The development of sustainable corrosion-protective coatings from renewable feedstocks has attracted growing interest as an alternative to conventional petroleum-based systems. In our earlier work, we investigated bio-based coating platforms derived from cyclic carbonated vegetable oils, particularly cyclic carbonated soybean oil (CSBO), for the preparation of non-isocyanate polyurethane (NIPU) and hybrid networks with promising corrosion resistance on aluminium substrates. Building on these findings, the present study explores cardanol-based coatings as a complementary bio-derived approach for advanced surface protection.

Cardanol, obtained from cashew nut shell liquid, possesses a unique molecular structure comprising an aromatic ring and a long hydrophobic aliphatic side chain, making it an attractive precursor for protective coating applications. These structural features are expected to enhance coating hydrophobicity, barrier performance, and resistance to electrolyte ingress, all of which are critical for long-term corrosion mitigation. Drawing from our previous understanding of bio-based network formation, curing behavior, and coating–substrate interactions, this work examines how cardanol-based chemistry can be leveraged to achieve durable and environmentally responsible corrosion protection.

The study correlates the present cardanol system with our prior investigations on CSBO-based NIPU and hybrid coatings, with emphasis on coating formation, structural evolution, and electrochemical performance. The coatings are evaluated using FTIR, thermal analysis, surface wettability, morphology, electrochemical impedance spectroscopy, and polarization measurements to establish structure–property–performance relationships. Overall, this work highlights cardanol as a promising renewable building block for corrosion-resistant coatings and demonstrates how insights from earlier vegetable-oil-based systems can guide the design of next-generation sustainable protective materials for metallic substrates.