Study On Improvement Measures Of Cathodic Protection For Heavy Oil Pipeline

Because of the high density,the viscosity of heavy oil and anti poor liquidity,mostly adopt the method of heat transfer,in order to reduce heat loss,the outside pipeline are usually coated with anti-corrosion insulation,insulation of its complex structure can produce obvious for impressed current cathodic protection shield effect,the sacrificial anode material and cathode protection way put forward higher requirements.In this study,based on molecular dynamics and density functional theory simulation calculation method,combined with high-temperature electrochemical characteristics test,different aluminum alloy sacrificial anode materials were screened.Finally,through the design of sacrificial anode device and field application effect evaluation,the applicability of the sacrificial anode materials in corrosion protection of heavy oil pipeline was analyzed.The results showed that:among the five new Al-Zn-In sacrificial anodes with Ti,B and Ce alloying elements,the formation energy of 5#Al alloy sacrificial anodes with face-centered cubic cells(Al Zn Fe Si Cu Ti BCe)was relatively negative(-63.6257 e V/atom).The adsorption energies with H2O,H3O⁺,OH^-,CO₃^2-,HCO₃^-,Cl^-and SO₄^2-were 0.7792e V,3.9446e V,5.501e V,87.303e V,65.0270e V,4.4195e V and 7.9241e V,respectively.Under the simulated high temperature pipe transportation temperature(80?),the self-corrosion current density of 5#aluminum alloy sacrificial anode was the smallest(42.64?A/cm²),the current efficiency was as high as 89.41%,and there was no obvious local corrosion.Based on the polarization curve of the pipe material(TS/52K)and the corrosion rate test of the hanging pieces under different cathodic protection potential,the corrosion rate of the hanging pieces was lower than 0.01mm/a when-1.05V(SCE)cathodic protection potential was applied.Moreover,the working potential of 5#aluminum alloy sacrificial anode at 80?was less than the effective cathodic protection potential of-1.05V(SCE),and the corrosion rate of pipeline material decreased by 99.6%.An improved tile-type aluminum alloy sacrificial anode was designed,which can be installed in the patch position of the insulation pipe.The cathodic protection potential measured in the field was-1.033V(SCE,72?),and the protection effect was good.