Enhanced Corrosion Resistance of a Double Ceramic Composite Coating Deposited by a Novel Method on Magnesium-Lithium Alloy (LA43M) Substrates

In this study, a composite coating with outstanding corrosion and wear resistance was successfully produced on LA43M substrates. The composite coating was composed of cold-sprayed aluminum, anodized Al₂O₃ and a SiO₂ sealing coating, which was defined as the MAC composite coating. The properties of the MAC composite coating were characterized by water contact angle, potentiodynamic polarization, salt spray corrosion test, electrochemical impedance spectroscopy and ball-on-disk test, while the microstructure was investigated by scanning electron microscope. The wear results show that the double ceramic composite coating improves the wear resistance compared to the LA43M substrate. After sealing with polysilazane, the surface of the MAC composite coating became hydrophobic. Thus, the corrosion current density dropped to 5.4 × 10⁻⁹ A cm⁻², which is by four orders of magnitude lower compared to that of the LA43M alloy. Furthermore, there was no significant change in surface roughness and profile after long-term corrosion test, demonstrating the outstanding corrosion resistance of the MAC composite coating. In addition, the MAC composite coatings presented the highest impedance loop, impedance moduli and the phase angles, hence confirming that the MAC composite coatings provided a high degree of corrosion resistance for LA43M alloy.