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topic 7950

Non-Stable Black Color


(2001)

Has anyone experienced a situation where their black anodized aluminum parts have changed color to a reddish/pink? I have had several parts from 2 anodizing vendors do this. The parts are certified to having been anodized to Mil-A-8625 [link is to free spec at Defense Logistics Agency, dla.mil], Type III, Class 2, Black.

Anthony Shafer
- Anaheim, California, USA


First of two simultaneous responses-- (2001)

Yes, the Mil Spec Type III black does not get sealed, as does Type II, giving you the best abrasion resistant surface but lowering the resistance to color fading. If the part's purpose is more of a cosmetic nature and will allow for a loss of abrasion resistance, then you must specify a "seal" on your purchase orders.

Good Luck

Bill Grayson
- Santa Cruz, California, USA


Second of two simultaneous responses-- (2001)

Sir,

There are many black dyes out there for us anodizers to purchase. They each have different lightfast & heat-fast ratings. Some would fade with outdoor use & or too much heat exposure. That could be your problem.

The other possibility is that the parts were not properly sealed. Even if the anodizer used the best dye available, a poor seal would allow the color to leak out. You can test the seal.

David A. Kraft
- Long Island City, New York



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