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Black anodized aluminum inconsistency

I am having some difficulty with my plating shop and its inconsistency in providing me with a consistent color or tone of a flat black hard anodized aluminum tube. Can anyone suggest an efficient method for testing the black ink tank. I am suspicious of its content.

Regards,

Greg Burns
Industrial, military, aerospace - Mesa, Arizona
2003

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Your dye supplier should furnish occasional dye analysis services. The one I work for does. Constant color shade control depends on constant control of many variables more often occurring at the anodizing tank rather than the dye tank:Acid Concentration, Dissolved aluminum,agitation, current density, voltage, temperature, time, impurities. Then the rinsing between the anodizing and dye comes into consideration. Then the dye parameters like: time, temp, concentration, impurities, make-up water, is the tank stainless or plastic. To get specific you need to give us more data or live telephone talk.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

2003