Pickling carbon steel pipe is a very caustic process. A pickling reservoir is essentially a pure acid bath that will strip everything off the steel. Any foreign matter, rust, grease, oil, everything. The pickling process is so harmful that it is not allowed in any Metro Detroit plant and pickling facilities are strictly regulated in areas where it is allowed. It is so caustic that any building housing the pickling reservoir will be literally destroyed within 30 years. Environmentally safe, our pickled carbon steel pipe comes directly from the mill.
Part of the pickling process is to coat the steel in a light oil after stripping it bare. This has to be done immediately or it will start to rust. Pickling is used very prevalently in hydraulics. No foreign materials including bits of rust or steel flakes can be present as they would not be filtered through a hydraulic pump for example.
For stainless steel it is referred to as Pickle and Passivation. Pickling is done first, where again any foreign particles are removed and the stainless steel surface is metallically cleaned (purified). Passivated where a dense passive layer can form only on a pure surface from the chromium oxide. This ensures corrosion resistance to other elements in stainless steel. Pickling Passivation is also done in an environmentally safe facility and shipped directly to us from the steel mill.