Abstract
This chapter discusses a modified microarc oxidation (MAO) process using two kinds of nano-additives (Al2O3 and NaF) doped in the alkaline electrolyte system in order to improve the performance of MAO ceramic coatings formed on magnesium alloy AMS4429. The surface morphology, phase composition, and elemental composition of the MAO ceramic coating were examined by field electron emission scanning electron microscopy, X-ray diffraction, and energy-dispersive X-ray spectroscopy. electrochemical impedance spectroscopy and potentiodynamic polarization techniques were used to investigate the electrochemical behavior of MAO coatings. Results showed that the ceramic coatings formed are composed of pure MgO with porous surface structures. Nano-additives showed no significant effect on the elemental composition, while they strongly influenced the morphological features and corrosion resistance of the MAO coating formed. The addition of NaF to the electrolyte solution results in the formation of MAO coatings with finer uniform nodules than that of Al2O3 nanoparticles leading to a successful protective MAO coating.
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