PFAS-free laser-textured triple-scale architectures for durable passivation against pitting corrosion of aluminum alloys

Scalable manufacturing of multifunctional metal surfaces requires precise control over surface topology, chemistry, and interfacial stability. Here, we report a nanosecond laser-enabled strategy integrating hierarchical structuring with PFAS-free chemical functionalization to engineer triple-scale architectures on AA6061 aluminum alloy. Nanosecond fiber laser texturing generated fully covered grid and grid-with-double-diagonal patterns composed of microscale trenches, submicron resolidified ridges, and nanoscale cauliflower-like features formed through photothermal melting and rapid solidification. The oxide-enriched laser-textured surface provided reactive hydroxyl sites that enabled covalent attachment of a non-fluorinated siloxane network through immersion-based OTS-PDMS treatment, producing a mechanically anchored hybrid layer. This morphology-chemistry coupling established a stable Cassie–Baxter wetting regime with water contact angles up to 158°, roll-off angles near 2°, and low contact angle hysteresis. The grid-with-double-diagonal architecture ensured uniform oxide modification and silane anchoring across large areas, demonstrating manufacturability. Electrochemical testing in 0.6 M NaCl showed significantly reduced corrosion current density, elevated pitting potential, and up to three orders-of-magnitude higher impedance than untreated aluminum, demonstrating durable interfacial performance in aggressive environments.