Water and oil wettability of anodized 6016 aluminum alloy surface

• Published in: Applied surface science 2017-11, Vol.422, p.430-442
• Main Authors: Rodrigues, S.P., Alves, C.F. Almeida, Cavaleiro, A., Carvalho, S.
• Format: Article
• Language: English
• Subjects: 6000 series aluminum alloys; Anodic aluminum oxides; Hydro/oleo-philic/phobic behaviour; Lubrication; Micro-nanostructuring
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2017.05.204

[Display omitted] •The water/oil wettability study of anodized high-alloyed aluminum surfaces.•Correlation of the Al oxides ordering with the liquid repellence encountered.•Thick porous oxides enhanced the surface wettability.•Dimple-shaped surfaces led to slight higher repellence of anodized surfaces. This paper reports on the control of wettability behaviour of a 6000 series aluminum (Al) alloy surface (Al6016-T4), which is widely used in the automotive and aerospace industries. In order to induce the surface micro-nanostructuring of the surface, a combination of prior mechanical polishing steps followed by anodization process with different conditions was used. The surface polishing with sandpaper grit size 1000 promoted aligned grooves on the surface leading to static water contact angle (WCA) of 91° and oil (α-bromonaphthalene) contact angle (OCA) of 32°, indicating a slightly hydrophobic and oleophilic character. H2SO4 and H3PO4 acid electrolytes were used to grow aluminum oxide layers (Al2O3) by anodization, working at 15V/18°C and 100V/0°C, respectively, in one or two-steps configuration. Overall, the anodization results showed that the structured Al surfaces were hydrophilic and oleophilic-like with both WCA and OCA below 90°. The one-step configuration led to a dimple-shaped Al alloy surface with small diameter of around 31nm, in case of H2SO4, and with larger diameters of around 223nm in case of H3PO4. The larger dimples achieved with H3PO4 electrolyte allowed to reach a slight hydrophobic surface. The thicker porous Al oxide layers, produced by anodization in two-step configuration, revealed that the liquids can penetrate easily inside the non-ordered porous structures and, thus, the surface wettability tended to superhydrophilic and superoleophilic character (CA