Anticorrosive performance of smart epoxy coatings with poly(urea-formaldehyde) (PUF) microcapsules filled with 5-ethylidene-2-norbonene (ENB)

In this study, poly(urea-formaldehyde) (PUF) microcapsules filled with 5-ethylidene-2-norbornene (ENB) were produced through in situ polymerization. The microcapsules were produced under nine different synthesis conditions based on a full factorial design, and subsequently incorporated into epoxy-based coatings. These coatings were applied to previously cleaned AISI 1020 steel substrates using the dip-coating method. The anticorrosive performance of the coatings was evaluated through immersion corrosion tests in a saline solution, after simulating damage through scratches. The results demonstrated satisfactory performance for coatings containing microcapsules synthesized under PUF/ENB 1 and PUF/ENB 9 conditions, which exhibited a more uniform dispersion of microcapsules. However, the PUF/ENB 2 samples displayed high microcapsule aggregation, which compromised their anticorrosive behavior and led to coating delamination after damage. Despite this, these samples still showed satisfactory corrosion resistance when compared to pure epoxy coatings. Scanning electron microscopy provided detailed insights into the interface between the coating and the metal substrate, reinforcing the corrosion test observations.