| Most loose oil layers have sanding in the production process.Sanding will cause erosion of underground equipment and wear of ground equipment,and reduce the production of oil and gas wells.Therefore,oil and gas wells that possibly sanding during production requires sand control.In oil exploitation,the gap of the sand control screen was often blocked due to the adhesion of additives such as polyacrylamide(PAM),which seriously reduces the productivity of the oil well and affects the normal production.At the same time,because the sand control screen is in high temperature and high pressure for a long time,and soaking in multiphase fluids including many corrosive media,which lead to corrosion and damage.The superhydrophobic surface not only has low adhesion,which reduces the adsorption of additives such as polyacrylamide by the sand control screen,but also has good corrosion resistance.Therefore,the superhydrophobic surface can be constructed on the sand control screen to achieve low adhesion and corrosion resistance.At present,most of the sand control screens are made of stainless steel,in this paper,combined with the service environment of sand control screen,316L stainless steel is taken as the research object to explore the feasibility of superhydrophobicity on the surface of the screen.In this paper,the superhydrophobic coatings were prepared by anodic oxidation and electrodeposition on 316L stainless steel surface.The influence of the main experimental parameters on the surface wettability of the two preparation schemes was studied by single factor variable method.The test was optimized and the superhydrophobic coatings prepared by two test were compared to determine to build the roughness structure on 316L stainless steel surface by electrodeposition.The static contact angle between the sample surface after low energy modification and the water droplets was 160.46°,and the rolling angle was 8.3°,showing superhydrophobicity.The surface microstructure of electrodeposited sample was micron-scale prismatic protrusion and nano-scale pyramidal convex structure by SEM,but the specular reflection of the coatings was uneven,and the air film was defective.In order to improve the uniformity of the electrodeposited nickel coating,0.3 mol/L Cu2+was added to the electrolyte to form a leaf-like composite structure by micro-scale dendritic and nano-scale dendritic composition under electrodeposition conditions.The static contact angle with the water droplet after low energy modification is161.27°,and the rolling angle is 7.8°.The solid-liquid actual contact area between electrodeposited nickel sample and the water droplet is 4.0%,and actual contact area between copper-nickel co-deposition sample and the water droplet is 3.2%.Copper-nickel co-deposition has greater roughness and more evenly distributed height difference than single electrodeposited nickel surface,and the skew value is closer to0,which improve the multi-scale surface of sample.The chemical composition of the electrodeposited nickel and copper-nickel co-deposited samples was analyzed by X ray energy spectrum and fourier transform infrared spectroscopy.The results showed that the tetradecanoic acid was successfully grafted onto the surface of sample by immersion,which played a role of low energy modification and make wettability transformed from superhydrophilic to superhydrophobic.At the same time,the related properties of the surface of electrodeposited nickel and copper-nickel co-deposited samples were studied.When there is no external force,the surface of electrodeposited nickel and copper-nickel co-deposited samples has great low adhesion,and when external force exists,the wetting state between the contact interfaces changes from Cassie state to Cassie infiltration state,which result in a little adhesion force,and the Cassie state is restored after removing the external force,indicating adhesion force is lower.Superhydrophobic sample surface can reduce the adsorption of PAM on it,among which electrodeposited nickel sample has advantages in reducing PAM adsorption.After the natural placement for 6 months,the wettability of the electrodeposited nickel and copper-nickel co-deposited samples was almost constant,showing it is long-term stable.Under strong acid conditions,the microstructure of sample surface slightly changed,but the micro-nano composite structure still exists and maintains superhydrophobicity.Under strong alkali conditions,the solution reacts with the low energy modifier,resulting in an increase in surface free energy,and the surface changes from superhydrophobic to hydrophilic.The contact angle and mass of the surface of electrodeposited nickel sample during the erosion were smaller than those of the copper-nickel co-deposited sample,indicating that the surface of electrodeposited nickel sample was more resistant to erosion.It is found that when the superhydrophobic surface is kept above 250°C,the tetradecanoic acid will be thermally decomposed,which result in an increase in surface free energy and loss of superhydrophobicity.However,when the temperature is maintained at 200°C for 15 h,the surface of sample still has superhydrophobicity,indicating that the prepared sample work at about 200°C and has a certain high temperature resistance.The corrosion potential of stainless steel substrate is-0.2245 V,the corrosion potential of surface of electrodeposited nickel sample is-0.1484 V,and the corrosion potential of surface of copper-nickel co-deposited sample is-0.0484 V.The corrosion potential of the copper-nickel co-deposited sample is the highest,causing that the corrosion tendency is minimal;the self-corrosion current density of copper-nickel co-deposited sample is 6.9232×10-9A/cm2,it is much smaller than that of electrodeposited nickel sample is 1.5054×10-8A/cm2 and stainless steel substrate is6.9116×10-7A/cm2,indicating that the copper-nickel co-deposited sample has a lower corrosion rate;the copper-nickel co-deposited sample has a much larger radius of capacitive arc than the electrodeposited nickel sample and stainless steel.Therefore,the copper-nickel co-deposited sample has better corrosion resistance. |
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