HYDROPHILIC NANOFIBER BARRIER COATINGS FOR ALUMINUM: WATERBORNE CROSSLINKING, MICROSTRUCTURE–PROPERTY LINKS, AND EIS-BASED PROTECTION

Abstract

Chromate-free corrosion control was realized by depositing waterborne, electrospun hydrophilic nanofiber mats onto a structural aluminum substrate, followed by dialdehyde-mediated thermal crosslink activation to stabilize the coating in aqueous media. Process-structureproperty relationships were established through SEM for fiber morphology, gel-fraction assays for network formation, DSC for crystallinity, ATR-FTIR for chemical signatures, and tensile testing for modulus and toughness, defining the coating as a polymeric barrier film within coating science. Electrochemical impedance spectroscopy in chloride solution tracked barrier evolution over extended immersion, and spectra were interpreted with equivalent-circuit models employing constant phase elements to decouple coating capacitance, pore resistance, and interfacial charge-transfer processes. A lower-temperature/longer-time curing route produced denser networks and more stable microstructures than a higher-temperature/shorter-time protocol, yielding markedly higher lowfrequency impedance and sustained barrier function relative to the bare alloy. Correlating reduced crystallinity and crosslink-driven stiffening with decreased electrolyte percolation explains the multi-fold improvement in protective performance, while morphology degradation and larger void pathways account for the less effective cure schedule. These results demonstrate a simple, scalable route to waterborne nanofibrous polymer coatings as chromate alternatives and outline a platform for advanced functionalities such as inhibitor-loaded, self-healing barrier systems.