Electrodeposition of zinc and composite zinc–yttria stabilized zirconia coatings

Pure zinc and composite coatings of zinc and nano-sized yttria stabilized zirconia (YSZ) particles were prepared by cathodic electrodeposition from zinc sulphate-based electrolytes containing gelatin. The effects of gelatin on the morphology, crystallographic orientation of the zinc coatings and deposition mechanism of the composite Zn–YSZ coatings were studied. The coatings obtained were studied by scanning electron microscopy (SEM) with energy dispersion spectroscopy (EDS), X-ray diffraction and potentiodynamic polarization measurements. It was shown that the addition of gelatin to the electrolyte significantly changed the microstructure and crystallographic orientation of the zinc deposits and improved the coating microhardness. In the case of the composite coating co-deposition process, the YSZ particles were found to preferentially rest on the edges or macrosteps of the deposited zinc crystals. The incorporation of YSZ particles into the composite coating was enhanced by reducing the solution pH and through the addition of gelatin. The mechanical and electrochemical properties of conventional zinc coatings were observed to be significantly improved by the incorporation of YSZ particles.