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Having trouble with anodizing black please help

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  • Having trouble with anodizing black please help

    I got my lcd anodizing kit from caswell and started anodizing green and it looked great everything went well. But when i went to do black they turned out horrible. They were dull looking with a red tint to them. So i called up caswell and he said that i wasnt anodizing them long enough. The first time i did it for about 45minutes. So i tried letting them sit longer for about 2 hours and they were a little better they were black but still really dull. I took some wd-40 and sprayed it on and that helped alot they look alot glossier but is there anything i am doing wrong or has someone had this problem. The parts start of with a good finish they are machined so its not the surface.

  • #2
    how are you cleaning/degreasing the parts beforehand? Are you following the LCD instructions verbatim? What type of power supply are you using, and what current density are you running at? The more information you provide, the more answers you'll receive.


    • #3
      I clean them with distilled water and put them in the desmut solution.
      I use the rectifier the kit came with nd try to get the amerage to the 4.5amps per cubic foot although its kind of diificult to get it exact how do you guys go about doing that?


      • #4
        If you're not getting the same current density from one time to the next, your results will definately be different each time. Make sure you calculate the area of the part first, then calculate what current you will need to run at 4.5 Amps/ft^2. For example, if you're anodizing a part that is 50 in^2:

        (50 in^2) *(1ft^2/144in^2)*(4.5 A/ft^2) = 1.5625 Amps.

        If you have a CC power supply, simply set the current the the above calculated value. Let it anodize for 90 minutes and watch/record the voltages about every 2-5 minutes. Make a graph of Voltage vs. Time (if you want) and you'll easily see when PAR was reached. Once you do this a couple of times for your system, you'll be very comfortable with what the voltage readings should be and you'll see very repeatable results time after time.


        • #5
          I'm not familiar with Caswell's rectifiers, but there are a couple things either omitted or not fully explained.

          When asked if you are degreasing, you state you washed in distilled water and then used the de-smut on it. If you are not degreasing it, then that would contribute to the problem. De-smut is not a degreaser, so it is important that the part also be properly and completely degreased.

          Next is that LCD is not based on time, it is based on reaching the peak voltage. Using the power supply, you have to watch the voltage rise, and when it starts to drop you would remove the part from the electrolyte. If you based your anodization on time, there is a likelyhood that you either didn't anodize for enough time, or you exceeded the time and the acid began to eat away the surface had grown, or had opened the pores so that they were so large they didn't hold the dye completely.

          To get a more accurate answer, you'd have to include the size of the piece in sq feet, the amperage setting (not the current density), the peak voltage attained, the length of time it took to reach peak voltage, how long after reaching peak did it remain in the electrolyte, and the voltage when removed from the tank. Also helpful would be the temp of the electrolyte and the dye temp.


          • #6
            I'm starting to wonder if it is the dye. What black die do you guys use?


            • #7
              I use the HBL black from caswell and sometimes BK Excel Black. Make sure you're keeping your dye sealed when not in use. I had problems with my black dye when I left it out unsealed for a couple days. Mixing a new batch and keeping it sealed eliminated these problems.


              • #8
                So do you get a bright finish with those dyes or is it dull?


                • #9
                  The dyes are capable of a very nice gloss black, but the part has to be smooth before anodizing, and you need to have a good anodize layer also. The part below is a machined finish, but it looks like polished lacquer. Buffing, or bright dipping (chemical polishing) the part before hand gives similar results. If the part is dull or rough before anodizing, you will have some sort of a satin or flat surface.

                  Here is a link and a photo of 2 parts done by me with the dye sold by Caswell's. It is hard to capture the depth and brilliance of the finish in a low-resolution .jpg so the parts look better in person than here.