Anodized Aluminum in High Pessure/Temperature

[SteveCon]

We are considering using hard anodized aluminum components for an in-mold (platic molding, rubber molding, etc.) sensor. We need the electrical insulating properties of the hard anodized coat. We are planning to use a 7075 aluminum alloy. Does anyone have experience using hard anodized aluminum in the following or similar application:

1. Shrink or press fitting hard anodized aluminum components together. Is this possible and how difficult is it?
2. Exposing the hard anodized surface to high temperatures (300F to 450F) and pressures (10,000psi to 30,000 psi). Does the hard anodized layer chip off or survive in these types of environments?
3. Cyclical compression loads. Does the hard anodized layer improve or reduce aluminum's fatigue resistance?

Any experiences with situations even remotely similar to these would be very helpful.

 

[TVP]

There are a number of good sources of information related to anodic coatings on aluminum alloys, and this topic has been frequently discussed among the Eng-Tips forums. I recommend you perform a search of this site and review the previous threads.

I don't want to comment too specifically on your questions, but remember that the anodic coating is a hard, brittle ceramic layer, and therefore is quite susceptible problems with thermal cycling, fatigue, etc. I can tell you for sure that fatigue performance of aluminum is reduced after anodizing, and repetitive thermal cycling will exacerbate the problem. Compression loading is more favorable, but can still generate tensile stresses somewhere in the coating, so this is no guarantee for favorable performance.