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Variability in Finishing Voltage and Thickness when Anodizing 6061 at Constant Current

I looking to better understand why I would see very different oxide thickness for the same part made from 6061-T6 (2.0 mils vs 2.7 mils) when anodizing by constant current (and time). For my 2.0 mil run, the sample was processed at 62 amps and finished at 48.5 volts, for my 2.7 mill run, the sample was also processed at 62 amps but finished at 91.25 volts. Peak voltage was achieved at about 36 minutes. The overall run was programmed for 56 minutes. This is a standard hard anodize line using a sulfuric acid electrolyte

David Hammerich
- Phoenix, Arizona, USA
November 5, 2009

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First of two simultaneous responses --

Better solution agitation or better temperature control or better contacts on the higher end voltage one.

James Watts
- Navarre, Florida
November 6, 2009

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Second of two simultaneous responses --

David

If your current, time, and surface area are the same, you should expect the same thickness. Some possibilities that come to mind for the variation include inaccurate measuring devices/methods, and different rack material if you are using Aluminum.

Willie Alexander
- Colorado Springs, Colorado
November 6, 2009