Lignin/Fe3+ Coordination Networks via PDA/PEI Co-Deposition: A Green Strategy for Multifunctional Coatings

Mechanical components made of aluminum suffer from severe friction, wear, biofouling, and corrosion, yet existing coatings often fail to maintain stable tribological performance under cyclic loading. In this study, a nature-inspired multifunctional coating was fabricated on aluminum via co-deposition of lignin, Fe 3+ , dopamine, and polyethyleneimine (PEI). The Fe 3+ ions coordinate with phenolic hydroxyl groups in lignin while simultaneously participating in Michael addition and Schiff-base reactions with DA and PEI, forming a dense crosslinked network. With an optimal lignin content of 5 wt% (L 5 /DA/PEI), the coating exhibits a significantly reduced coefficient of friction (0.43–0.46) and superior wear resistance, attributed to the lubricating boundary film formed by oxygen-containing groups in lignin. The same coating also demonstrates outstanding adhesion (96.97% residual area) and excellent corrosion resistance in 3.5% NaCl solution. Meanwhile, the coating with 10 wt% lignin (L 10 /DA/PEI) displays remarkable antimicrobial activity against both Staphylococcus aureus and Escherichia coli , benefiting from enhanced Fenton-like reactions that generate toxic hydroxyl radicals. The findings open new avenues for designing eco-friendly, multifunctional protective surfaces for durable aluminum components under complex service environments.