Incorporating SiO2 functionalized g-C3N4 sheets to enhance anticorrosion performance of waterborne epoxy

Abstract In this work, a series of waterborne epoxy coatings containing g-C3N4@SiO2 composites were developed to evaluate the anticorrosion property on mild steel. The SiO2 nanoparticles precipitated on g-C3N4 sheets were fabricated via a facile sol-gel method applying tetraethoxysilane (TEOS) as precursor. With the SiO2 served as functionalized spacer between g-C3N4 sheets, the dispersibility of modified g-C3N4 sheets in epoxy matrix was notably strengthened. Especially, the g-C3N4 sheets functionalized with SiO2 endowed improved interfacial interaction bonding and compatibility between g-C3N4@SiO2 and epoxy, leading to the significant increase in anticorrosion properties. The characterizations of g-C3N4@SiO2 were investigated adequately, and scanning electron microscopy (SEM) was applied to prove the predominant dispersing performance of g-C3N4@SiO2 in epoxy coating. Furthermnore, to confirm effect of g-C3N4@SiO2 nanocomposites on the anticorrosion and barrier performance of waterborne epoxy, electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and salt spray test were conducted to estimate corrosion resistances of the g-C3N4@SiO2/epoxy. The obtained data revealed that the |Z|0.01Hz value of g-C3N4@SiO2 coating increased by 969 % compared with neat epoxy coating. Additionally, the 0.3 wt.% additive amount of g-C3N4@SiO2 was confirmed to provide the best shielding effect in epoxy coating, attaining the highest corrosion resistance among the composite coatings.