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black die looks grey

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  • black die looks grey

    Hello all this is my first post. I'm trying to anodize some 6061 and my black is coming out grey looking. Ph is 5.2 at 140 degrees. Should I check it cold or hot? Could I be anodizing it to long?

  • #2
    Could be a poor connection and the film isn't growing enough or simply not leaving it in the dye long enough. How long is it in the dye? I run my dye temps a little cooler 130 to 135 and it seems to absorb better. If it gets too warm it will start sealing the pores and could lock out before full absorption.

    I haven't run into dissolution problems myself yet so I can't say if you are anodizing too long. What is the part SA and amp specs that you are using?


    • #3
      It's not my connection because all my other colors come out great. I was thinking I was anodizing to long and film was to big maybe. The last price I done was 150 square inches at .7 thickness set at 6.25 amps and 15 volts. Does that seem correct


      • #4
        Running 150sqin at 6.25 amps yields just about 6ASF (amps/sqft). At that current density you should have run for about just under 1.5 hours to get 0.7 mil. Is that how long you ran for?
        Process control doesn't give you good quality, it gives you consistent quality.
        Good quality comes from consistently doing the right things.

        Process control systems for anodizers
        If a post helps you out spread the love and LIKE the post
        Last edited by kevinB: Now. Reason: superfluous typo's


        • #5
          At that amperage you'd need a full 2 hours in the ano tank to have enough depth in the pores for a full black dye uptake.