Anodizing steel or stainless steel nuts and bolts

Can steel and/or stainless steel nuts and bolts be anodized?

Steel and stainless steel can't be anodized; the process baths used to anodize aluminum would attack and dissolve steel parts.

It depends on what you call anodizing. I tend to refer to anodizing as "controlled corrosion", so in that sense, steel can be anodized (we refer to it as rust) and so can stainless. However, as admin eludes to, steel in the aluminum anodizing bath is big a no-no if it has current flowing through it.

I'm sure there is process that can oxide stainless and a process for rusting iron, but neither are very common.

The closest thing would be black oxide.