Corrosion and electrochemical behavior of water glass coatings embedded with graphite/titanium oxide on 2A12 aluminum alloy

Graphite/titanium oxide composite anti-corrosion coatings with five proportions of graphite were applied on the surface of aluminum alloy. The surface morphology and composition of the coating were analyzed by scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The crystal structure of the coatings was characterized by X-ray diffraction (XRD). The electrochemical properties of the coatings were tested by potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS). After immersing five graphite content coatings in 3.5% NaCl solution for 360 h, it was found that elements such as C, Si, and K in the coatings were consumed to some extent, but the phases in these coatings did not change. Electrochemical analysis showed that graphite content is an important factor affecting corrosion protection properties of the coating. A lower content of graphite (such as 0.25%, 0.5%, 2.5%) has a positive effect on corrosion resistance, and the |Z|0.01 of the coating before and after corrosion is maintained at about 105 Ω·cm2, which has a certain competitiveness. When the graphite content is increased (such as 5%, 10%), the corrosion resistance of the coating is weakened instead.