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Anodising Tank Quickly Overheats

Q. Dear Sir,
I have an anodising tank of approximate 20 litres with lead lining. If I anodise a lot of 1.5 square feet at a time the temperature of bath rises after 10 minutes and I have to chill the solution by immersing ice bottles. This process is very difficult as I cannot control the process. Maximum time of anodising is 15-20 minutes I cannot increase this time due to heat generation.

My question to you is what is minimum tank size required for me if I am to anodise 15 square feet of job per day? Moreover how much time should be given to anodising for good results? For supply I have a DC unit which gives 12 V, 60 Amps. Max with adjustment from 6 Volts onwards with 6 Steps.

Moreover how do I chill the solution. Now I use plastic bottles but this is not convenient. Can I use Aluminium pipe used for antennas of TV. I need your help in this regard as I have come to know that you people are very helpful and you can guide me.

Suprabhat Tambe
- Raipur, Chhattisgarh, India
September 4, 2012

A. Step one is to get a power supply that will put out 18 or 24 volts. Your anodize process at 12 volts is only a bit higher than the rate that the solution is eating the coating. Shorter anodize time = less heat.

With the temperature rising, you are getting a soft anodize. Additives will not help enough to make that practical.

A poor man's cooling system is to get a used CHEAP freezer, modify it so it shuts off at 1 °C. Put a large metal tank in the freezer, fill it with water and pump this water thru a 1/4" polyethylene tubing that is in the anodize tank with the return flow to the freezer tank. You need quite a bit of tubing in the tank. I would use a PVC pipe frame to keep it organized. It will take a day or two for the water to get to 1°C. The tank temps will rise.
Put a valve in the water line to control the volume of cold water and open it up more as the anodize tank temp rises.

It is a very inefficient process, but a lot better than bottles of ice water.

James Watts
- Navarre, Florida
September 10, 2012

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