Black iron pipe comes coated in oil, presumably to prevent rust but possibly as a side-effect of having been machined. Does that oil need to be removed from the threads before assembly with thread compound?
My concern is that any contaminant will affect the thread compound bond.
Best Answer
My answer is yes threads need to be clean. However it probably depends on what is used for sealing. Black pipe is normally used for gas. I don’t want any leaks and pipe dope both gas rated and regular state the threads need to be clean and dry. I don’t remember ever seeing info on white or yellow tape but I have wiped the threads as I use oil when threading so it has become a practice to wipe fittings for gas if I thread them or not and with either tape or dope.