Novel self-healing anticorrosion coating based on L-valine and MBT-loaded halloysite nanotubes

This work creatively utilized the pH-dependent electrostatic interactions between L-valine (L-Val) and halloysite nanotubes (HNTs) to fabricate pH-responsive anticorrosion materials and compared with 2-mercaptobenzothiazole (MBT)-loaded HNTs, which were assembled via layer-by-layer (LbL) self-assembly. These two methods can achieve controlled release of inhibitors and self-healing performance. However, the loading capacity of L-Val-loaded HNTs is higher than that of MBT's. There are 12 and 7 wt%, respectively. The pH-responsive release property was systematically evaluated by ultraviolet-visible (UV/Vis) spectrophotometry measurement. It demonstrates that 98% of adsorbed L-Val molecules released from HNTs within 300 min at pH 10 while the loaded MBT needs 120 h to achieve the equal ratio. Moreover, the difference of the release rate has a significant impact on the artificial crossed scratch experiment and shows a great performance gap in photographs. By comparing electrochemical impedance spectroscopy (EIS) data of three epoxy coatings, it can be seen that the epoxy coating, which was mixed with L-Val-loaded HNTs, shows a better anticorrosion ability than the epoxy coating contains MBT-loaded HNTs after immersion in 3.5 wt% sodium chloride solution for 96 h. Crucially, the pH-responsive anticorrosion material we fabricated can offer a rapid self-healing performance when the coating damaged by mechanical scratch via visual test and atomic absorption spectroscopy.