Self-Warning and Self-Repairing Mechanisms in Functional Coatings: A Review

Coatings have attracted widespread attention in the field of corrosion protection of metals because of their corrosion resistance and convenient techniques. Unfortunately, till now, traditional coatings have the shortcomings of vulnerability and passive corrosion protection, hence functional coatings progressively replace them. Endowing coatings with additional functions not only transform them into active protection mechanisms but also significantly improve life cycle of coatings. However, there is only limited success in combining multiple functions of coatings, which poses considerable obstacles to further advancement of their application researches. In this paper, we summarize the research progress of self-warning and self-repairing coatings in the field of metal corrosion protection as much as possible from the perspective of functional material selection. Meanwhile, the current progress of substituting dual-functional coatings for single-functional coatings is also highlighted. We aim to provide more options and strategic guidance for the design and fabrication of functional coatings on metal surfaces and to explore the possibilities of these designs in practical applications. Last but not least, the remaining challenges and future growth regarding this field are also outlined at the end. It is hope that such an elaborately organized review will benefit the readers interested to foster more possibilities in the future.