Tailoring disulfide-embedded lignin-based hydrophobic self-healing coatings for metal protection

Green self-healing coatings, particularly lignin-based coatings, represent a breakthrough solution for sustainable metal protection and serve as a promising alternative to traditional petroleum-derived coatings. However, the practical application of pure lignin coatings is limited by their inherent structural rigidity and low hydrophobicity. To address these challenges, a series of lignin-based hydrophobic self-healing coatings were developed by functionalizing lignin with methacrylate groups, conjugating it with corrosion inhibitors, and subsequently polymerizing it with bis(2-methylacrylyl) oxyethyldisulfide (BMOD) and hydrophobic monomers. Through a systematic optimization, we achieved a contact angle of 115° and an E_corr of -20 mV for a coating with thickness ∼ 19 μm. Notably, this coating reduces the corrosion rate (CR) by over 6000 times compared to bare steel. Additionally, the coating is able to restore its microcracks under mild conditions through a combination of the gradual release of corrosion inhibitors and reversible disulfide bonds, achieving a healing efficiency of 83.3 % within 72 h. The combination of excellent hydrophobicity, self-healing capability, and corrosion resistance represents a significant advancement in environmentally friendly, durable coatings with extensive industrial applications.