Some clarification for my comments above.
"Magnesium can be anodized but its applications are very limited. Titanium is perhaps the second most commonly anodized material, though still nowhere near as popular as aluminum. Some materials simply should not be anodized. Carbon steel will simply corrode if it is brought through an anodizing process"
"Anodizing is an electrochemical process that converts the metal surface into a decorative, durable, corrosion-resistant, anodic oxide finish. ... This aluminum oxide is not applied to the surface like paint or plating, but is fully integrated with the underlying aluminum substrate, so it cannot chip or peel.
Anodising is an electrolytic conversion coating – it transforms aluminium on the surface of components into aluminium oxide. Since aluminium converts rather than deposits, some of the thickness of the coating is ingress into the material and some of the thickness is growth out of the material. For most alloys, the anodised coating is approximately 50% ingress and 50% growth. The growth of coating from the original surface is therefore half the stated coating thickness. Internal diameters will get smaller by approximately the coating thickness and external diameters will grow."
Typical coating thickness is only .002" for a heavy application so that translates to 001" penetration and an additional .001" on the surface. For most areas this is negligible but for pin and bearing fits can cause you problems. It also makes the surface harder, and extremely thick applications are sometimes referred to as "Hardcoat Anodize"
With that said I love what WIllis is doing with his wheels, very nice contrast and look. I also like the early discs and have purchased a couple extra to use for my build.