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reddish tinge in black dye

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  • reddish tinge in black dye

    Anodized our first batch or parts today and for the most part was pretty successful. The only glitch is that some parts seem to have a bit of reddish/brown tinge (dyed black). Any guesses as to cause? The parts were dyed at 110 degrees for 30 mins and then sealed with the high temp sealer.
    Also will finger shaped projection anodize heavier than other surfaces... like the same shapes tend to plate heavier?

  • #2
    Try dyeing at 140 deg. F, also be sure the dye is very THROUGHLY mixed.

    As a chemical engineer at US Color likes to say; there is no such thing as black dye. Black is a combination of at least 3 other colors, ratioed to cancel each other out. (One of them is red.)

    You can eliminate any possible effects of the sealer by using boiling water to seal as a test.

    The anodize thickness should be uniform over all surfaces, Having no or not enough agitation will cause an uneven coating (the most likely cause).

    Increasing the distance between the work and the cathode(s) can sometimes fix this, assuming you have adequate agitation.


    • #3

      Again thanks for the expertise and advice. That was my first suspicion(temp too low).
      I had read a few things about boiling water sealing in regular CD anodizing.. It works with LCD?
      Another prob might have been that we mixed the dye at about 100 degrees and I noticed afterward it should be mixed at 180!


      • #4
        I regularly use boiling water to seal LCD, an old habit. Make sure the water is boiling hard, it should not stop boiling when you put in the work.