Annodized metals & heat?

[Matt Park]

how well does it resist heat? what parts, for example could you NOT anodize?

[Mike Schmid]

If you can get BOVs, AFPRs, ignitions, et al anodized it'll take any heat in the engine bay unless you want to make your pistons black or something.  Who knows, it might even stand up to that if you had the urge to try.

[Martin Raska]

Heat sinks for electronics are typically anodized, and they can get pretty hot.  We've used a anodized aluminum crank position sensor cover with no issues which probably gets as hot as most of the things you'd want to colour anyways.  You probably wouldn't want to anodize pistons or high stress components due to the stress concentrations (albiet they should e minor) it creates, but there are other ways to make pistons black if that is your desire.

[Ritchie Hui]

if you have a cheaply made anything... annodizing might weaken it tho right?

[Kimyee Lai]

Not unless it's only a few thou thick.  Anodizing takes away some of the parent metal, but we're talking a maximum of 2 THOUSANTH of an inch.  IF the coating is cracked, the cracks MIGHT act as stress risers on a parts that sees severe fatigue loads.

As far as temperature resistance goes, the only issue is that Al2O3's coefficient of expansion is ~1/5 of pure Al.  This means if it gets too hot, or repeated heat cycling could cause the coating to crack.  I do notice my IC end tanks look a little crazed, but it's only noticeable when viewed closely at certain view angles.  You typically wouldn't want to go much more than 300C, and even then it'd have to be coated with that in mind.