Rust removal from gage pins (yes, I know :))
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  1. #1
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    Default Rust removal from gage pins (yes, I know :))

    One of my .752"-.832" gage pin sets has some rust with minor pitting at one end of the pins. This set is not used for anything super precise, and the opposite 2/3 of the body end is in a perfect shape.

    I tried using phosphoric acid for the affected end, but it makes the surface dull grey. First of all, I wonder why. I know that Evaporust or phosphoric acid solutions remove oxides. But what's on the surface of a regular gage pin to become dull? Isn't it just a ground steel?

    Any other methods you'd prefer, or you just wouldn't worry about dull appearance? I assume that using phosphoric acid is less detrimental to the pins (vs. use of any abrasives, even the mildest ones like white scotch Brite, buffing, etc.)

    P.S. Yes, I certainly understand that rusted gage pins are thrown away and replaced. But this particular set is sufficient for my modest homeshop tasks.

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    Always have to brush off the dull grey with a small brass or SS brush. Nothing else works better.
    For your gauge pin sounds like you don't want that method.

    Use a battery with electrodes in a soda bath. It will accentuate the pits but all the rust will be gone.

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    Quote Originally Posted by MichaelP View Post
    One of my .752"-.832" gage pin sets has some rust with minor pitting at one end of the pins. This set is not used for anything super precise, and the opposite 2/3 of the body end is in a perfect shape.

    I tried using phosphoric acid for the affected end, but it makes the surface dull grey. First of all, I wonder why. I know that Evaporust or phosphoric acid solutions remove oxides. But what's on the surface of a regular gage pin to become dull? Isn't it just a ground steel?

    Any other methods you'd prefer, or you just wouldn't worry about dull appearance? I assume that using phosphoric acid is less detrimental to the pins (vs. use of any abrasives, even the mildest ones like white scotch Brite, buffing, etc.)

    P.S. Yes, I certainly understand that rusted gage pins are thrown away and replaced. But this particular set is sufficient for my modest homeshop tasks.
    Tumble with walnut shell & rouge media, mayhap?

    Chemicals and 'lectricity would not be on my radar for "gage"-anything, even "hobby" use. I'd aside 'em for use as "project metal" first.

    Used-but-good, or new and cheap sets are plentiful enuf, if your one is too badly bonked.

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    You might go to you tube and look at Adam Booths vids, he uses a rust removal chemical, that works a treat on cutters. The name eludes me but contact him to find out what is.

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    the gray coating is phosphate. no good on a precision surface. rust converts before the coating appears with phosphoric. you have to find the right immersion time depending on concentration and temperature. take it out, brush and repeat maybe. if you try evaporust or molasses make sure the whole part is immersed, you get a parting line otherwise.

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    Phosphoric acid will convert rust while evaporust is a chelating agent which removes it. Choose yer poison. The good news is that evaporust doesn't degrade the nonrusty parts, but be sure to completely submerge the pin.

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    Thank you everyone.

    After some experimenting, I went with Evapo-Rust and, per MrStretch's recommendation fully submerged the pins: partial submersion produced a grey ring at the liquid-air level. Held them in overnight with a pretty good result. There is some grey spotting here and there (not only on the rusted areas), but you cannot compare it with the effect of phosphoric acid where the whole surface became grey totally hiding the size marks.

    No apparent pin diameter changes after either of the methods though.

    After soaking in Evaporust, I wiped and oiled the pins. No attempt was made to wash Evaporust out prior to drying.
    Attached Thumbnails Attached Thumbnails gage-pins.jpg  

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    I’ve used evaporust with success as well (for shop grade). Unfortunately it removed the markings that indicate pin size. Kind of annoying but better than rust.

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