Protective coating or scale? on cold roll sheet

[rollernose]

I am trying to put a bright finish,without without heavy grind marks, on 14ga. cold roll steel.
I have had good results with material that has been left out and has some mild rust. The new sheet I have purchased has a blackish blue coating that is very difficult to grind through and still leave a smooth finish. Is there a way to cut that layer without grinding?

Thank You

 

[MikeMilburn]

I would suspect the coating you're talking about is mill scale, it's as hard as h**l to grind and get a smooth even finish.Any consideration given to a mild snadblasting for the end finish you want, if not, a weak acid solution to remove the scale. Hopefully someone with more experience will step in here...Mike