I was told I should beware of arc welding zinc coated metals because of the noxious gases caused by the zinc coating. Don't know how true that is, but makes me wonder - Can ordinary black iron pipe (like the stuff you find in the piping section of Home Depot) be arc welded to regular mild steel?

Angle iron, mild steel, and black iron - for all intents and purposes, is this stuff the same when it comes to arc welding? Or are they all trade names for mild steel?