Hi everyone!
My first post here! I’m so excited to be a part of this community. I watched a video of etching with salt and copper sulfate on cold-rolled steel. However, I ended up with mild hot-rolled steel by mistake. How much of a difference would this make when etching with the copper sulfate/salt combo? Would Ferric Chloride work better? I have no experience with steel (as you can tell). Any other ideas? Thank you!
It will make no difference to the etching.
It would make a difference if you’re planning on cold-working the steel and a tiny bit of difference on a lathe or a mill, but the acid will bite either just as well. Just make sure to start with a uniform, cleanly sanded surface.
Thanks Elliot. Someone told me that the coating was the problem and to either sand it off or put it in vinegar over night…so I guess I’ll try that too. Thanks! 
Cold rolled has no scale. Hot rolled has scale. The easiest way to remove the scale on hot rolled is by letting it sit in a dilute muriatic acid solution for about 15 minutes. Sanding will take you forever and be really messy. After the muriatic acid bath rinse it well. You can get muriatic acid in the pool section of any home improvement store. Read the cautions. You can use baking soda to neutralize the acid.
I’ve sanded the mill scale off before and can say that if there is any other way to do it then you should give that a go. The scale is a bit harder than the steel so it takes ages to get rid of.
I placed them in vinegar overnight and the coating came right off!