Self-healing properties of protective coatings containing isophorone diisocyanate microcapsules on carbon steel surfaces

Microcapsules containing isophorone diisocyanate (IPDI) were used as self-healing additives in the alkyd varnish coatings (AVCs), and their self-healing performance was evaluated in the case of artificial defects on Q235 steel surfaces, using scanning micro-reference electrode technique and Fourier-transform infrared spectroscopy. Comparison of the micromechanical properties between the water-insoluble self-healing products (polyurethanes) and AVCs indicates that the former significantly enhanced the capability of the scratched crevice to successfully endure outer stress. The electrochemical impedance spectroscopy experiments analysed the different stages in the self-healing process. This study successfully demonstrated the self-healing activity of IPDI-AVCs in protecting steel surfaces.

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• We studied self-healing behaviour of AVC with IPDI microcapsules on Q235 steel.
• IPDI generates polyurethanes as self-healing products in the healed crevice.
• Self-healing products could bear much higher load force than the AVC.
• Self-healing products are more plastic than the AVC.
• Different stages of the continuously self-healing process are distinguished by EIS.