So, I keep going back to this anodizing well, for some reason. I can’t quite pinpoint why, exactly, but the whole “electricity and special sauce makes metal better” thing is fascinating to me. And, if electricity and special sauce weren’t enough, it turns out there are multiple variations of the anodizing process.
Regular anodizing uses chromic acid. At least, I’m going to assume it’s considered “regular anodizing,” because it’s referred to as Type I, and I can’t imagine why you’d call anything that wasn’t essentially the default setting “Type I.” I don’t really know what chromic acid does, but I’m going to guess that it’s probably the dangerous kind of acid that could actually melt your face off, rather than the fun kind of acid that only makes it seem like your face is melting off.
Bump that deadly danger juice up a few notches to sulfuric acid, and you’ve got yourself Type II and Type III anodizing. From what I can tell, Types II and III result in thicker coatings than Type I. Type III is commonly called “hardcoat anodizing,” which leads me to believe that the resulting coating is harder than what you get with other Types. (I’d look it up to find out for sure, but Google is all the way over there.)
One can also replace the chromic or sulfuric acids with other acid flavors, including phosphoric acid and organic acids. If organic acids are anything like the organic vegetables at the green grocer’s, they’re really just the same thing as the non-organic kind, but with more dirt on them. Also, processes using these other types of acid don’t get their own number, so there’s no Type IV or Type V or Type XXXVIII or whatever. Somebody really dropped the ball on that one, like when Mission: Impossible IV lost the numbering and was called Ghost Protocol instead. Dumb.