"NO! Cast is one thing. Steel black pipe is something totally different.It would cause oxidation. Then a leak,then a big boom"
Where do people get these ideas?
Cast Iron pipe was used for over 100 years as gas mains in many older cities. The old reason cast fittings are contrary to code is the possibility of a sand hole during casting or the fitting cracking because someone made it up to tight
The reason galvanized fittings were not allowed to be used in doors was the zinc coating may have covered a defect in manufacture.. Before taking any advice off any list make sure the advice giver has some kind of formal education