I’m not sure if there are some metals it attacks, but in general it’s a solvent for plastics and other organic compounds, it’s not an acid that etches things. Acetone is commonly used to clean oil from metal parts prior to painting and does not affect the metal in any way (at least for metals that I am aware of).
There are several commercially available acids that can be used to etch steel and stainless steel, including hydrochloric acid, nitric acid, or sulfuric acid.
Nitric Acid – Works well on most metals. Mix it with water at a ratio of 1 part acid to 3 parts water. Or it can be mixed with acetic acid (vinegar) in a 1:1 ratio. Sulfuric Acid – Works well on most metals.
Ferrous Chloride can be used to etch copper or zinc plates, while nitric acid can be used to etch zinc or steel plates. Typical solutions are 1 part FeCl3 to 1 part water and 1 part nitric acid to 3 parts water. The strength of the acid determines the speed of the etching process.
There are some acids that will etch stainless steel, including hydrochloric, nitric or sulfuric. But the ferric chloride is a stronger acid, so it works faster.
Muriatic acid is “hydrochloric acid” (HCl) in a less pure and diluted strength for non-technical applications such as cleaning bricks. Ferric chloride is an iron “salt” of HCl that is still very acidic, although not as “strong” as HCl. Both will eventually etch any high carbon steel.
Mix baking soda with distilled water and use a generous amount of baking soda to dip your piece to neutralize the acid and stop its dissolving effects.
Caustic acids can range from strong hydrochloric or sulfuric acids to much weaker acids – even household vinegar, citrus fruit or mustard can be used effectively. In the video linked above, YouTuber TheSmokinApe etches an ESEE blade with French’s mustard.
Phosphoric acid has been used extensively in various concentrations as an etchant to improve the bonding of dental materials to enamel surfaces. Recently, attention has been drawn to the potential use of polyfunctional organic acids as conditioning agents.
You should probably use sodium hydroxide and not acid to etch aluminum. Also known as caustic soda, this material has the chemical formula NaOH. The most accessible form is probably Drano [affil.
The parts are then oiled and left overnight. This process leaves a deep blue-black finish. Modern, do-it-yourself versions of this process typically use a solution of hydrogen peroxide and salt, sometimes with vinegar, for the rusting step to avoid the need for more dangerous acids