Can steel products be hardcoated?

Unfortunately, no. The only metals that can be anodized are aluminum, magnesium, and titanium. The aluminum oxide is created by electrochemically converting the base aluminum to aluminum oxide. All other metals will dissolve and plate out onto the cathodes.

What alloys are preferred for anodizing?

Higher purity alloys are always preferred for anodizing. Alloying elements such as copper and silicon do not anodize and leave microscopic voids in the aluminum oxide film. Since the anodizing process converts only the aluminum to aluminum oxide to form the anodized...