Fabrication of agro by-product derived green polyurea coatings with zero-VOC to combat corrosion and bacterial growth: A clean approach

Volatile organic compound (VOC) and crosslinker-free anti-corrosive polyurea (CPUrea) coatings have been developed using cardanol, formaldehyde, and urea through an acid catalysed, solvent-free in-situ approach for the first time. The high-performance of the optimized coating was reported after analytically comparing three compositions of the resin, namely CPUrea1.0, CPUrea1.2, CPUrea1.4, along with other relevant compositions (CPUrea0.6 - 0.8). The physico-mechanical tests and thermo gravimetric analysis suggested the superiority coating performance of CPUrea1.0 resin. The excellent combination of higher thermal stability (>300 °C) with flexibility, toughness, surface hardness, and adhesive strength highlights the suitability of protective system. The impedance value of CPUrea1.0 revealed the ability to resist corrosive ions up to 18 days in acidic and saline and 16 h in an alkaline medium. The formation of a homogeneous compact 3D crosslinked structure was observed using scanning electron microscopy images and was schematically presented via., sufficient interaction between polar groups in the resin and metal substrate. The inhibition (50 mm) ability of the resin towards E. coli and S. aureus provided an edge to such sustainable coating materials. The overall results proved that cardanol can be employed as a versatile precursor for the development of green VOC-free CPUrea coatings for protective applications.