The anodizing is a surface treatment that can be up to .010” thick and very hard depending on the application. It is a hard surface compared to raw alloy. It would definitely keep the wheel from being scratched or dinged easily but also corrosion. As Mark pointed out, that is until the coating wears out. If spec’s as a “hard anodize” it can be quite resilient. The early to mid Trek’s came with the hard anodized Matrix wheels that were almost black and , to me , seemed to have thicker coating. But, in time, the brake wear become visible and some don’t like the effect . I doesn’t bother me any more than the patina that comes with a bike that gets ridden a lot.