Zirconia coatings corrosion resistance

Several recent reports describe using clay or other inorganic fillers to form CP composites. Polyani-line-polypyrrole composite coatings containing clay or yttria stabilized zirconia were electrodeposited onto AA 2024-T3 [158], with improved corrosion resistance of the substrate. Similarly, particulate-filled polyaniline and polypyrrole films on AA 2024-T3 were prepared electrochemically using a variety of fillers, including clay, carbon black, short carbon fiber, zirconia, and silica [159]. Again, enhanced corrosion performance for these composites was observed. 

Aruna et al. (2009) showed enhanced performance of wear and corrosion characteristics of Ni based composite coatings by embedding with alumina yttria dop>ed cubic zirconia (AZY, (l-x)Al2Q3-8 mol% yttria stabilized xZxCh x = 10 wt%)) particles. The higher Warburg resistance of Ni - AZY and enhanced corrosion resistance was attributed to possible difference in mass transport phenomena in the Ni -AZY composites compared to the pure Ni with increased resistance of Ni grain boundaries in presence of AZY particles and thereby hindered the diffusion of chloride ions (Aruna et al., 2009). 

To avoid classical corrosion mechanisms, ceramics and composite materials have also been tested (some of these materials are also common components in heterogeneous catalysts). An alumina reactor for SCWO was proposed among ceramic materials only a few aluminas and zirconias did not corrode severely, whereas SiC or BN lost up to 90% by weight under SCWO conditions in the presence of HCl. The combination of steel and ceramic coatings should theoretically provide high-pressure stability and improved corrosion resistance, but only slight improvements were reported for stainless steel SS316 coated with sol-gel-prepared Ti, Zr or Hf oxides, stainless steel SUS-304 with TiN or Ni alloys and ceramics. Often the adhesion of the ceramic layer on the steel surface is not sufficient. 

Izumi K., Murakami M., Deguchi T., Morita A., Tohge N., Minami T. Zirconia coating on stainless steel from organ zirconium compounds. J. Am. Caam. Soc. 1989 72(8) 1465-1468 Izumi K., Tanaka H., Uchida Y., Tohge N., Minami T. Hydrolysis of trifunctional alkoxysilanes and corrosion resistance of steel sheets coated with alkoxysUane-daived films. J. Mater. Sci. Lett. 1993 12 724-727... 

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