Effect Of Chlorine Ion Concentration On The Pickling Process For The Oxide Scale Of Hot-rolled Ferritic Stainless Steel

Stainless steels are used extensively in many fields such as building and manufacturing etc. for their good mechanical properties and high corrosion resistance. However, it is easy to produce continuous, compact and adherent complex oxide scale structure on the surface of stainless steel due to high-temperature oxidation during hot-rolling processing. The residual oxide scale will be pressed into the surface, which not only affects the appearance quality and properties of parts but also influences the subsequent processes of stainless steel and accelerates the corrosion of stainless steel.This paper researched compositions and structures of the oxide scale of hot-rolled430and443ferritic stainless steels on the pickling process by the different concentrations of Cl-. Metallographic microscope, scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and glow discharge spectrum (GDS) were employed to analyze these characteristics. Moreover, the compositions and structures of passive film formed on the surface of the hot-rolled430and443ferritic stainless steels were analyzed in order to find out compositions of passive film.Effect of concentrations of Cl-on the pickling process for the oxide scale of hot-rolled430ferritic stainless steel was analyzed. The results indicated that the concentrations of Cl-in pickling agent significantly impact the removal of oxide scale. When the concentration of Cl-is Cmg/l, the oxide scale which is strongly adherent to the underlying metal can be more fully removed. The concentrations of Cl-also influence the quality of the passive film. A dense and corrosion resistant passive film on the hot-rolled430stainless steel can be generated by pickling process with above-mentioned concentration of Cl-.The compositions and structures of the oxide scale of hot-rolled430and443ferritic stainless steels on the pickling process were analyzed. The results showed that there is trace amounts of discontinuous residual oxide in the443stainless steel matrix and oxide interface which mainly is Cr oxides when the concentration of Cl-is Cmg/1. It was turned out that the oxide sclale of the hot-rolled443stainless steel which is strongly adherent to the underlying metal is more difficult removed than the oxide scale of the430stainless steel. A dense and corrosion resistant passive film which is Cr oxides on the430stainless steel can be generated by pickling process with above-mentioned concentration of Cl-.