finish type for aluminum parts subject to temperature cycling

[hyperdyne]

We are producing a lighting instrument out of machined and bent aluminum. We had the prototype hard anodized. Recently we were made aware of some of the issues regarding differential in coefficient of thermal expansion between aluminum oxide and aluminum.

The light, when on, might get as hot as 90 C. And of course when off it will return to room temperature. So it will experience considerable thermal cycling.

I'm wondering if we should expect any significant problems with cracking of the coating and possibly structural weakening of the parts due to the continual thermal cycling. This is a product that is intended to last for years of use.

Also, I wonder if anyone could suggest affordable alternatives to anodizing that would provide for a finish visually similar to hard anodizing in black. I thought about nickel plating, but not sure whether it is significantly more expensive or would provide any additional benefit.

[Geof]

Many years ago it was possible to get aluminum cooking pots that were anodized and dyed bright colors. These never showed any problems during years of use.

Nickel plating is going to be much more expensive and my expectation is that it would be less resistant to thermal cycling than anodizing. Remember all aluminum has an oxidized surface and anodizing simply makes it thicker. Nickel plating is on top of the natural anodized surface at it does not adhere particularly well.