Anodizing and coloring for aluminium

I'm facing a color tone variation in coloring process for aluminium. Can somebody tell me the timing for coloring process? Is there any formula for the coloring process? As I know the coloring process depends on the surface area, products' profile. Is there any standard operating procedures (S.O.P) for the coloring process for aluminium after anodizing? thanks, hope someone can help.

Hi, Jay. Is the anodizing and coloring done in-house or by a vendor? In either case you need to visit the place where the process is done, and get a better understanding of it. You probably do not yet know enough about the process to be able to address this problem that you have been assigned. After you have seen it you will be able to consider such things as the alloy being anodized, the thickness of the anodizing layer, whether the color comes from organic dyes, or a "two-step" or integral color anodizing process, etc. Robert Probert's "Aluminum How To" is an easy to understand introduction to anodizing of aluminum. Good luck.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

Jay

Presuming the dye process is with organic dyes...

Variables that will effect the final color include:

alloy, acid concentration, aluminum content, solution temperature, load size, current density, amp-hour/sq.ft., coating thickness, dye strength, dye pH, dye temperature, dye dwell time, seal parameters.

Some color variation is to be expected, but control the variation on those parameters that are most like to shift from batch to batch.