Originally Posted by
Banzai
The other potential issue is the version that comes in the anodized finish. Anodization is a big no-no in aviation. The problem is that the alumina layer on the surface, which is literally a part of the substrate metal - grown into it, if you will - is far harder and far more brittle than the substrate. When it cracks...which anodized finishes often will do under strain, it's not like paint cracking. The crack in the finish propagates to the softer substrate, and results in component structural failure.
Not to disagree, but 4 years of working in the aviation hydraulics industry disprove this. On hydraulic and pneumatic components, anodization is a requirement on both 7075 and 6061 components. Hard anodize is frequently used on pistons and actuator bodies. Even painted aluminum components are anodized under the paint, at least on the components and actuators I dealt with. So to say anodize makes components fail for crack propogation seems... well, inconsistent with my experience.