Electrophoretic coating (e-coat) is a cool process. The bath is charge 100-300 volts. The aluminum is a cathode causing the coating to deposit on the surface. As the coating becomes electrically insulating the deposit process natural slows.
I was looking into it as an alternative to anodization that's rather nasty for the environment but then became intrigued by sol-gel that seems to have the properties we're going for with much easier factory processes.
Have you ever seen a car painted?
I found it interesting. It looks like a second coat of primer.