@Magaro is right.
Hardcoat anodizing (Type III) is actually used as an insulator. Its dielectric strength, how much voltage it can resist, is above 1,000V/mil of thickness. A typical hardcoat is about 0.5mil thick with about 0.5mil penetration so that makes it a great insulator. And it is
hard! Really chews up drill bits. I use it as the insulator between MOSFETs and heat sinks in some of the stuff I design. It's an incredible heat conductor though, versus other electrical insulators, because it's so thin.
Regular anodizing is much thinner and while it provides some electrical insulation you can't depend on it for that.