Preparation And Functional Properties Of Superhydrophobic Surfaces On X90 Pipeline Steel

With the increasingly stringent requirements to energy pipeline transportation by the social development,X90 pipeline steel,which has high resistance to deformation and low yield ratio,is expected to be the next generation of high tensile and large diameter industrial application steel.However,most of the pipeline steels are corroded easily,furthermore there exists also adhesion resistance in liquid delivery pipeline,so its application effect is seriously affected.Copper has good corrosion resistance,and it can be used as ideal anticorrosion coating for pipeline steel.The superhydrophobic surface not only has the ability of anti-adhesion to reduce the liquid conveying resistance,but also has the function of inhibiting corrosion.Therefore,the above problems can be solved by preparing superhydrophobic surface on X90 pipeline steel substrate coated with copper protection layer.However,at present due to the limitations such as severe experimental conditions,high cost,and poor stability especially poor mechanical stability,the superhydrophobic surface is not used as widely as we expected.Therefore,it is of great significance to carry out research work in this field.In this paper,the Cu protective layer on X90 pipeline steel substrate was prepared through the electrodeposition treatment,and then the superhydrophobic surface was obtained by the hydrothermal reaction and the modification with perfluorooctanoic solution.This method does not require complex equipment,and the preparation process is simple and inexpensive.The influence of main experimental parameters on the sample surface wettability: the main salt concentration of hydrothermal reaction,the hydrothermal reaction time,the hydrothermal reaction temperature,and the immersion time of perfluorooctanoic solution was studied by single factor variable method,and the best preparation technology was determined.The contact angle of water on the final sample surface was 161.24° and the rolling angle was about 3°,the superhydrophobic surface was obtained.The microscopic morphology was observed by scanning electron microscopy,the results showed that the micro scale flower like structure composed by nano scale petal like structure was formed on the superhydrophobic surface.This kind of multi-scale structure could prevent water droplet intrusion,so that it was difficult for the surface to be wetted,and the gas interception rate between the water droplet and the structure was 95.1% calculated by Cassie equation.The 3D morphology showed that the micro nano structure increased the surface roughness,at the same time,minimized the absolute value of the skewness.The fractal dimension confirmed quantitatively that the micro/nano structure increased the multi-scale property of the surface.The chemical composition of the superhydrophobic surface was studied by X ray energy spectrum and Fourier transform infrared spectroscopy,and it was obvious that the low energy modifier was successfully grafted onto the surface,together with the function of micro/nano hybrid rough structure and the superhydrophobic surface was obtained.Meanwhile,the functional characteristics of the superhydrophobic surface were studied.The superhydrophobic surface showed lyophobicity to the other liquids with different surface tension and even oil except for water droplet.The surface had outstanding anti-adhesion performance with no external force or other factors and gave expression to good self cleaning just like “lotus effect”.When an external force acted on water droplet,the wettability of surface changed from stable Cassie state to Cassie impregnation state,and adhesion rose.Based on the model,the transformation mechanism of the wetting pattern was described.The stability of the superhydrophobic surface was studied,and the contact angle and rolling angle were almost unchanged at 6 months,which indicated that the surface hydrophobicity was long-term stability.The thermal stability test testified that the surface could remain superhydrophobic under 200°C,when the temperature was higher than 250°C,the surface transformed into superhydrophilic due to the thermal decomposition of low energy modifier.The mechanical abrasion experiments showed that after 800 mm abrasion the surface still maintained superhydrophobic,and it indicated the surface had good mechanical stability.The wettability of superhydrophobic surface was in response to the pH value of the solution,it was found that the strong acid solution would destroy the surface morphology and strong alkali solution destroyed both the morphology and chemical composition of surface,so the surface was not suitable for alkali environment.The electrochemical test results showed that the corrosion potential of the superhydrophobic surface increased an order of magnitude,and the corrosion current density decreased two orders of magnitude as compared to X90 steel substrate.Meanwhile,the capacitance arc radius of the superhydrophobic surface was also far larger than X90 steel substrate.These demonstrated that the prepared superhydrophobic surface possessed good corrosion resistance,and the corrosion mechanism was explained by the fitting circuit.