Smart anti-corrosive self-healing coatings using halloysite nanotubes as host for entrapment of corrosion inhibitors

An attempt was made to develop thin film self-healing coatings doped with halloysite nanotubes as host to entrap corrosion inhibitor (benzotriazole); that has an ability to release in a controlled way. The halloysite nanotubes are naturally available alumino-silicate hollow cylinders having 15 nm lumen diameter and 0.5-1.0 micron length. The corrosion inhibitors were loaded into the hollow lumens of halloysite (in acetone medium), which enables higher loading and sustainable release of inhibitor, due to its high aspect ratio. The inhibitor-loaded halloysite nanotubes were doped in the epoxy-silane coating at different loading levels. The ability of these nanotubes to release the corrosion inhibitors as and when required suppressed the anodic activity, thereby preventing the coating from further damage, and restricting the corrosion process. The smart self-healing anticorrosion performance of the epoxy-silane coating loaded with varying amount of halloysite entrapped benzotriazole was investigated on the mild steel substrate by direct exposure to corrosive media. The kinetics of the corrosion protection of the coating at the coating defect was analyzed by scanning vibrating electrode technique (SVET) and electrochemical impedance spectroscopy (EIS). The results confirmed the considerable improvement in the corrosion resistance due to the release of inhibitor from the doped halloysite.