Developing a self-healing anticorrosion coating for steel protection in marine tidal zone

A self-healing anticorrosion protective was developed for steel st-37 exposed to the marine tidal zone, which is composed of a multi-layer polymer coating. The coating includes zinc-rich epoxy primer, self-healing microencapsulated embedded epoxy, and a top coat consisting of polyurethane incorporated with silica nanoparticles. The size of microcapsules decreased with increasing agitation during encapsulation, which varies from 4 to 43 mu m. Good performance was observed for producing the encapsulated particles with a size of up to 5 mu m and more than 90% loading of the embedded healing agent, in which a 1680 rpm agitation along with a pH of 3 for the synthesis environment and a 130 min for the synthesis duration is set. The optimal amount of microcapsules and silica nanoparticles was 10 and 1.5 wt%, respectively. Also, the promised self-healing anticorrosion coating leads the damaged areas to be fully healed in almost 12 h in the face of harsh conditions. In contrast to the non-self-healing one, the healing ability of the developed self-healing coating shows good barrier properties and leads to a lesser loss of interface adhesion. An epoxy/polyurethane coating system consisting of dual functions of self-healing and anticorrosion was developed for steel protection in marine tidal zone. The self-healing coating was able to repair completely artificial scratches in about 12 h. The polyurethane topcoat incorporated with silica nanoparticles showed good mechanical and thermal properties and these properties were improved by increasing the amount of nanoparticles. image