The controlled chemical removal of surface oxides (scale) from iron and steels by immersion in an aqueous acid solution. The most common pickling solutions are carbon steels sulfuric and hydrochloric acid solutions and nitric and hydrofluoric acid solutions for stainless steels and titanium alloys.

Pickle and etching is limited to oxide removal and seldom exceeds material removal greater than 0.001” per surface. Removal of 0.0001” to 0.0002” is usually sufficient to remove oxides.

Hydrogen embrittlement relief bakes may be required for high strength steels heat treated to HRC 39 and greater.