Corrosion Behavior of Plasma-Sprayed Cr2O3 and Cr2O3-20YSZ Coatings in13.5wt%NaCl Solution with and Without Sealing

In the present work, Cr2O3 (C) and Cr2O3-YSZ (CZ) coating were produced using ball milling of the starting powders, mixing the milled powder, and subsequently atmospheric plasma spraying of the agglomerated powders on 304L steel substrate. The corrosion behavior of the coatings with and without sealing was evaluated by electrochemical potentiodynamic polarization and electrochemical impedance spectroscopy as well as immersion tests in a 3.5% NaCl solution. The results of microscopic image analysis showed that addition of YSZ to C coating caused an increase in coating porosity from 8.7% to 10.2% and a decrease in splats degree of flattening. Data obtained from electrochemical tests indicated the better corrosion resistance for individual Cr2O3 coating that was related to its denser microstructure. Sealing treatment by limiting electrolyte access to the substrate surface considerably increased the corrosion resistance (ohm.cm2) of the C and CZ coatings from 191 and 379 to 23189 and 77916, respectively.