How to etch steel

I am an artist looking to use an acid to etch my work into thick steel up to four inches thick. Can a normal person be able to get such a chemical? What would work the fastest? What would be the safest?

ferric chloride ⇦ on eBay or Amazon [affil link] is one of the "safest" chemicals and very effective for etching steel. Anyone can easily purchase it but you didn't mention how deep you want to etch (hopefully not through the full four inches thick). It etches better when slightly warm and agitated (about 0.001" in 5 minutes). What are you going to use as maskant? You should search for "etching procedures" in your favorite search engine.

dear sir

I do brass etching. I am wanting to do steel etching also.
but I do not know what acid to use.
the sheet is about 1.2 mm.
please will anyone tell me how to do this.

thank you.

Go to your local library and get a copy of "Step-by-Step Knifemaking" by David Boye,published 1977.
Chapter 19; page 211/ "Etching Designs into Steel" it covers everything and every facet..from making the etching resist to multilayer etching, and it has the formula for Aqua Regia [the only known acid that will dissolve gold ]