Environmentally friendly expanded graphite-doped ZnO superhydrophobic coating with good corrosion resistance in marine environment

Designing and fabricating the marine anti-corrosion materials without fluorine by superhydrophobic method is a huge challenge. In this study, an environmentally friendly composite coating was prepared by combing modified expanded graphite(EAG) with nano zinc oxide(ZnO). This coating showed superhydrophobic surface and good corrosion resistance. Fourier transform infrared spectroscopy(FITR), X-ray diffraction(XRD),and scanning electron microscopy(SEM) were used to characterize the materials in fabricating process of the coating. The properties of three composite coatings(ZnO,EAG, and EAG@ZnO) were analyzed, including surface roughness, water contact angle, corrosion resistance, selfcleaning and anti-fouling. The combination of ZnO and EAG caused a big water contact angle, leading superhydrophobic surface of the composite coatings. The electrochemical results showed that the superhydrophobic EAG@ZnO coating had a larger capacitive arc diameter and charge transfer resistance, indicating the enhanced anti-corrosion resistance. Meanwhile, the EAG@ZnO coating also showed good self-cleaning and anti-fouling performance according to solid and liquid pollutants tests.In addition, the mechanical properties and stability of the superhydrophobic EAG@ZnO coatings were evaluated by knife peeling and finger scratch tests. In summary, these superhydrophobic and anti-fouling EAG@ZnO composite coatings provide a potential application in marine corrosion and protection field.

Corrosion behaviors for peak-aged Mg-7Gd-5Y-lNd-0.5Zr alloys with oxide films

The corrosion behaviors of T5 （225 ℃, 6.5 h） and T6 （460 ℃, 2 h ＋ 225 ℃, 12 h） peak-aged Mg-7Gd- 5Y-1Nd-0.5Zr alloys with oxide films were investigated by optical microscope （OM）, scanning electron microscopy （SEM）, and energy-dispersive spectroscopy （EDS）. The weight loss rates and electrochemical tests were also analyzed. The thicknesses of T5 and T6 oxide films are roughly 0.6 and 1.0 μm, respectively. The components of oxide films mainly consist of O, Mg, Y, Nd, and Gd, and the T6 oxide film results in surfaces with larger peaks than T5 oxide film. In addition, Y, Nd, and Gd peaks are all higher than those of Mg-7Gd-5Y- 1Nd-0.5Zr alloys, but Mg peak is consistently far below than that of the alloys. The specimens could be arranged in de- creasing order of corrosion rates and corrosion current densi- ties： T6 oxide film 〈 T5 oxide film 〈 T6 without oxide film 〈 T5 without oxide film. The oxide films are compact to increase the corrosion resistance for Mg-7Gd-5Y-1Nd-0.5Zr alloys, which will provide a guiding insight into the corrosion and protection of Mg-RE alloys in atmospheric environments.