Effects of Different Oxidants on HCl-based Pickling Process of 430 Stainless Steel

Abstract

To shorten the time required for the pickling process and to enhance the quality of ferritic stainless steel plates, the effects of oxidants including hydrogen peroxide (H₂O₂), potassium permanganate (KMnO₄), and potassium chlorate (KClO₃) on the pickling behavior in HCl-based electrolyte as well as the surface quality of hot-rolled and blasted 430 stainless steel (430-SS) were studied. Experiments were conducted using mass-loss tests, micro-structure analyses, potentiodynamic polarization curves, and electrochemical impedance spectroscopy measurements. The results showed that the addition of oxidants substantially accelerated the pickling process of 430-SS by enhancing the cathodic reaction rate and reducing the charge transfer resistance. In electrolytes comprising 5 – 8 mass% HCl at a temperature of 40 – 60 °C and at the same concentration within the range from 0 to 2 mass%, H₂O₂ was demonstrated to be superior to KMnO₄ and KClO₃ in accelerating the pickling process. The surface quality of 430-SS pickled in the presence of H₂O2 was better than those of specimens pickled in the presence of KMnO₄ and KClO₃ when the removal of the oxide layer, intergranular corrosion, and surface roughness were collectively considered. When 1 mass% H₂O₂ was added, the mass loss rate of 430-SS was increased by 629% and no residual oxide layer or intergranular corrosion was observed on the surface of the steel; in addition, the roughness was only 1. 7 µm. H₂O₂ was determined to be a better oxidant than KMnO₄ and KClO₃ when the pickling process, surface quality, solution recycling, and environment protection were considered as a whole.