| Addition of corrosion inhibitor was a high-efficiency method to inhibit metal corrosion.In this paper,two types of anti-oxygen corrosion inhibitors were synthesized for the oxygen corrosion problem of gas injection wells in the field of nitrogen injection oil recovery,and the inhibition performance was evaluated in high salinity formation water corrosion medium.Cyanuric chloride was used as the parent and reacted with pyridine and iminodiacetic acid,two inhibitors containing s-triazine rings were synthesized,which were referred to as TCT-1 and TCT-2 respectively;lauric acid,oleic acid,and stearic acid were used as raw materials,reacted with 3-dimethylaminopropylamine to obtain amide intermediates.The intermediates were reacted with 4-chloromethylpyridine to prepare three quaternary ammonium salt corrosion inhibitors with hydrophobic chains,which were referred to as B-1,B-2,B-3 respectively.The dissolution and dispersion experiments showed that the inhibitor B-3 was poorly soluble and dispersible in corrosive media,the other four inhibitors showed good dissolvability and dispersibility.Using static weight loss method,the anti-oxygen corrosion effect of corrosion inhibitors with good solubility for P110 steel was investigated in high salinity simulated formation water corrosive medium at 90?,continuous introduction of oxygen,and the inhibitor was evaluated in terms of the inhibitor concentration,temperature,Ca2+concentration and Cl-concentration.The experimental results showed that these four corrosion inhibitors had certain effects of inhibiting oxygen corrosion.The prepared corrosion inhibitors were separately compounded with sodium molybdate and the compounded corrosion inhibitors were superior to the single component corrosion inhibitors.TCT-2 compounding effect was superior to TCT-1,and B-2 compounding effect was excellent than B-1.TCT-2,B-2 and sodium molybdate were compounded and the corrosion inhibitor performance was further improved after compounding.The optimal compounding concentration was:300 ppm TCT-2+300 ppm B-2+100 ppm sodium molybdate(named MUTB corrosion inhibitor),the inhibition rate reached 92.5%under the static corrosion conditions.Combined with the high temperature and high pressure dynamic corrosion evalution method,the evaluation of compound corrosion inhibitor was conducted from six aspects of oxygen partial pressure,temperature,Ca2+ concentration,Cl-concentration,flow rate,and pre-filming time.The mechanism of corrosion inhibitor was studied through potentiodynamic polarization curve test,scanning electron microscope,electron spectroscopy and corrosion inhibitor molecular structure.The polarization curve study showed that TCT-2 and B-2 were composite inhibitors based on suppression of cathode corrosion,B-1 and TCT-1 were cathode corrosion inhibitors,and MUTB was composite inhibitor.The energy spectrum analysis showed that the content of Mo and N elements on the surface of carbon steel increased,and the decrease of Fe element content was less than that of the blank group.MUTB formed a good protective film on the surface of carbon steel.The structural analysis showed that the corrosion inhibitor formed a coordination bond with the empty orbit of Fe atoms through N,O,heterocyclic and other polar groups,and then formed a stable chemical adsorption on the surface of the carbon steel.N+ions can form physical adsorption through the electrostatic force.on the surface of carbon steel,and sodium molybdate is passivated on the surface of carbon steel to form insoluble Fe-MoO4-Fe2O3 protective film.In addition,the carboxyl groups in TCT-2 can also be complexed with the metal ions Fe3+ and Ca2+to form a protective film.The double bonds in the B-2 hydrophobic chain can form an arched hydrophobic film on the metal surface and increase the coverage area of the film. |
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