Effect of silicate concentrations on nanostructure and corrosion performance of oxide coatings on aluminum by plasma electrolytic oxidation

ceramic coatings are fabricated on pure aluminum by plasma electrolytic oxidation (PEO)in four kinds of electrolyte systems[phosphate-phosphat/silicate(2g/l)-phosphate-silicate(8g/l)-silicate].Effect of silicate concentrations on nanostructure and corrosion performance of PEO coatings were examined by means of scanning electron microscopy , x-ray diffraction, potentiodynamic polarization in 3.5% NaCl solution. The results showed that PEO films obtained in solutions with 8g/l silicate had better corrosion resistance. Phosphate/silicate (8g/l) electrolyte in comparison to phosphate, silicate and phosphate/silicate (2g/l), had lower porosity and cracks. Corrosion resistance of phosphate/silicate (8 g/l) electrolyte was higher than other electrolytes