Investigation of Mixed-Type Craters and the Role of Bifluoride Additives to Produce Zirconia-Toughened Alumina-Based PEO Coating
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Al2O3-ZrO2 composite ceramic coatings were prepared on Al6061 aluminum alloy by plasma electrolytic oxidation in Na3PO4-K2ZrF6-Na2SiF6-based alkaline electrolyte. Optimum processing time for the coating formation was found to be ~ 50 min. Cross section and surface morphology of the coatings were analyzed using scanning electron microscope. From the phase and elemental composition analysis, the presence of m-ZrO2 and t-ZrO2 phases was confirmed. It was further observed that the peak intensities of t-ZrO2 and α-Al2O3 phases increased with processing time, which was attributed to the enhanced crystallinity caused by the efficient sintering conditions. Corrosion properties were investigated by potentiodynamic polarization test in 3.5 wt.% NaCl solution. The results showed high improvement in corrosion rate with minimum recorded value ~ 0.25 mmy (mm/year) and corrosion current ~ 0.15 × 10−6 A/cm2.
Keywordscorrosion K2ZrF6 microstruture PEO zirconia-toughened alumina
This work was supported by the National Research Foundation of Korea (NRF) Grant funded by the Korea government (MSIP) (No. 2011-0030058).
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