Anodized Rotor Housings
 

I am weighing out the different options for rotor housing finishes and was curious why I don't see anodized housings.

How would you reliably mask off the chrome? Not entirely sure if the costing will even stick to that area but why risk it? Anodizing can be very expensive and outside of the cosmetics, the corrosion protection it offers isn't all that beneficial, if at all. Whatever choice of paint people prefer has been fine for looks and corrosion prevention for the past forever. Give it a try though, get a junk housing and anodize it. See what happens.

If you talk to an anodizing place they are unwilling to anodize most cast aluminum items like wheels where the reason for anodizing is aesthetics.

You get a lot of uneven looking coloring I guess- they would prefer brand new billet or forged aluminum parts.

I was told you will get the best results with hard anodizing process (available in fewer colors).

The way the anodizing process works is by first dipping the part in a acid bath to remove the oxidation on the aluminum surface, and then the anodizing is actually a chemically controlled build up of "rust"

For the most common type of anodizing, type II, is a zero loss or gain process so whatever the acid removes, they plate the same thickness back on. This is why its so common, people think the part stays the same size, and manufacturers don't have to compensate the machined part for the plating thickness. The downside being, your part is being eat away, you just don't realize it when there's a shinny new case on it.

I'm guessing the reason people don't anodize housings, beyond cosmetics, is that even if you could mask off the chromed surfaces well enough, you'd still loose sharp corners on stuff like your coolant seal grooves, and internal webbing may be eaten away because it has so much more surface area exposed to the acid. It could also affect how the chromed sheet metal piece is held in place. These are all tiny numbers, less than .002", but those are also the tolerance or a big chunk of the tolerances, you have when assembling a motor.

You'd also be anodizing the water jackets. Which would be bad. The last thing I'd think you'd want in the cooling system is a layer of insulation.

AGREE 100%! Not a good thing for the cooling passages, but they could be masked / prevented from accepting the anodizing (with a lot of effort).

What about ceramic coatings? I did ceramic coating on the piston tops, combustion chamer, and valves of a hot LS1 and has excellent results. Has anyone tried this on a rotary?

Ceramic coating is not a good idea for the external part of the engine. It keeps too much heat from getting out. Coating the rotors can be good so they don't get heat soaked. I say paint or nothing.

Thanks to all that replied. In regards to paint, what should the temperature of the paint be rated at?

I've used the high temp and the high-er temp stuff and got the same results. The more important thing is the prep but anything that says high temp will be fine.

There are two types of ceramic coatings. When most people think it, they rightfully think of it as a barrier or blocker of heat since that has been the case for decades. Over the last several years the coating industry has developed dispersant type ceramic coatings, which actually promote heat transfer. They are supposed to have small particles in the coating that increase the surface area and therefore help the transfer of the heat to the air. I have used both types of these coatings on my recent rebuild. In example, I used barrier on the underside of the UIM and dispersant on the top. Block the heat from the engine and blow off the heat from the metal under the hood. I used barrier along the inside of the runners.

I believe a dispersant coating on the outside of the block could be beneficial since it would help cool the block along with the cooling and oiling system, particularly in a high boosted beaten on tracked car.

Mike