Adapted synthesis routes and healing evaluation of a self-healing anticorrosive coating

In the past two decades, self-healing coatings have emerged as a potential alternative approach to enhance the life span of structural metal components constantly exposed to aggressive environments. In this work, we aimed to obtain capsules smaller than 1 µm containing an appropriate amount of oil seeking to provide efficient self-healing. A modification in the route of synthesis of self-healing coating capsules is proposed. This modification of a typical synthesis route, which consisted of introducing an additional mechanical agitation step before adding a formaldehyde aqueous solution, was used to entrap linseed oil as a healing agent in poly(urea–formaldehyde). Hence, two synthesis routes were investigated: one involving mechanical agitation at high-speed rotation and another which combines mechanical and ultrasonic agitation. The capsules obtained by agitation had average sizes of 0.35 ± 0.13 and 0.37 ± 0.19 µm and an oil content of 80 ± 2.2 and 77 ± 1.7 wt%, respectively. Both were incorporated, separately, into an epoxy resin matrix, and the composite was applied onto ASTM A36 steel plates for evaluation of healing crack filling performance and accelerated corrosion testing. Scanning electron microscope images showed that the two coatings had a similar healing effect, mainly due to their similar estimated oil content.