Effects of Al and Ni doping on oxidation and corrosion resistance of electrophoretic deposited YSZ coatings

Yttria-stablized zirconia (YSZ)/(Ni,Al) coatings were deposited on Inconel 600 alloy substrate by the electrophoretic deposition combined with vacuum sintering technique. The effects of isothermal oxidation at 1100 °C on the composition of the coatings and the crack healing were investigated, and the corrosion resistance of the coatings in 3.5% NaCl (mass fraction) solution was also studied. The results showed that the cracks on the coating gradually healed up with the increase of the isothermal oxidation time. During isothermal oxidation process, the coating composed of Ni3Al was transformed to α-Al2O3 particulates. The α-Al2O3 particulates can seal the defects such as pores and cracks, and meanwhile prevent the oxygen diffusion into the coatings. The polarization curves and EIS results indicated that the coatings oxidized for 40 h had a more positive corrosion potential, higher breakdown potential, higher impedance module at low frequency and much lower corrosion current density compared with YSZ coated and uncoated Inconel 600 alloys.