Wettability effect of coatings on drag reduction and paraffin deposition prevention in oil

Several techniques have been used to minimize the problems caused by paraffin deposition, and internal coating is considered an attractive technological alternative. In this work, the influence of the eight coatings, such as polyvinylidene fluoride (PVDF), silicone rubber, methyl acrylate-stytene copolymer (MAS), polyurethane (PU), epoxy resin (EP), on drag reduction and paraffin deposition prevention is evaluated by rotation viscometer and cold spot. The wettability characteristics, the advancing and receding contact angles between coating surface and ozocerite or crude oil were measured by the Wilhelmy plate method. A correlation between both results was also obtained. According to the dynamic contact angle and the hysteresis factor of the resin coatings against asphalt, ozocerite and crude oil, the properties of drag reduction and paraffin deposition prevention on coatings were briefly discussed. The wetting characteristics of the surface have a significant influence on the amount of paraffin deposited and shear force. The low surface energy of fluoroethylene polymer, silicone rubber and methyl acrylate-stytene copolymer coatings, which have obvious effect on drag reduction and paraffin deposition prevention, can increase the advancing contact angle and hysteresis factor and decrease the steel surface wettability against asphalt, ozocerite or crude oil. The great hysteresis factors of coatings against asphalt, ozocerite or crude oil may have an important effect on the inhibition of paraffin deposition and drag reduction in crude oil.