How to clean hot rolled steel for preparation of a rust finish?

What can be used to clean hot rolled sheet steel to remove the factory coating? The reason I ask is because I make lamp shades and finish them with a rust finish. Someone had suggested I use muriatic acid? Is there a less toxic chemical available to clean this rolled sheet metal with?

Dear Philip

You don't obligate to use Muriatic Acid , as a matter of fact every acid will do the job including citric acid ⇦ on eBay or Amazon [affil link] . You have to remove the natural oxide layer which existing on the metal surface and then you will get rusted again.

TIP - You can increase the rate of rusting by using Salt Spray cabinet . Just put the part in it and you will get every level of rust you want

I assume that you need to remove the scale from the steel. Inhibited phosphoric acid at 50-70 deg C preferably containing degreasing additives (commercial products readily available)will do the job in a stainless steel tank. Water wash and use a final hot rinse containing rust inhibitor. If you require higher paint performance you may need to consider further pretreatment stages.

To remove any deposits of white rust I suggest an ambient temperature immersion in inhibited phosphoric acid with HF based activator. Immersion time 5 - 10 minutes then rinse in cold water and dry.