The Impact of Iron(III) Chloride (and Iron(II) Chloride) Content in Hydrochloric Acid Pickling Solution on the Pickling Process

It is known that when hydrochloric acid solution is used for pickling steel pipes, industrial hydrochloric acid is directly employed for this purpose, which allows for a faster pickling rate. During the pickling process, the steel pipe's iron matrix reacts with hydrochloric acid to produce iron(III) chloride and iron(II) chloride. Iron(III) chloride acts as a corrosive agent, accelerating the pickling process. Therefore, to achieve a higher pickling rate, a certain amount of used hydrochloric acid can be added to a fresh hydrochloric acid solution.