Effect of different electrolyte systems on the micro-arc oxidation coatings of magnesium alloy
Three electrolyte systems were used to get micro-arc oxidation(MAO)of the AZ91 magnesium alloy.Scanning electron microscopy with an energy dispersive spectroscopy was used to observe the surface morphology and analyze the chemical compositions of the MAO samples.The phase structure of the coatings was characterized by the X-ray diffraction.The characteristics of the coatings by different electrolyte systems treated were compared by using the roughness,wetting angle and binding force.The corrosion resistance of coatings was investigated by the potentiodynamic polarization curves.Besides,the biodegradability of coatings was evaluated by the simulated body fluid(SBF)immersion experiment.The results showed that the micro-arc oxidation coatings had relatively strong binding force.The coatings obtained by different electrolyte systems had different surface morphologies and physical phases.The phosphate and silicate systems had a higher roughness,while the aluminate system had a lower roughness.The phosphate system had the smallest wetting angle and the aluminate system had the largest wetting angle.These differences resulted in phosphate system coatings being the most corrosion-resistant,silicate system coatings being the second most corrosion-resistant,and aluminate system coatings being the least corrosion-resistant.The surface of the coatings cracked after 21 days of SBF immersion,but the corrosion resistance were improved.This is due to the covering effect of corrosion products and calcium and phosphate deposits on the coating during the immersion process.
magnesium alloymicro-arc oxidationelectrolytessimulated body fluid immersion
NETL
NSTL
万方数据
维普
