**5.1 Autonomous healing mechanisms**

Autonomous self-healing coating can repair their bulk integrity or functional properties without any external physical intervention. The Autonomous healing ability is usually achieved by embedding extrinsic polymerizable healing agents in the coating. In this system healing agents are mostly stored in microcapsules and released when the coating is damaged, which then polymerizes to fill the damage or form a protective film that inhibits the electrochemical reactions occurring at the exposed metal substrate [18].
