Saline-responsive triple-action self-healing coating for intelligent corrosion control

In this work, a triple-action self-healing coating was fabricated to promote the corrosion protection of carbon steel based on a shape memory polymer (SMP) epoxy coating and polyaniline/benzotriazole (PANI/BTA) nanocapsules. The PANI/BTA nanocapsules had dual functions: (1) PANI as a saline (NaCl)-responsive gatekeeper could achieve the controllable release of BTA corrosion inhibitors, which could adsorb on the metal surface to inhibit corrosion; (2) PANI can prompt the formation of Fe2O3 passive layer. Besides, the thermo-responsive SMP coating could narrow the scratch size after heating, which was beneficial to reduce the amount of corrosion inhibitors needed to fully cover the steel surface. Electrochemical impedance spectroscopy (EIS) measurements were performed to investigate the self-healing performance of the coatings containing different contents of PANI/BTA nanocapsules. Furthermore, the synergetic inhibition effects of PANI, BTA and SMP coating were demonstrated using scanning electrochemical microscopy. The results indicated that the healed 0.5 wt% PANI/BTA coating exhibited an excellent self-healing property and its self-healing efficiency was higher than 96%. The XPS results indicated that the Fe2O3 passive layer was formed in the scratched region to resist steel corrosion.