Electrodeposition of TiO2 layer-by-layer assembled composite coating and silane treatment on Mg alloy for corrosion resistance

The layer-by-layer (LbL) assembly approach is a versatile way for the construction of multilayered nanoparticles coating. We demonstrated that the TiO2 nanoparticles could be assembled on magnesium (Mg) alloys via the modification of opposite charged poly(styrenesulfonate) and polyethylenimine. Adsorption of the polyelectrolyte layer occurred in the beaker where particles and the selected polyelectrolyte solution were mixed, creating a layer of polyelectrolyte on the nanoparticles. Then these surfaced-modified nanoparticles were LbL assembled on the Mg alloy by electro-deposition. Finally, the surface silanization would prevent the peeling off of the TiO2 nanoparticles and leads to stable assembly. The coated samples were examined using field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The corrosion of the alloys was examined using potentiodynamic polarization, electrochemical impedance spectroscopy. The results show that a well-controlled and integrated silanized LbL system has been constructed via PMTMS and polyelectrolyte modified nanoparticles, which could provide good protection for Mg alloys.