Summary for blue anodize appearance Discussion
Blue anodize appearance is the key issue in this short thread: a customer wants 7075-T6 and 6061-T6 to look exactly the same after blue anodizing. Gene Ho asks whether that expectation is reasonable. Robert H Probert replies with a pointed answer: not really, unless the 7075 is made to have the same chemical analysis as 6061, which is not practical in normal production. The exchange implies that alloy differences can affect anodized appearance, so matching color and finish across different aluminum alloys should not be assumed to be automatic. The practical takeaway is that identical blue anodize appearance across 7075 and 6061 may be difficult or unrealistic, and any appearance requirement should be evaluated against the base alloy differences.
Q. Our customer ask to keep exactly the same appearance after 7075T6 and 6061T6 blue anodized. Is that reasonable ?
Gene Ho
– Tai-chung , Taiwan
2006
A. As long as he maintains the same chemical analysis for 7075 as 6061 :-)
Ted Mooney, P.E.
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
Need quick confidential answers? $25
Need project assistance? $100/hr.
2006
At lower thicknesses the 6061 and 7075 come out very close to the same color, however, as thickness increases the 6061 tends towards tan-black, and the 7075 tends towards blue-gray. This is because of the different alloying ingredients. You may override this tendency with higher free acid, perhaps 200 gm/L, higher temperature up to about 75 F, and lower current density, all three parameters make a larger pore and would adsorb more blue dye and bring the two alloys closer together.
Robert H Probert
Robert H Probert Technical Services
Garner, North Carolina
2006
Thanks for the help everyone!
Gene Ho
– Tai-chung, Taiwan
2006