Corrosion Behaviors’ Investigation of Carbide Coatings Developed for Sulphuric Acid Recovery Systems

Abstract

In this study, corrosion resistance of cobalt and nickel reinforced tungsten carbide coatings applied to low carbon stainless steel material surfaces to reduce corrosion-induced losses in sulphuric acid recovery systems were investi-gated. During the recovery of sulphuric acid, aggressive sulphur systems in the baths cause the metal surface to dissolve and therefore a high amount of material loss occurs. In order to minimize corrosion induced material loss, 316 L stainless steel surfaces were coated with an interlayer of 95% nickel and 5% aluminium alloy, and then tungsten carbide coatings were synthesized on the surfaces of substrate materials reinforced with 13% cobalt and 13% nickel, respectively by thermal spraying method to further reduce the corrosion rate. Characterization of the produced coatings were carried out by X-ray diffraction (XRD), scanning electron microscope (SEM), optical microscope, image analyser, and surface roughness device. The standard potentiodynamic polarization character-istics of the coatings for 1M H2SO4 solution at room temperature were investigated with a potentiostat/galvanostat device. As the obtained results, nickel reinforced tungsten carbide coatings with nickel aluminium interlayer showed the highest corrosion resistance against sulfuric acid environment. With the data from this study, it was possible to observe the effects on the corrosion behaviour of HVOF carbide coatings.