Surfactant-modified ZnO NPs enhance the corrosion barrier performance of PLA coatings on AA2024-T3 aluminum alloy

This work reported the fabrication of ZnO nanoparticles, which were then modified using surfactants to enhance the anticorrosion performance of polylactic acid (PLA) coatings on AA2024-T3 aluminum alloy. Surfactant-modified ZnO nanoparticles were synthesized under alkaline conditions via a precipitation method using cetyltrimethylammonium bromide (CTAB) and polyethylene glycol (PEG) to generate mesoporous structures. BET analysis revealed type IV isotherms with distinct mesoporous features, where ZnO/CTAB exhibited a higher specific surface area (10.63 m 2 /g) and smaller mesopore size (~11 nm), while ZnO/PEG produced larger pores (~34 nm) with a lower surface area (3.49 m 2 /g). The incorporation of surfactant-modified ZnO into PLA significantly enhanced corrosion resistance in 1 M HCl, with PLA/ZnO/CTAB exhibiting higher inhibition efficiencies (99.36% Tafel; 87.4% EIS) than PLA/ZnO/PEG (99.31% Tafel; 85.3% EIS). Electrochemical analysis indicated a positive shift in corrosion potential, a reduction in corrosion current density, and an increase in charge transfer resistance. Additionally, water contact angle measurements indicated enhanced surface hydrophobicity (>94°), suggesting reduced electrolyte wettability. The enhanced anticorrosion performance is attributed to a synergistic mechanism wherein the presence of mesoporosity facilitates homogeneous nanoparticle dispersion and establishes highly tortuous diffusion pathways, while increased hydrophobicity suppresses electrolyte uptake and ion transport through coating defects. These findings highlight the pivotal role of the interplay between mesoporosity and hydrophobicity as a design principle for the development of high-performance and environmentally benign PLA-based coatings for aerospace aluminum alloys.