8 - Self-healing composite coatings with protective and anticorrosion potentials: classification by healing mechanism

Abstract

To mitigate corrosion, recent developments in coating technology have brought about newer fabrication designs for protective coatings with efficient barrier properties. However, most coatings gradually lose their corrosion resistance due to fatigue and contributions from environmental and mechanical stresses within their service environments. Without repairs, this gradually leads to premature coating failures. To avoid the high cost of replacement operations associated with recoating surfaces, smart coatings are now designed to self-heal from stress-induced cracks on demand, with minimal intervention. Beyond corrosion inhibition, outlines of recent research areas have been presented, including some advantages and limitations associated with self-healing mechanisms. These smart coatings repair inherent damages with negligible external intervention toward enhanced barrier performance over extended duration. It is the subsequent restoration of coating barriers that births the term, “self-healing.” Self-healing coatings (SHCs) are designed to mimic the self-repairing processes in natural materials, for example, bones and insect cuticles. Some experimental results featuring healing mechanisms based on polymerizable healing agents and corrosion inhibitors, regeneration of internal structures by external stimuli and dynamic reversible chemistry have been elaborately discussed, including the aspects of shape recovery effect. Present challenges and future perspectives have been reported with special enquiries into the designs of more barrier coatings with diverse self-healing mechanisms, utilization of photothermal fillers for outdoor coating applications, as well as sorting mechanical and conductivity defects in SHCs. Fabricating coating systems that are capable of self-mending inherent damages within their polymer networks is an innovative chemical repairing technique at the molecular level toward sustainable coating technology.