The influence of graphene content on the anti-corrosion performance of graphene/TiO2 water glass substrate composite coatings

A composite anti-corrosion coating with five different graphene ratios was coated on the surface of 2A12 aluminum alloy, using graphene/TiO 2 mixed powder as the anti-corrosion filler and K 2 SiO 3 water glass as the matrix. Scanning electron microscope (SEM) and X-ray diffractometer (XRD) were used to characterize the microscopic morphology, element composition, and phase composition of coatings. The corrosion resistance of the coating was appraised using electrochemical characteristics such as AC impedance and polarization curves. The surface of the coatings with low graphene content is dense and level. The surface of coatings with graphene content exceeding 0.5 g (2.5 wt.%) exhibit large-sized pits and cracks, and large corrosion products are produced after immersion in 3.5 wt.% NaCl solution. All five coatings maintained a stable phase structure before and after corrosion. Electrochemical analysis shows that the increase in graphene content leads to a first strong and then weak physical barrier effect of the coating against corrosive media. The coating with 0.25 g(1.25 wt.%) graphene exhibits the best corrosion resistance, with its |Z| 0.01H z value maintaining around 10 5 Ω·cm². When the graphene content exceeds this value, the inhibition of the coating on corroding media will be weakened by reason of particle aggregation.