MICROSTRUCTURE AND CORROSION PERFORMANCE OF SILICA COATINGS ON ALUMINUM SURFACE PREPARED BY PLASMA ELECTROLYSIS TECHNIQUE

Abstract Silica phases were precipitated on aluminum surface by potentiostatic plasma electrolysis technique. Aqueous sodium silicate solutions with different concentrations were used for this purpose. SEM, EDS, XRD, surface profiles and polarization curves were used to study coatings properties. The results showed that the growth of the silica containing phases on aluminum surface was promoted by increasing sodium silicate content of the electrolyte. However, in very high concentration solutions, the morphology of the oxide films changed and the roughness of the coating increased. Moreover, the amorphous compounds were substituted for crystalline phases. Coated specimens showed high corrosion resistance in 3.5 % NaCl media