Wall sticking inhibition of high water cut crude oil (below pour point) by underwater superoleophobic PA-FC modification

Abstract To inhibit wall sticking during gathering of high water cut crude oil, based on the deposition characteristics of the complexes by reaction of phytic acid (PA) with ferric chloride (FC), a simple and environmentally friendly method for carbon steel plate modification was adopted in this study. The effects of reaction time, FC concentration, and deposition times on surface wettability and morphology were investigated. It appeared in the results that the wettability of the surface no longer changed after 1 min of reaction. After two times of deposition, the carbon steel exhibited superhydrophilicity in air and superoleophobicity under water, and more pronounced nano-structures were observed. Comparing with similar works, no electroplating, heating and other devices are required during the entire coating process. Moreover, for the sake of clearly explaining the mechanism of wettability conversion during PA-FC modification, the theory of surface energy and adhesion work were used to quantitatively calculate the adhesion strength of oil droplet on solid surfaces. It was found that the hydrophilization and underwater oleophobicization of materials were essentially a process of increasing the polar component of surface energies, and the opposite adhesion state of oil in air and under water was demonstrated theoretically. Finally, the anti-sticking ability at low temperatures of treated carbon steel was evaluated experimentally. The PA-FC coating showed good oil gel prevention performance below the pour point of crude oil. In conclusion, the wall sticking prevention method proposed in our work provides another way for flow assurance of the transportation of high water cut crude oil.