"Smart" coatings for active corrosion protection based on multi-functional micro and nanocontainers

The application of organic coatings is the most common and cost effective method for corrosion protection and extension of service life of many metallic structures in corrosive environments. However, the degradation processes rapidly develop once the disruption of the protective barrier occurs. Therefore, an active protection based on the "self-healing" of defects in coatings is necessary to attain a long-term effect. The present paper brings a brief summary of recent works in the area of new multi-level protective systems, based on the controlled release of anticorrosion species from "smart" micro and nanocontainers incorporated into a polymer or hybrid coating matrix. Nanocontainer (or nanoreservoir) is a nanosized volume filled with an active substance confined in a porous core and/or a shell which precludes the direct contact between the active agent and the adjacent environment. Several types of nanoreservoirs of corrosion inhibitors, nanotraps and microcapsules with water displacers have been recently developed, incorporated into coating systems and assessed in terms of active corrosion protection. A multi-level self-healing approach combining several damage prevention and restoration mechanisms within the same system, including the entrapment of corrosive ions, corrosion inhibition and water displacement from active defects, is here reviewed. (c) 2012 Elsevier Ltd. All rights reserved.