Precision casting manufacturers detail the use of acid solutions to remove oxidation and rust from the steel surface is called pickling, which is also a way of cleaning the metal surface, generally carried out together with pre-passivation solutions. This is also a way of cleaning the metal surface and is generally carried out together with a pre-passivation solution. Generally, the product workpiece is infiltrated into a solution of, for example, hydrochloric acid to remove metal oxides and other plastic films from the metal surface, which is also a preparatory treatment or intermediate solution for electroplating processes, pond porcelain, cold rolling and other processing processes.

Passivation: If the metal material because of the effect of the substance and the occurrence of the leaching material, with a high-density structure and produce a film, generally not thus visible, will closely cover the metal surface, then the surface of the metal material will be changed, and the electrode potential of the metal material is further increased. Along the positive direction oscillation, become anti-corrosion in a passive situation. For example, when Fe → Fe2, the norm potential difference is -0.44V, after passivation jumped to 0.5 ~ 1V, indicating the precious metal characteristics of corrosion resistance, the film is called passivation film.

Passivation of metallic materials can also be a spontaneous full process, such as producing a layer of insoluble chemicals on the metal surface, i.e. an air oxide film. In industrial production, passivators are used to passivate metallic materials to produce a protective film. The primary and purpose of pickling is to remove oxide from the surface of stainless steel castings. Wax precision castings therefore do not require pickling of stainless steel castings, but only when there is oxide on the surface. For example, with the maintenance of vapour, such as pure hydrogen and ammonia dissolved quenching of stainless steel castings without pickling.

Stainless steel plate pickling is generally associated with passivation, must be pickled stainless steel castings are generally passivated, due to the cast steel parts precision castings in the pickling on the surface did not produce passivation film, or passivation film thickness is very thin, which does not have a practical effect. The passivation process needs to be added afterwards to produce and sound passivation film on the surface of the stainless steel sheet. This film is important for the stainless steel sheet to be rust-free and corrosive in general.