Sustainable hydrophobic and strength film coatings for corrosion protection: Lignin biopolymer as an attractive film former on carbon steel- a way towards green chemistry

Lignin, an abundant byproduct of biomass processing, holds great promise for sustainable material applications. As a novel stride, in this study, pure lignin was extracted from raw Alfa fibers through a single, eco-friendly alkali treatment and assessed as both a green corrosion inhibitor and a coating precursor for carbon steel (CS). Electrochemical techniques revealed that the synthesized Alkali lignin (S-AL) achieved 92.9 % inhibition efficiency, surpassing commercial Alkali lignin (C-AL) by forming an adsorbed thin organic barrier on the CS surface. Harnessing this property, S-AL was spray-deposited into a uniform film whose high hydrophobicity (92.11°), low water uptake (10 %), and strong adhesion translated into superior long-term corrosion resistance. Structural and surface analyses (XRD, FT-IR, TGA, SEM-EDS, Zeta potential, and particle size) confirmed the purity of S-AL and the integrity of the coating. This waste-to-coating approach delivers a high-performance, sustainable alternative for steel protection. • Pure lignin was sustainably extracted from raw Alfa fibers via alkali treatment. • Synthesized lignin showed superior corrosion inhibition efficiency (92.9 %). • Lignin molecules form a protective barrier on carbon steel via surface adsorption. • Spray-coated lignin films provided effective anticorrosion protection, with SL/Xyl outperforming CL/Xyl. • SL/Xyl spray coated films exhibited excellent hydrophobicity, adhesion strength, and water resistance.