believe me, I know well the properties of mill scale, and have come up with a few tricks to bust up the stuff, with minimal tools, equipment, and time, but still find those pads and an angle grinder to be readily available and highly cost effective.
aluminum oxide "sandpaper" is NOT my first choice, for the simple reason that one of the constituents of some mill scale IS aluminum oxide. (ever wonder why some scale is nearly impervious to a regular sanding disk?)
thus my go to is a disk with corse silicon carbide grit.
if it is a relatively small piece for a good paying client, I am having a hard time thinking why cold rolled would not be the starting material, even if it were to be "machined for appearance" ?
and also, a machined surface, preformed pre-weld on a weldment, (which is going to distort from the welding anyway) where not specified, just looks dumb and un-professional in my book.
more "what the hell were they thinking" than "nice job" to me.
not trying to be mean, hope you get it that I'm just latin' it out there the way its gonna come off to a pro..I think. anyone else that would have the same thought?