Sustainable Self-Healing Coatings: Optimizing Microencapsulation of Biodegradable Linseed and Hemp Seed Oils for Enhanced Corrosion Protection

Corrosion is one of the biggest challenges in metal surfaces, especially when scratches and impacts damage the coating. Self-healing agents in the coating ensure long-term protection, effectively shielding the metal from corrosion. However, these materials are not environmentally friendly in general. To improve sustainability, we propose encapsulating renewable and biodegradable natural drying oils (linseed and hemp seed oils) to enhance the self-healing properties of the coatings. In-situ polymerization of these urea-formaldehyde microcapsules was performed at 60 °C using different stirring rates (200, 300, and 400 rpm). The structural, morphological, and thermal analyses were carried out by using Fourier Transform Infrared Spectrometer (FTIR), Scanning Electron Microscope (SEM), and Thermogravimetric Analysis (TGA). The particle size and oil content measurements were also performed. It was observed that a 300-rpm stirring rate resulted in optimum morphology, particle size, and oil content. 10 wt% microcapsules containing pure epoxy coatings were successfully applied to metal surfaces. It was observed that coatings with microcapsules provided better surface protection compared to pure coatings, and linseed oil-loaded microcapsules outperformed hemp seed oil-loaded microcapsules. These materials hold promise for future self-healing applications that are both effective and environmentally friendly.