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Does Agitation causes Alodine T5900 Concentration difference in Chromate Dip Tank

We use 15.5 X 3.5' dip tank on floor to chromate coat our aluminum parts and just noticed recently that the concentration of the Alodine T5900 is doubled on the agitator end than the other end of the tank. We try to figure out the reason and possible solution for this issue. Thanks!

May Chen
Process/Manufacturing Engineer - Whitby, ON Canada
June 28, 2011

If your agitator is not doing a good enough job, then there will be concentration differences. We use T5900 here at our shop (albeit its a 3' by 3' tank) without too much trouble. Agitation is very vital because you have to keep the pH between 3.8 and 4.0. When you have to raise the pH you use the T5900 toner (which is potassium hydroxide) and that precipitates some of the metal out of the solution. So if your solution isn't well agitated, some locations in your tank will have higher concentrations than other due to the settling of the precipitate. Hope this helps.

Geronimo Cebrero
- Oxnard, California
July 5, 2011

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July 8, 2011

Thank you very much for the answer.

Here is another concern:

How do you to determine the tank's life expectancy? Do you know any specialist for the Dip Tank?

In our plant we usually clean the Alodine Tank every 4-6 weeks:

Stop the agitation 16 hours and then pump out the solution, clean all dirty on the bottom off the tank and then pump the solution back.

We've run the tank for more than one and a half year with this way.

Thanks again.

May Chen
- Whitby, Ontario, Canada

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