Letter 27033

Constant current vs. voltage anodizing  

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There is an equation that tells a person if they are anodizing using constant current as opposed to voltage anodizing, the time it would take to acheive various thicknesses. Can you share this with me?

Thank you,

Edward f. Yost
line operator quality control - Ramsey, MN, USA

Anodizing is theoretically by Current Density. I know a lot of anodizers that these many volts at this much time on this type of alloy will get you this thickness of coating; these numbers vary per shop and all ref. current densities

Chris Snyder
plater - Charlotte, North Carolina

The following equation may help you: H = 0.4 * W * T * J/F

where H is layer thickness in microns
W is Anodic efficiency
T is time in minutes
J is total current (amperage) in amperes
F is surface area in sq.dm

(Anodic efficiency is around 65%)

Jan Prichystal
Audio-visual - Denmark

I would suggest using the 720 rule. Try using this formula:

Square feet x Amps / Square foot = Anodizing Amps
Example (500ft2 x 20 amps/ft2 = 10,000 Anodizing Amps)

Square feet x Mill Required
___________________________
Anodize Amps x 720 = Anodize Time

Example-
500ft2 x .70 Mills Required
___________________________
10,000 Anodize Amps x 720 = 25 minutes Anodize Time

This should get you very close depending of course on tank temp or part thickness.

Bruce Pfaff
- Wausau, WI

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