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montanaman
March 18th, 2017, 19:59
Hi guys ... I don't know much about painting, so I thought I'd ask NAXJA:

New steel usually comes with a gray coating, which I guess is there to prevent rust. Not sure what it is, but should it be painted? Or should I strip it off before painting?

If it needs to be stripped, how do you do it? Chemicals, flapper wheel, or some other method?

Thanks.

xCWolf
March 18th, 2017, 20:09
As far as I understand you can use aircraft paint thinner/stripper to get it off

Tim_MN
March 19th, 2017, 07:04
What kind of steel, and for what kind of project ? Cold rolled steel, which includes sheet metal, should only need solvent cleaning and scuffing before primer. Hot rolled steel tube or steel plate will give the best results if the mill scale is ground or sandblasted off. Solvents will have no effect upon mill scale.

montanaman
March 19th, 2017, 10:07
Thanks for the replies. Yeah, the magic words were "mill scale." I didn't know it was called that. Its the dark gray stuff on plates of mild steel. It's just ordinary steel that I bought from the local steel provider (Pacific Steel). I bought it for various projects, but right now I'm making a little mounting plate for an in-line fuse for my alternator upgrade. Tons of videos on YouTube for removing it with hydrochloric (muriatic) acid, sand-blasting, etc.

Thanks!