Effect of nano yttria stabilized zirconia on corrosion behaviour of chromium oxide coatings on boiler steel

In this research work, 5 wt.% nano yttria-stabilized zirconia (YSZ) reinforced chromium oxide-based nanocomposite coatings were prepared and successfully deposited on ASME-SA213-T-22 (T22) boiler tube steel substrates using high-velocity oxyfuel (HVOF) thermal spraying method. The corrosion behaviour of composite coating has been compared with that of conventional chromium oxide coating. All the coatings were analysed by scanning electron microscope, energy-dispersive X-ray spectroscopy and X-ray diffraction. It was found that the addition of 5 wt.% YSZ in the Cr2O3 matrix results in the reduction of the porosity of the coating and an increase in hardness. During corrosion investigations, it was found that YSZ-reinforced Cr2O3 nanocomposite coating on T22 provides better corrosion resistance than conventional Cr2O3 coating in the molten salt environment at 900 °C. The inclusion of YSZ has reduced porosity by filling in the gaps in the chromium oxide coating, causing particle interlocking, and preventing the entry of corroding species.