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Re: Anodizing calculations (720 Rule)

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  • Re: Anodizing calculations (720 Rule)

    We have started to do anodizing at our job with mixed results. First I am having trouble keeping my anodize tank between 68-72 degrees. What are you doing out there to keep your temp down. I have a 50 gallon tank with a titanium rack that can hold up to 60 pcs. I have tried both constant voltage and the constant current. Both seem to heat up the tank beyond the good range. My clear anodize looks good but I am having a tough time with the black dye. It seems to come out streaky, dull and chaulky. Any suggestions would be appreciated.


  • #2
    Re: Anodizing calculations (720 Rule)

    How big are the parts?
    What kind of agitation does the tank have?
    Are you going by the 720 rule?
    How high does your tank temp get to?

    The streaky, dull, and chaulky can be caused by a number of things. Dissolution, rinsing in tap water, old sealer among others.

    My tank is only 20 gallon. For now I am running a window unit into a cooling box. Some of the others I have talked to are using homemade heat exchangers or saltwater aquarium chillers with Ti cores. A chiller big enough for your tank would be very pricey. SS
    Last edited by sswee; 11-14-2005, 09:34 PM.


    • #3
      Re: Anodizing calculations (720 Rule)

      Parts range from small blocks to flat plates several inches long and wide.

      Tank has plastic air hose with holes in it.

      We are using the 720 rule.

      It has reached 80 degrees before. Usually hits 76 to 77

      We are using distilled water for rinsing. It may be the sealer. We have had to add 5 gallons of distilled water due to evaporation about every two days. Do I need to also add sealer? With the black dye the sealer has also turned a dark color. Will this affect my clear anodize parts that do not get dyed?

      We too are running a window unit but are not able to keep the heat down. I can get the temp down to 68 if I run the unit for a couple hours before running the parts but withing an hour to hour and 1/2 it is up in the middle to upper 70's.

      After I dye the parts and apply the sealer the parts look very black and shinny. After they have dried they are chaulky looking and dull. I wipe them with a cloth and some of the dye rubs off? Parts also look streaky.

      I know what you mean on the cost of the chiller.



      • #4
        Re: Anodizing calculations (720 Rule)

        It sounds like dissolution but if that is it, your clear parts should have a chalky residue also. If the tank temp is getting to the high mid 70's the pocket of heat around the part is higher leading to dissolution. What CD are you running?

        You said apply the sealer. What kind of sealer are you using? Old sealer will cause a residue if you're using nickel acetate but it won't cause the color to rub off with it.

        The first thing I would do as far as upgrades would be a pump to circulate the electrolyte. It made a world of difference on my 20 gal. tank. No acid mist to deal with and evens out the temp in the tank. It was the most cost effective for the benefit it produced. The other thing on a pump is that later if you decide on a chiller, you'll need the pump. I'm using a Little Giant 3-MD-HC with 720 GPH. They are not cheap but no where as pricey as a chiller.


        • #5
          Re: Anodizing calculations (720 Rule)

          I have problems like you described when going over 70F. If you are getting dye in the sealer, that is most likely an indication of desolution.
          Also, please tell us the CD you are using (amps per sq. ft Curent Density), the duaration of the runs, and if you are using shorter run times for the clear.
          I'm one of the guys using a homemade chiller using PVC pipe and a pump. I made mine for about $100, but I'm taking a chance using a non acid-rated pump (I'm on my second pump now).
          Finally, with the sealer, yes, just add water as it evaporates.
          I watch the sealer, and when it becomes milky, it's time for a new batch. It can be filtered through a coffee filter, but when it goes bad, the milkyness does not filter out.
          I do things.