Hybrid coating of polydimethylsiloxane with nano-ZrO2 on magnesium alloy for superior corrosion resistance

To enhance the corrosion resistance of magnesium alloys , an organic-inorganic coating of polydimethylsiloxane (PDMS) hybridized with ZrO 2 nanoparticles is developed, where the PDMS is selected as the polymeric matrix for superhydrophobic surface, and nano-ZrO 2 particles as a physical barrier to strengthen and densify the polymeric matrix. The nanocomposite materials were characterized by field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectrophotometry (FT-IR), and X-ray diffraction (XRD). Electrochemical, dropping corrosion, and salt spray tests were carried out to evaluate the effect of the amount of ZrO 2 on the corrosion property of the PDMS-ZrO 2 coatings. Thermal stability, hydrophobicity , and corrosion resistance of the composite coatings are substantially improved by the introducing ZrO 2 modifier into PDMS matrix. Depending on the ZrO 2 content, the PDMS-ZrO 2 hybrids exhibit superior corrosion resistance, where the corrosion current density of PDMS-ZrO 2 coatings containing 10% (wt.%) ZrO 2 decreases about five orders of magnitude compared with Mg alloy substrate. Furthermore, it is noteworthy that ZrO 2 nanoparticles are filled in the PDMS matrix to provide a long-term protection in the salt spray test up to 210 h. The PDMS-ZrO 2 coatings demonstrate an excellent shielding ability for the Mg alloy, which is attributed to the strong hydrophobic surface of PDMS and compact network structure separated by the physical barrier of ZrO 2 nanoparticles in the PDMS chains. The proposed mixed matrix membrane guides a design direction for highly water-repellent coating with a long-term corrosion protection performance.