Preparation And Properties Of Superhydrophobic And Super Slippery Coating On Mg Alloy Surface

Superhydrophobic and lubricant-infused "super slippery" surfaces as special water-repellent wetting coatings have developed rapidly in recent years.Based on their antiwetting surface,they have satisfactory applications for self-cleaning,anti-corrosion,anti-icing,anti-fouling,drag reduction,oil/water separation and so on.Because of the low density,admirable ability of electromagnetic screening,high strength/weight ratio,recyclability and other advantages,Mg alloy is known as the green engineering material in the 21st century.However,shortcomings like easy of corrosion and fouling of magnesium alloy restrict its development.Constructing superhydrophobic or super slippery coating on Mg alloy surface could effectively solve the problem.In this study,via the hydrothermal synthesis,transition metal salt and stearic acid react on Mg alloy substrate to form superhydrophobic or super slippery film.The as-prepared surfaces were characterized by scanning electron microscopy(SEM),energy dispersive spectrometer(EDS),Fourier transformed infrared(FT-IR),X-ray photoelectron spectroscopy(XPS).Contact angle tester,low temperature freezing test,natural seawater immersion test and electrochemical test(EIS and IE)were used to study the long-term stability,anti-icing,antifouling and anticorrosion function of the prepared film.The superhydrophobic surface was prepared on AZ31 Mg alloy by one step hydrothermal method for cobalt sulfate reacting with stearic acid.The as-prepared surface showed repellency of aqueous solution with a static water contact angle of 158.6° and its superhydrophobicity was maintained for more than one year.The superhydrophobic surface showed anti-icing performance in a cold environment and improved corrosion resistance in 3.5 wt%NaCl solution.In this study,we aimed for higher efficiency and environmental friendliness to enhance the prospects for application of magnesium alloy.The stable double-layer hierarchical structure superhydrophobic coating was constructed on magnesium alloy surface via layer-by-layer assembled environmental-friendly method.The bottom layer was prepared by nickel sulfate and stearic acid reacted and the upper layer was constructed by cobalt sulfate and stearic acid synthesis,Compared with untreated magnesium alloy and single-layer superhydrophobic coating,the Mg alloy with dual-layer superhydrophobic coating showed improved corrosion resistance in 3.5 wt.%NaCl solution by electrochemical workstation test.The anti-fouling performance of the dual-layer superhydrophobic coating was determined by dropping fouled liquid and immersing in the natural seawater.The present study develops more possibilities to extend application of superhydrophobic surface.The superhydrophobic surface was formed by manganese sulfate and stearic acid reacted via hydrothermal method on the surface of Mg alloy,firstly.Then the lubricant-infused slippery surface was prepared on the basis of perfluoropolyether oil infusion.Through the comparative analysis of the contact angel of different kinds of surface at different time,the super slippery surface show perfect long-term stability.Furthermore,it can achieve self-repair through repeated immersion oil.The super slippery surface possessed larger impedance values through electrochemical impedance spectroscopy characterization with long-term immersion in the corrosive medium,indicating a long-term protection of magnesium alloy corrosion applications.