In order to improve the anti-corrosive and anti-oxidative properties of electroless Ni-P coating (ENPC), a vanadium conversion coating (VCC) was fabricated on the surface of the ENPC. SEM images and EDX line scanning spectra indicate that as-prepared VCC is supposed to be a thin film with a thickness of a few nanometres. XPS analyses demonstrate that the VCC is mainly consisted of V 2 O 5 or V 2 O 5 •nH 2 O. The acid exposure test data indicate that the VCC-treated ENPC, compared with the pristine one, demonstrates a highly enhanced antioxidative property. Furthermore, the result of neutral salt spray test manifests that the VCCtreated ENPC has also a highly enhanced anti-corrosive property, which is further confirmed by the result of electrochemical corrosion test.

The mechanical durability of a superhydrophobic aluminum alloy surface is an important indicator of its practical use. Herein, we propose a strategy to prepare a superhydrophobic 2024 aluminum alloy surface with highly enhanced mechanical durability by using a two-step chemical etching method, using a NaOH solution as the etchant in step one and a Na2CO3 solution as the etchant in step two. Robust mechanical durability was studied by static contact angle tests before and after an abrasion test, potentiodynamic polarization measurements after an abrasion test and electrochemical impedance spectroscopy tests after an abrasion test. Furthermore, the mechanism for enhanced mechanical durability was investigated through scanning of electron microscopy images, energy-dispersive X-ray spectra, Fourier transform infrared spectra and X-ray photoelectron spectra. The testing results indicate that a hierarchical rough surface consisting of regular micro-scale dents and some nano-scale fibers in the micro-scale dents, obtained with the two-step chemical etching method, contributes to highly enhanced mechanical durability. Meanwhile, the as-prepared superhydrophobic 2024 aluminum alloy surface retained a silvery color instead of the black shown on the superhydrophobic 2024 aluminum alloy surface prepared by a conventional one-step chemical etching method using NaOH solution as the etchant.