**5. Metal corrosion and self-healing coatings**

As stated before, self-healing materials offer vast scientific attention due to the wide range of applications. In recent years, these new-generation protective coatings have been developed and commercialized for metal corrosion. In this regard, selfhealable polymers find potential candidates for coatings due to their suitable thermomechanical behavior, lightweight, excellent adhesion, corrosion resistance, and good chemical resistance [43]. The major components of all coatings are the binders. So, it is obvious that the selection of the binder will affect the general performance of the coating. The most common binders are epoxy resin and polyurethane, however many other polymers, such as acrylic resins and polyesters, are used in many applications [44]. One of the most convenient methods proposed for self-healing coatings is adding containers loaded with a self-healing agent to a polymeric matrix (binders). Self-healing coatings can remarkably enhance the anti-corrosion performance and service life of metals. These protective coatings can restore the physical coating barrier, seal or close defects, or even inhibit the corrosion reactions at the coating defects. This is mostly accomplished by adding microcapsules loaded by a polymerizable healing agent or corrosion inhibitors to routine binders. The other self-healing design strategies are less commonly reported and therefore they are not discussed in this chapter. It is also worth noting that the coatings described here are mainly epoxy- or polyurethane-based organic systems. Two main classifications can consider for selfhealing coating, autonomous and non-autonomous. In the following section, these two mechanisms are discussed in detail.
