Research On Anticorrosion Mechanism Of Solid Corrosion Inhibitor For Buried Thermal Insulation Pipeline

Due to the complex structural characteristics of buried steel insulation pipelines,once water enters,it may cause serious electrochemical corrosion of the pipeline.The addition of solid corrosion inhibitors is a more effective corrosion inhibitor for buried steel insulation pipelines.Anti-corrosion technology.The research in this paper is based on the Discover module and DMol3 module of Material Studio software,and is used for sodium gluconate(C₆H₁₁Na O₇),ethylene diamine tetra(methylene phosphonic acid)Sodium(C₆H₁₂O₁₂N₂P₄Na₈C),sodium lauroyl sarcosine(C₁₅H₂₈NO₃Na),ethylenediamine tetraacetic acid disodium(C₁₀H₁₄N₂Na₂O₈)four different corrosion inhibitor molecules have been simulated and theoretically screened;Prepare the selected corrosion inhibitors into solid corrosion inhibitors by high temperature melting method,and the release rate test of the solid corrosion inhibitor and the evaluation of the corrosion inhibitor effect are combined.Linear polarization,potential polarization and alternating current impedance spectroscopy(EIS)and other electrochemical tests and analysis,to discuss its corrosion inhibition mechanism and applicability in the protection of high-temperature transmission pipelines.The research results show that in the molecular dynamics simulation experiments of the four corrosion inhibitor molecules in the aqueous system and the vacuum system,the adsorption energy of the ethylene diamine tetra(methylene phosphonic acid)Sodium molecule on the Fe surface is the maximum,which is-2850.95 respectively.k J·mol^-1,-544.65 k J·mol^-1;In quantum chemistry calculations,among the four corrosion inhibitor molecules,the highest occupied orbital energy E_HOMOof the ethylene diamine tetra(methylene phosphonic acid)Sodium molecule is the largest and the energy gap difference?E is the smallest,which are-2.044 e V and 0.926 e V,respectively;the softness of the corrosion inhibitor molecule is the largest,2.160e V^-1.Analysis of the results of comprehensive molecular dynamics and quantum chemistry calculations,ethylene diamine tetra(methylene phosphonic acid)Sodium molecule should have the best corrosion inhibition performance.The release time of the prepared solid corrosion inhibitor under pipeline transportation conditions is 33 d.When the dosage of solid corrosion inhibitor is 5000 mg/L,the corrosion inhibition efficiency is 89.16%.After adding the solid corrosion inhibitor,the polarization resistance R_pof T/S-52K steel increases rapidly,the electrode reaction resistance increases,the self-corrosion potential is significantly positively shifted,the corrosion rate is significantly reduced;The effective components of the solid corrosion inhibitor can form an adsorption film on the surface of the metal,retard the anodic reaction process of corrosion electrochemistry,and play a corrosion inhibition effect.With the extension of the corrosion time,the film resistance R_mof the adsorption film of the corrosion inhibitor increases significantly.