Microstructure and corrosion behavior of ALD Al2O3 film on AZ31 magnesium alloy with different surface roughness

There remains growing interest in magnesium(Mg) and its alloys, as they are the lightest structural metallic materials and potential metallic biomaterials. In spite of the greatest historical Mg usage at present, the wider use of Mg alloys remains restricted by the poor corrosion resistance. A nano amorphous film, as the composition of Al2O3, had now been deposited on the AZ31 Mg alloy substrate by atomic layer deposition(ALD). Grazing incidence X-ray diffraction(GIXRD), X-ray reflectivity(XRR), X-ray photoelectron spectroscopy(XPS), atomic force microscope(AFM) and scanning electron microscopy(SEM) had been employed to identify the chemical compositions, microstructure and Al2O3/Mg interface of specimens firstly. Then corrosion behavior had been evaluated by neutral salt spray test and electrochemical measurement. The results showed that nano amorphous film made a homogeneous cover on Mg alloy. The film could improve the corrosion resistance of Mg alloy greatly, not only with a positive shift in E corr and a decrease in i corr, but also with a more uniform corroded mode. Furthermore, the roughness was found to be an important factor for corrosion resistant, in the way that rougher surface was corroded worse, and greater improvement would be in corrosion resistant after nano amorphous film deposition.