Formation of ZrO2–SiC Composite Coating on Zirconium by Plasma Electrolytic Oxidation in Different Electrolyte Systems Comprising of SiC Nanoparticles

Plasma electrolytic oxidation (PEO) coupled with electrophoretic deposition (EPD) was used to fabricate ZrO2/SiC composite coating on the zirconium metal. The PEO–EPD process was carried out in three different electrolyte systems consisting of 5 g/l sodium aluminate or trisodium orthophosphate or sodium metasilicate with 4 g/l SiC nanoparticles. The X-ray diffraction results indicate monoclinic zirconia is the major phase in phosphate and silicate electrolyte while the coating produced in aluminate electrolyte is composed of tetragonal zirconia. The potentiodynamic polarization studies (PDP) indicate that composite coating produced in phosphate + SiC nanoparticle containing electrolyte exhibit superior resistance to corrosion, which can be attributed to the pore-free morphology of the coating. All the PEO–EPD coatings show exceptionally good adhesion strength (Lc  > 40 N). The coating fabricated in phosphate + SiC nanoparticles is found to be the best coating because of its superior resistance to corrosion and reasonably good adhesion strength.