Supersonic atmospheric plasma sprayed ZrO2 and ZrB2-SiC/ZrO2 coatings on Cf/Mg composites for anticorrosion

To improve the corrosion resistance of the carbon fiber reinforced magnesium matrix composites (C-f/Mg composites), ZrO2 and ZrB2-SiC/ZrO2 composite coatings were prepared by supersonic atmospheric plasma spraying (SAPS) on C-f/Mg composites. The microstructure and phase composition of the coatings before and after the corrosion test were investigated. Open circuit potential and potentiodynamic polarization tests were measured at room temperature. Results revealed that the corrosion current density (i(corr)) of the ZrO2 coated C-f/Mg composites decreased by one order while the ZrB2-SiC/ZrO2 coated Cf/Mg composites reduced by two orders. Compared with Cf/Mg composites, the corrosion potential (E-corr) of the ZrO2 and ZrB2-SiC/ZrO2 coated C-f/Mg composites increased by 220.5 mV and 1021.8 mV respectively, indicating that the ZrB2-SiC/ZrO2 composite coatings greatly improve the corrosion resistance of C-f/Mg composites. The uniform distribution of the SiC particles with small grain size in ZrB2 is responsible for the densification of the coating. The ZrB2-SiC/ZrO2 composite coatings provide a barrier for the substrate to impede the entry of Cl- in the corrosion solution, thus exhibiting a better corrosion resistance than the ZrO2 coating.