Enhanced corrosion resistance of HA/CaTiO3/TiO2/PLA coated AZ31 alloy

In order to reduce the corrosion rate of AZ31 alloy, Hydroxyapatite/calcium titanate/titanium dioxide/polylactic acid (HA/CaTiO3/TiO2/PLA) coating which aligned the advances of organic and inorganic coatings was successfully coated onto AZ31 alloy. To overcome the weak adhesion between HA and PLA layers, TiO2 interlayer was used as a transition layer to increase the adhesion strength of HA/PLA. By the way, CaTiO3 was formed on the interface of HA/TiO2 by the reaction of HA and TiO2 in the anneal process of TiO2. The inner HA layer was prepared by electro-deposition method subsequently with alkali-heat treatment, and the intermediate TiO2 layer as well as outermost PLA layer was prepared by dip-coating method. The surface characterization of samples was studied by Scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). And the analysis results manifested that a compact and uniform HA/CaTiO3/TiO2/PLA coating was obtained on AZ31 alloy. Immersion corrosion tests and electrochemical tests in Hank's solution at 37 degrees C were also conducted to study the corrosion behavior of AZ31 alloy, and the results indicated that HA/CaTiO3/TiO2/PLA coated AZ31 alloy exhibited superior corrosion resistance compared with that of HA /PLA coated sample. The adhesion mechanism of TiO2 interlayer and the degradation mechanism of coatings were discussed in this study. (C) 2015 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.