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Dye problems with bead blasted finishes

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  • #16
    If your parts require some sort of wetting agent (like WD-40) to be the right shade you have a problem, beadblasted or not. Most of my work is beadblasted (for the matte texture) and they look just as they should when they're dry, no wetting agents, no excuses.

    What you are describing are the usual symptoms of excessive dissolution. This can be caused by any of the following:

    1. Too high an electrolyte temperature.
    2. Wrong current density for the electrolyte concentration.
    3. Wrong anodization time.
    4. Poor cleaning and/or native oxide removal.
    5. Bad electrical connections.

    What your brother did on a key chain is hardly proof, did these beadblasted parts have the same (or nearly the same) surface area as the keychain? If the answer is no, the keychain is irrelevant.


    • #17
      My latest part was 6061, had roughly 7sq in, the electrolyte was at 70* and was drawing 1 amp. The time shouldn't be the problem because I ran it 3 times before the dye even took(increasing time each trial by 15 min), so I don't think it was in there for too long. I washed it with hot detergent water and a tooth brush, used Caswell Deox/Desmut for 2 minutes. Strait to anodizing after a good rinse. Dye tank for 15-20min.
      A connection may have been weak but the amperage was consistent through the time and it seemed on par with what a comparable sized part drawls in my setup. I seem to only have problems with bead blasted parts.

      I'm going to connect to the cathodes in a little different manner a.s.a.p. to see if that helps. Now it is alligator clamp connections crimped to aluminum wire (all contacting surfaces cleaned and deoxidized prior to crimping).


      • #18
        Anodizing a 7 square inch part at 1 amp is about 20 amps current density for a smooth part. When they have a rougher texture, it is probably safe to add 15-20%, or maybe more for the actual surface area.

        I don't have time to review the whole thread to see what details you have provided so far, but that's too much current unless you have a strong acid concentration. Assuming that you did have the proper electrolyte concentration, 20 amps CD should finish a typical anodizing job in about 20-25 minutes.

        With parts that small, you need to be able to accurately control the current, as just a tenth or two error throws it off a lot, percentage wise.