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Fading of Black Anodizing on heatsinks

If this occurs is there any deterioration in the heat dissipation rating of the heatsink?

By what factor does anodizing increase the heat dissipation of the heatsink, if at all?

Is there "spray" that can be used to
1. Seal existing non discolored heatsinks,
2. to repair the discoloration?

Keeping on the repair theme, can I spray a black "engine" high temp paint on the heatsink and retain is dissipation properties

Michael Melle
- Edmonton, Aberta, Canada
2005

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2005

While I've seen some debate on the subject (I think that letter 31529 contained some), all the research I've seen makes it pretty clear that heat dissipation is not affected by color, the only time you get a significant difference is in heat absorption.

Now, I have read that a thicker coating is better (Wernick, Pinner and Sheasby state that a thick hard coating is well on its way to black-body status - reaching 80% emmisivity at 10 µm and increasing from there). So, the only way your fading should pose a problem to you is if it is fading because of attack on the anodic coating itself - but that would be doubtful and you should be fine.

If you can get a hold of a copy of "The Surface Treatment and Finishing of Aluminum and Its Alloys" by Wernick, Pinner and Sheasby, it covers the subject pretty well.

Good luck,

Jim Gorsich
Compton, California, USA