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Curious about CD

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  • Curious about CD

    I am not having a problem with CD but too much time to think while running parts. After reading most of the posts and having started with a battery charger the question arose to me, What effect does CD variation have on pore size? If you run a part at 6 ASF for 1/3 to 1/2 of your run time, then 4.5 ASF to completion, does the pore size change. One part I ran had the surface area miscalculated, causing the part to run at a higher CD than intended. This lead to the CC PS to run to its voltage limit and start dropping current. The current went back up to its preset at the end of the run time. The part dyed fine with no apparent problems. This also made me wonder what happens to the pore size during current variation. Does anyone know? Good thing I'm no cat.

  • #2
    It sounds like your ready to take the next step.
    Many others here intend their anodizing for commercial purposes and need to increase the throughput by decreasing anodizing time. Once you have LCD figured out you have the knowledge to modify the anodizing process and stay out of trouble.

    If you plug different values for current density into the 720 Rule you will see the relationship between CD and anodizing time for a given coating thickness.

    Higher CD reduces pore size, but the CD can be increased substantially before you will experience dyeing difficulties. Agitation and cooling play a large part.

    Varying the CD during anodizing distorts the pores; sometimes this is done delibrately for special applications, but generally a uniform pore will provide the strongest and best looking anodize layer.

    Our very own M_D has modified LCD substantially to suit his own commercial application, and so have many others. Once the basics (LCD) are understood Caswell and I encourage this practice, but not until you do know what's going on. The bulk of hobby anodizers stick with LCD as it stands; if throughput is not an issue, modifying LCD won't buy you much.


    • #3
      I know you have posted the info a few times, but I cannot find the detailed post again on your cooling/recycling system for your tank. In Texas the temp goes from one extreme to the other so fast its hard to stay up. Last week I had to put in heaters to get the temp up and now I need to go the other way. All I have been able to find again is a 1/4 HP modified aquarium chiller with a 420 GPH pump. I have located a saltwater aquarium recirculation pump that is a little higher GPH(500+) with ceramic shaft. Do you think this and a chiller would work? My tank holds 15gal with about 4" to the top of the tank. A fan hasn't done much good. Thanks again.


      • #4
        Go look at the 2nd. page of the 3rd. sticky ("A quick question...").

        You do want an acid rated pump (rated by the manufacturer as sulfuric acid safe) and a chiller with a one piece titanium tubing circulating coil.

        For your 15 gals. I think a chiller in the 1/2 HP (or larger) range would be appropriate, especially in a Texas July.