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High temperature aluminium blackening process

I am trying to find a process that will allow me to blacken aluminium, and can withstand a continuous operating temperature of approximately 250 degrees C. The component I am currently developing has some fine threads, thus painting or powder coating are not exactly suitable. The component is visible so I am looking to maintain a relatively neat finish. We have tried Anodising black however the continuous temperature tends to turn the finish purple or bronze/gold. I have made some inquiries regarding chemically etching processes but no-one seems to be able to guarantee any consistency with aluminium.

Glenn Lynch
- Brisbane, Queensland, Australia
2002

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2002

If your parts are fading at these low temperatures your anodizing source is either NOT SEALING the parts, for example nickel acetate seal, or using a cheap black dye with poor HEAT FASTNESS. It is a standard test for black anodized connector shells to be heated up to 500F+ for 60 minutes without degradation. I might suggest that you contact Clariant and inquire about Deep Black H3LW dye or Deep Black MLW. We've used both with success in similar applications. If this conventional black anodize approach still fails, electrolytically converted anodic films offer blacks that withstand the rigors of sterilization for the medical industry and space for satellite use. Good luck down under from up over!

Milt Stevenson, Jr.
Syracuse, New York