| Steel has been widely used in industrial production due to its good electrical conductivity,thermal conductivity,ductility,low preparation cost.However,steel suffers from serious corrosion since it is very active resulting in short service life and huge waste of resources.In order to improve the service life of steel,several effective methods have been developed including phosphating treatment and chromate treatment.However,the application of the above methods has been severely restricted as a result of high operation cost and also the threat they posed to the environment and human health.Therefore,new methods should be developed to solve the above problems.In recent years,inspired by the lotus leaf in nature,making use of simple environmental technology to prepare superhydrophobic materials to protect steel has potential application prospects.In this work,45#steel with superhydrophobic surface was constructed by different electrodeposition processes,magnetron sputtering of aluminum films and further modification of stearic acid.The relationship between the structure and wetting behavior of the composited coating,the corrosion resistance of the steel was systematically studied.The main contents are listed as follows:(1)A superhydrophobic composite coating was successfully prepared on the surface of 45#steel by a two-step process.The Zn coating was deposited on the surface of 45#steel sheet by direct current(DC)electrodeposition in a simple galvanized solution,and the micro/nano structure of the spherical particles of clusters on the steel was obtained by adjusting the electrodeposition time and current density.Then the composite coating with superhydrophobic surface was obtained by modification of stearic acid.The water contact angle of the coating was recorded.Scanning electron microscopy(SEM),X-ray diffraction(XRD)and Fourier transform infrared spectroscopy(FT-IR)were employed to investigate the morphology,structure and chemical composition of the coating.The corrosion resistance of the coating was evaluated by testing the polarization curve.The results showed that the water contact angle of the coating on the steel increased at first and then decreased with the increase of electrodeposition time and current density.When the current density is 6A/dm2 and the electrodeposition time is 20 min,the maximum water contact angle can reach 154.4°.In addition,the corrosion resistance of the 45#steel was significantly improved.(2)The PC(pulse current)electrodeposition technique was tried to obtain a more excellent granular micro/nano structure of the zinc deposits by adjusting the electrodeposition time,current density,pulse frequency and pulse duty cycle in a simple galvanized solution.A superhydrophobic composite coating was obtained by further modification of stearic acid.The water contact angle of the coating was recorded.Scanning electron microscopy(SEM)was employed to investigate the morphology of the coating.The experimental results showed that the PC electrodeposition process could improve the uniformity of the rough surface.With the increase of the electrodeposition time and the current density,the water contact angle of the coating on 45#steel surface increased first and then decreased.The influence of the pulse frequency and the pulse duty cycle on the water contact angle of the coating is not obvious.When the current density is 5 A/dm2.the electrodeposition time is 20 min,the maximum water contact angle can reach 155.6°.It can be concluded that the PC electrodeposition technology has no significant effect on the hydrophobicity of the coating compared with the DC electrodeposition.(3)In order to further improve the corrosion resistance of 45#steel,a layer of aluminum was deposited on the coating by magnetron sputtering.the optimal thickness of the aluminum film with uniform micro/nano structure of cluster spherical particles was obtained by adjusting the sputtering time,sputtering power and sputtering atmospheric pressure on the galvanized layer.The superhydrophobic composited coating on the steel was obtained by further modification of stearic acid.The water contact angle and roughness of the coating were tested.Scanning electron microscopy(SEM),X-ray diffraction(XRD)and Confocal Laser Scanning Microscope(CLSM)were employed to investigate the morphology and chemical composition of the coating.The corrosion resistance of the coating was evaluated by the polarization curves.The experimental results showed that the roughness of the zinc coating decreased with the increase of sputtering time and sputtering power,while the sputtering atmospheric pressure had no effect on the roughness of the coating.When the magnetron sputtering time is 20 min,the sputtering power is 300 W,the sputtering atmospheric pressure is 0.7 Pa,the aluminum film with suitable thickness obtained by the magnetron sputtering is superhydrophobic,which can further improve the corrosion resistance of the 45#steel. |
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