a guy on the smokstack old engine forums some years ago, who derusted an entire farm engine by submerging it in a pond under a tree for a year. Took it out, wiped the black stuff off, and everything moved like new. Cleaned it right up.

        I have heard similar claims for molasses in water as a chelating agent, but never tried it.
        Tea leaves. That should be easy to try on a small scale test.

        JL.............

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        • #64
          Originally posted by dian View Post

          its a czeque product, no idea how they sell it and where.

          this little addapter has been sitting in it overnight. beautifull finish, didnt attack the steel whatsoever. compared to wrist pins i left overnight in phosphoric (15-20%) unintentionally. would be great for painting but otherwise they are ruined. both had some light rust pitting.

          i tried mixing phodsphoric with some solvents but didnt get comparable results. they must have something in there that protects the steel.
          The MT adapter looks nice. The wrist pins, not so. I've had phosphoric acid (navel jelly) turn steel black. I have a small bottle of it that's been setting on the shelf for years. I've had little use for it an even less luck when I did use it.

          JL..............

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          • #65
            Originally posted by nickel-city-fab View Post

            It wouldn't surprise me if Evaporust was mainly a bit of tannic acid. The same thing you get from submerging old leaves. There was a guy on the smokstack old engine forums some years ago, who derusted an entire farm engine by submerging it in a pond under a tree for a year. Took it out, wiped the black stuff off, and everything moved like new. Cleaned it right up.

            I have heard similar claims for molasses in water as a chelating agent, but never tried it.
            I have used tea leaves on steel. It was to blacken the steel. Worked fine for that, no effect otherwise.

            I could not tell you if E-R has it, but E-R does not turn steel black.
            CNC machines only go through the motions

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            • #66
              Some organic acids like citric or tannic would be chelates, but may also work as weakish acids. Many people think that ER is based on EDTA. That would be consistent with what they say in their literature, but they also claim to have sulfur compounds to extend the life of the chelate.

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

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              • #67
                they use coffe to blacken/etche knives. i guess tea would be similar.

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                • #68
                  The reaction of iron with various tannins is pretty well known. There are some methods for blackening oak and other tannin bearing woods using iron filings or steel wool. Ammonia enhances the effect.

                  You can see the effect around ferrous fasteners in oak, especially if it gets wet. Using ferrous clamps when gluing oak with water based glue can leave black stains on the wood.

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

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                  • #69
                    About evaporust on large pieces, you can soak those thick blue paper towels in evaporust and use magnets (or gravity, if magnets don't work on your aluminum) to stick them to the workpiece. This won't soak into all the nooks and crannies like a bath will, but if you're doing something that's been disaeembled, like a casting, it works fairly well. Change out the towels when they dry out or become rust-colored.

                    Regarding the glass-vs-plastic, I have had hit-or-miss results using ziploc bags. Hadn't thought of glass - might try a few cigar tubes in the basket for tstuff like drill bits, and if that works out hit good ol' sciplus for some better options.

                    Originally posted by J Tiers View Post
                    I have used tea leaves on steel. It was to blacken the steel. Worked fine for that, no effect otherwise.
                    Easy thing to try out, that and the coffee grounds. Heated or not? Open-air (as opposed to trapped in a ziplock or jar)? Overnight, or one of those leave-it-for-a-week molasses jobs?


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                    • #70
                      Originally posted by thin-woodsman View Post
                      .........

                      Easy thing to try out, that and the coffee grounds. Heated or not? Open-air (as opposed to trapped in a ziplock or jar)? Overnight, or one of those leave-it-for-a-week molasses jobs?
                      Overnight, not heated particularly. Needed some hardware blackened by the next day so we could ship a show sample. No time to get any tool black. It worked, but the show was in Chicago, in McCormick place, and we found out that the treatment was not protective against rust when the humid air off the lake rusted it.
                      CNC machines only go through the motions

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