Abstract
The effect of Na2SiO3 concentration on the dense ceramic oxide coatings prepared on a AZ31 magnesium alloy through electrolytic plasma processing in a NaOH-Na2SiF6 electrolytic solution, have been investigated. The x-ray diffraction (XRD) results showed that the coating formed in silicate electrolyte was mainly composed of MgO, Mg2SiO4. Scanning electron microscopy (SEM) micrographs reveals that the number of pores on coatings decreases by increasing concentration of Na2SiO3 and coatings prepared in 12-20 g/L of Na2SiO3 show similar surface morphologies. The observed micro-hardness of coating layers is over 1000 Hv, which is much larger than that of the original AZ31 magnesium alloy without electrolytic plasma processing.