| The acid medium used in oil well acidification stimulation techniques would severely erode downhole oil well pipes and metal equipment and cause security problems and economic losses.In the present,the research on corrosion inhibitors used for high temperature conditions are relatively little at home and abroad and with some deficiencies such as unperfectly inhibition effect,easily precipitating and forming coke,with pollution of the environment ground and poor compatibility,et al.Mannich base corrosion inhibitors is one of the main research topics of acid corrosion inhibitors for high temperature with good inhibition performance,the resistance of high temperature and high concentrations of acid,as well as good compatibility,et al.In this paper,we designed and synthesized two different structures of Mannich base high-temperature acidizing corrosion inhibitors based on the inhibition mechanism of Mannich bases corrosion inhibitor.The raw materials are the cinnamic aldehyde,ketone with phenyl(acetophenone and benzylidene acetone),formaldehyde and amine(polyamine and primary amine with six-membered ring).We optimized the synthesis process by single factor analysis method,finally screened out the optimal synthesis conditions of M-4A multi-Mannich bases acid corrosion inhibitor is n(cinnamaldehyde):n(diethylenetriamine):n(acetophenone):n(formalin)is 1.1:1.0:2.1:1.2,ethanol as solvent and the added amount is 1/3 of the total mass of reactants,pH value of reaction is 9,the synthesis temperature is 80 ? and the synthesis time is 6h;The optimal synthesis conditions of M-CPH single-Mannich base acid corrosion inhibitor is n(cinnamic aldehyde):n(Benzalacetone):n(cyclohexylamine)is 1.1 1 1.0:1.2,1,4-dioxane as solvent,pH value of reaction is 6,the synthesis temperature is 70 ? and the synthesis time is 6h,the structural characterization results of M-4A and M-CPH consistent with the expectations.We studied the inhibition performance of M-4A and M-CPH in different corrosive environments,the results shown that the resistance of temperature of the two Mannich base inhibitors can reach up to 140? in 20%hydrochloric acid solution,and inhibition effect reached the A level of standard of the oil and gas industry.Through the respectively study of them complexed with synergist(KI and CuBr)shown that,the synergy between M-4A and KI,CuBr was both good and the inhibition performance of M-4A was significantly improved after complexed with synergist;M-CPH only has a good synergy with KI.The inhibition performance of M-4A complexed with M-CPH is better than that of any one corrosion inhibitor's alone used,The inhibition performance of their optimal complexed corrosion inhibitor M-AC-1 complexed with KI,CuBr is also enhanced.From the electrochemical study shown that M-4A and M-CPH respectively belongs to mixed-type corrosion inhibitor of in the main inhibiting the cathodic reaction and in the main inhibiting the anode reaction,both of them can inhibit the cathodic hydrogen evolution reaction and the anode metal corrosion reaction.From the study of SEM,EDS and the mechanism of adsorption and forming membrane shown that the molecules of M-4A and M-CPH corrosion inhibitor were absorbed on the metal surface by the found with the metal surface,forming a hydrophobic protective film on the metal surface to hinder the contacts of corrosive medium and metal surface,and thus play a role of inhibiting the metals corrosed.The adsorption of M-4A and M-CPH on A3 steel surface in hydrochloric acid medium meet with Langmiur adsorption isotherm model and the process was spontaneously and exothermic.The adsorption of M-4A on A3 steel surface was a mixed-type absorbtion of physical and chemisorption with entropy reducing;while M-CPH was a chemisorption with entropy increasing. |
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