Except the steel in question is an austenitic stainless so the oxide layer would contain nickel and chromium oxides.wim said:In simple terms, "anodizing" means increasing the natural oxidation layer of a metal. If you would anodize steel, you would increase the natural oxidation layer of steel, which is rust. No go.
As it happens you can anodise stainless steel and the oxide layer is black in colour due to the chromium oxides. I do not believe that this is the process the spoke makers use, however, as the surface layer on anodised stainless is notoriously easily damaged.
BTW anodise comes from "anode" from the Greek "anodos" meaning "uphill" (so named because it is the electrode at the higher potential, the opposite one is the cathode from "cathodos" meaning "dowhill".