Synergistic Effect And Mechanism Of Zinc Salt Corrosion Inhibition

At present,the water injection system in oil field has a long injection life,which leads to the accumulation of corrosive substances in the equipment,and the pipeline and other equipment are seriously corroded.Although there are many types of corrosion inhibitors in the market,there is still a lack of corrosion inhibitor with strong universality and good corrosion inhibition performance.In this thesis,three new composite corrosion inhibitors such as ZGH,ZGEM and ZGPSM were developed based on the combination of zinc salt.The synergistic effect and mechanism of corrosion inhibition were studied.It has certain theoretical significance and practical value.The specific research contents were as follows:(1)The synergistic effect of zinc gluconate(ZnGL)and 2-hydroxyphosphonyl acetic acid(HPAA)on corrosion inhibition was studied by static weightlessness and electrochemical method.The results showed that:when ZnGL:HPAA=4:100(mg·L^-1)and the dosage was 100mg·L^-1,the corrosion inhibition rate reached 91.5%,and the composite inhibitor was named ZGH.ZGH was suitable for neutral and weak alkaline environment,and has good corrosion inhibition effect at 80?and salinity of 100000 mg·L^-1.At the same time,ZGH had a certain scale inhibition and good compatibility.Surface analysis,adsorption thermodynamics,electrochemistry and other characterization methods showed that ZGH was cathodic corrosion inhibitor,which can form a variety of protective films on the surface of carbon steel.The adsorption process was exothermic,spontaneous and entropy decreasing,and had obvious chemical-physical adsorption characteristics.(2)The synergistic effects of ZnGL,EDTMPS and MZLS were studied by single factor experiment and orthogonal design.The results showed that when ZnGL:EDTMPS:MZLS=6:80:30(mg·L^-1),and the dosage was 150 mg·L^-1,the corrosion inhibition rate reached 91.5%,and the composite inhibitor was named ZGEM.The factors influencing the corrosion inhibition effect of ZGEM were p H value,temperature and salinity in turn.ZGEM had good compatibility and better scale inhibition performance than ZGH.The results of various characterization methods showed that ZGEM is a mixed corrosion inhibitor and can form an adsorption protective film on the surface of carbon steel.The adsorption process was exothermic,spontaneous and entropy decreasing,and chemical adsorption is dominant.In addition,by optimizing the molecular structure of the inhibitor and calculating the frontier orbital energy,total molecular energy,global hardness and dipole distance,the relationship between the inhibition effect and molecular structure of ZnGL,HPAA,EDTMPS and MZLS was explored.(3)Sorbitol phosphate(SPA)was synthesized from sorbitol and phosphoric acid.The corrosion inhibition performance of SPA and its synergistic effect with ZnGL were studied by static weight loss method.Then they were mixed with sodium molybdate and PASP in quaternion.The maximum corrosion inhibition rate of ZnGL:SPA:Na Mo O₄:PASP=6:80:30:40(mg·L^-1)was 89.4%,named ZGPSM.At the same time,the effects of temperature,p H value and salinity on the corrosion inhibition performance were studied.The results showed that ZGPSM had good temperature and salt resistance under medium alkaline conditions.The results showed that SPA was a cathode type inhibitor and ZGPSM was a mixed inhibitor,which could form protective film on the surface of carbon steel,and had a good application prospect.