Active anticorrosion and self-healing coatings: A review with focus on multi-action smart coating strategies

The development of smart coatings with potential for active anticorrosion and self-healing protection of metals is essential for long-term performance of metallic structures in aggressive chemical environments. Presently, emphasis has been placed on the development of advanced smart coatings for corrosion protection in different applications. Innovative multifunctional coatings with fascinating stimuli-responsive functionalities are considered “smart”. The stimuli-responsive functionalities of these smart coatings when properly harnessed result in a class of coatings with inherent autonomous control of corrosion. Fundamentally, when metals are exposed to aggressive environments, occurrences at the metal-solution interface cause environmental changes. These changes can be controlled when triggers from external environment set off active components of smart coating, thereby enhancing coating's life and functionality. Common triggers include the availability of moisture, concentration of chloride ion, pH gradient, mechanical damage, impact, fatigue, light, redox activity and temperature. In this review, recent technological trends in active anticorrosion and self-healing coatings as functional routes for metal protection are summarized, stimuli responsiveness and mechanisms of inhibition are discussed, and recent multi-action protective systems are particularly focused on.