Autonomous-healing and smart anti-corrosion mechanism of polyurethane embedded with a novel synthesized microcapsule containing sodium dodecyl sulfate as a corrosion inhibitor

The self-healing and smart anti-corrosion behavior of a polyurethane coating enhanced with micro-sized capsules have been investigated. An in situ polymerization technique was employed to synthesize a novel microcapsule containing sodium dodecyl sulfate (SDS) as a corrosion inhibitor in linseed oil (LO). FE-SEM, FT-IR and TG analysis were used to characterize the prepared microcapsules. The capsules were separately embedded in polyurethane at 1, 4 and 7 wt% and the coating properties were investigated through the water absorption rate and pull-off adhesion strength. The scratched coating was then subjected to 3.5 wt% NaCl solution to investigate the self-healing ability. Electrochemical measurements were carried out by means OCP, EIS and potentiodynamic polarization and the inhibition mechanism of SDS was discussed in terms of interfacial interactions. Despite the adhesion strength, a positive effect was observed for the water uptake, after addition of the microcapsules. 4 wt% of LO/SDS microcapsules showed the best results as its inhibition efficiency was more than 90% compared to single linseed oil capsules. EDS mapping was also employed to verify the successful release and distribution of the SDS, when subjected to scratching.