| Because magnesium alloys have diverse excellent and unique physical,mechanical and processing properties,so magnesium alloys have broad application prospects in many industries that on behalf of automobile industry,aerospace and defense,3C products,biomedical materials and so forth.Unfortunately,there are two active electrons outside the nucleus of magnesium,and,magnesium and its alloys are easy to be oxidized and corroded by other corrosive medium,which impedes the application of magnesium alloy.Hence,protective measures are utilized to improve the corrosion resistance of magnesium alloys.With the rise of biomimetic materials industry,more and more researchers have found that superhydrophobic coating can greatly improve the corrosion resistance of metallic materials.In this study,As-cast AZ31 magnesium alloy is selected as the substrate,and the superhydrophobic surface of magnesium alloy is successfully prepared by combining laser scanning,surface modification of fluorosilane solution and heat treatment technology.The surface microscopic morphology is observed by FESEM,SEM and LSEM.The phase and composition are tested by XRD and XPS.The value of CAs and RAs are obtained by optical contact angle measuring instrument to study the static and dynamic wetting behavior of superhydrophobic surfaces.We discussed the effects of laser scanning parameters(power,frequency and rate),modification solutions,heat treatment time and temperature on the wetting performance.We also measured and discussed the anisotropic phenomenon,self-cleaning consequent and anti-icing properties of the superhydrophobic surface.Finally,we analyzed the actual application performance and corrosion resistance of the superhydrophobic surface.The main work content and conclusions are as follows:(1)In this essay,the rough structure of the surface is prepared directly by laser scanning technology.The influence of laser scanning parameters on the magnesium alloy surface morphology and the influence of modification process and heat treatment technology on superhydrophobic properties are explored.Combining the estimate of SEM image and LSEM figure,and different patterns(squares and strips),groove depth and width on the sample surface are controlled by adjusting the scanning parameters.The samples with best superhydrophobic property can be summarized as follows:the best scanning step size is 200?m,the best scanning rate is 100 mm/s,the best scanning frequency is 20 k Hz,and the best scanning power is25%(5 W).The optimum modified concentration of fluorosilane solution is 2 wt.%.The best heat treatment temperature and time are 150°C and 2 h,respectively.Combined with FESEM images and analysis shows that the as-prepared samples have a composite structure which is composed of micron level groove,submicron level mastoid and nanometer level particles.The CA value is as high as 159.8°and RA is as low as 2°.(2)The application performance of the superhydrophobic surface was studied.It was found that the samples prepared in this experiment show good superhydrophobic behavior to all kinds of water droplets that are often encountered in daily life.Because the air trapped on the superhydrophobic surface will form an air film,it exhibits an air cushion effect.It not only shows good superhydrophobic effect,but also excellent self-cleaning behavior,anti-ice and snow application performance.(3)This article also investigated the stability of superhydrophobic samples in various environments including acid,base,salts and air.It is found that the samples prepared in this paper can keep good stability in moderate strong acid,salt,alkali and air.The mechanical durability of superhydrophobic coatings is tested by the mechanical friction of sandpaper,the surface can also the hydrophobic performance to some extent.The adhesive tape is used to measure the adhesion strength of superhydrophobic samples,It maintains excellent superhydrophobic performance.(4)Finally,the corrosion resistance of the superhydrophobic surface was studied.The electrochemical test results show that the corrosion resistance of superhydrophobic surface was significantly improved in comparison to the untreated magnesium alloy substrate.According to the polarization curves of the two samples,the corrosion current density of PFOTES sample is reduced from 1.5×10-4A/cm2of substrate samples to 1.4×10-5A/cm2,the corrosion potential is increased from-1.67 V to-1.48 V.Because the smaller the corrosion current density,the slower the corrosion rate.The more positive the corrosion potential is,the more difficult it is to be corroded.Therefore,these data indicate that the superhydrophobic surface enhances the corrosion resistance of magnesium alloy.Electrochemical impedance spectroscopy(EIS)showed that the diameter of capacitive arc of PFOTES sample was much larger than that of substrate,and the impedance data also showed that the corrosion resistance of magnesium alloy was greatly improved by superhydrophobic surface. |
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