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Black anodizing changes to yellow

hello
I am a metallurgical engineer and work about anodizing.my specimens is aluminium.and the color of my anodizing is black.but after storing the specimens in the store the specimens's color is change to yellow or gold. this problem is happening for the specimens on the top of container in the store.

Amir Khakzad
mottahed - Tehran, Iran
2006

Your anodize color is fading either because the black dye is not reasonably lightfast or because of inadequate sealing. The fact that the parts exposed to the most light fade dramatically, makes my first guess a problem with the dye. There should be no silver in the dye, and it should be a good grade made for the purpose.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Need quick confidential answers? $25
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2006

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