Corrosion Resistance of APS- and HVOF-Sprayed Coatings in the Al_2O_3-TiO_2 System

摘要

In this article, the results of corrosion investigations performed on thermally sprayed ceramic coatings with different compositions in the Al_2O_3-TiO_2 system (Al_2O_3, Al_2O_3-3%TiO_2, Al_2O_3-40%TiO_2, and TiO_x) are presented. The coatings were deposited on corrosion-resistant steel substrates using atmospheric plasma spraying (APS) and high-velocity oxy-fuel (HVOF) spraying processes and characterized by means of optical microscopy, scanning electron microscopy (SEM), and x-ray diffraction (XRD). The corrosion properties were investigated in 1 N solutions of NaOH and H_2SO_4, at room temperature, 60°C, and 85°C, as well as in hydrothermal conditions with deionized water at 100°C and 200°C. The corrosion stability of the coatings depended on coating characteristics (spraying method, micro-structure, and crystalline phase composition) and the corrosive environment (media, test temperature, and duration). In contrast to expectations, APS-sprayed coatings were found to be more corrosion-resistant than the HVOF-sprayed coatings. Addition of TiO_2 to Al_2O_3 increased the corrosion stability, especially for the HVOF-sprayed coatings. In this work, TiO_x coatings were found to be more corrosion-resistant than the Al_2O_3-based coatings.