Smart-Sensing Polymer Coatings with Autonomously Reporting Corrosion Dynamics of Self-Healing Systems

Inspired by biological systems, self-healing coatings have been fabricated to protect metals against corrosion. However, in situ monitoring of the corrosion dynamics for various self-healing strategies generally remains a big challenge due to different working mechanisms. In the present work, a universal intelligent-sensing coating (SC) system containing pH-responsive polymer microspheres with a color probe is developed. When corrosion occurs in the self-healing system, the color around cracks turns pink gradually over time owing to the increased pH value. For the high-performance self-healing coatings, the onset and propagation of corrosion is suppressed, thereby leading to a narrow light-pink-color area. With this smart SC approach, the corrosion dynamics is established for three self-healing strategies by the correlation between the width of color lines with time. The anticorrosion ability in 48 h for the three extrinsic self-healing strategies are evaluated; that is, the SC with benzotriazole-loaded poly(divinylbenzene)-graft-poly(divinylbenzene-co-acrylic acid) microspheres (PDVB-graft-P(DVB-co-AA)-BTA) is superior to that with BTA-loaded halloysite (Halloysite-BTA), which surpasses that with polyurethane/poly(urea-formaldehyde) microcapsules filled with isophorone diisocyanate (IPDI@PU/PUF). These results are consistent with electrochemical experiments. This smart-sensing coating system can be a promising alternative for the in situ investigation of the anticorrosion performance of various self-healing anticorrosion strategies.