Water-based epoxy coatings with pH-sensitive TiO2 containers for active corrosion protection of carbon steel

Smart containers can be produced with polyelectrolyte multilayers that can release inhibitors in response to environmental changes at the coating defects. In this study, mesoporous TiO2 hollow spheres were adopted as carriers for the encapsulation of corrosion inhibitor. The inhibitor-loaded TiO2 containers were modified by polyelectrolyte shells using layer-by-layer self-assembly technology. The release behaviour of the encapsulated inhibitor was investigated using UV–visible spectroscopy. Corrosion protection performance of the epoxy coating with polyelectrolyte-modified TiO2 containers was studied using electrochemical impedance spectroscopy and scanning Kelvin probe (SKP) techniques. Epoxy coating with the polyelectrolyte-modified TiO2 containers provided better barrier properties than that of the blank coating. Waterborne epoxy coating impregnated with the polyelectrolyte-modified TiO2 containers presented a significant self-healing effect after immersion in 0.5 M NaCl solution from the SKP results.