Research On Synthesis And Performance Of Gemini Imidazoline Corrosion Inhibitors

Nowdays metal corrosion will not only cause economic losses but also destroy the ecological environment,so adding corrosion inhibitors to inhibit metal corrosion is a long-term effective and low-cost measures.The imidazoline inhibitor is used widely,the imidazolium quaternary ammonium salt inhibitor which formed by its quaternization has a stable conformation,low toxicity and no irritation.Therefore,in this paper,the imidazoline Gemini surfactants was employed as corrosion inhibitors instead of the traditional single-chain surfactants,and corrosion inhibition effects of imidazoline Gemini surfactants are studied in different corrosive media.In this paper,a series of imidazoline Gemini surfactants with different hydrophobic chains and different chain lengths were synthesized.Using lauric acid(or oleic acid),diethylenetriamine as materials,xylene as a water-carrying agent,the imidazoline intermediates was synthesized at high temperature by intermolecular and intramolecular dehydration.And then it was quaternized with dimethyl carbonate to form imidazoline quaternary ammonium salt.Finally it reacted with dibromoethane to obtain the corresponding cationic imidazoline Gemini surfactants.It was recrystallized with acetone repeatedly to obtain the target product,which were named lauryl imidazoline Gemini surfactant LI(Lauryl Imidazoline)series and oleic acid imidazoline Gemini surfactant OI(Oleic acid Imidazoline)series.The structures of the target products were characterized by Fourier transform infrared spectrometer(FT-IR)and nuclear magnetic resonance hydrogen spectrum(1H NMR),elemental analysis and X-ray photoelectron spectroscopy(XPS).The physical and chemical properties of the aqueous solution were investigated by surface tension,foaming properties,emulsifying properties and solubility.Finally,effects of the concentration of imidazoline Gemini surfactant and temperature on the corrosion of metal Q235 sheet werestudied by static weight loss method.The corrosion inhibition of imazoline Gemini surfactants in different corrosive media(salt solution,hydrochloric acid,high calcium solution)and its adsorption mechanism on the surface of metallic materials were studied by electrochemical method.The results showed that imidazoline Gemini surfactants had higher surface activity compared with the traditional surfactants,the critical micelle concentration of it was lower 2~3orders of magnitude than that of traditional surfactants,and its surface tension could reach 22.613 mN/m.Furthermore it had good emulsifying properties and foaming properties,and was soluble in polar organic solvents.In the static weight loss test,these six imidazoline Gemini surfactants had better corrosion inhibition effect on Q235 steel when the mass fraction of salt solution was 3.5%,and the corrosion inhibition rate can reach more than 90%.When the corrosion temperature was different,the uniform corrosion rate of the six imidazoline Gemini surfactants was increased with the temperature rise,while the corrosion inhibition rate was decreased.When the temperature was 30 ?,the corrosion rate reached the maximum.The results of polarization curves showed that corrosion current density was decreased and the corrosion potential moved to forward direction in the systems with the addition of imidazoline Gemini surfactants solution,compared with the non-added blank control group.And in the salt water medium,it was the anode electrode inhibition of mixed corrosion inhibitor.It belonged to the mixed control type corrosion inhibitor in the medium of 1 mol/L hydrochloric acid solution.It was the anode electrode inhibition of mixed corrosion inhibitor in the high calcium solution.In the EIS impedance spectroscopy study,the Nyquist diagram was an approximately semicircular single-element arcing and was consistent with the conclusion of the electrochemical polarization curve in different corrosive media,when corrosion inhibitor was not added or added in different corrosive media.The results of adsorption thermodynamics showed that the behavior of these corrosion inhibitors on the surface of Q235 steel was in accordance with the Langmuir adsorption.The free energy of the adsorption process was bellow zero(?G < O)which indicated that the adsorption reaction of the corrosion inhibitor on the steel was spontaneous.The results of adsorption kinetics showed that the relation of the corrosion rate and temperature was in agreement with the Arrheniusformula.The addition of imidazoline Gemini surfactants increased the activation energy of the reaction system,which slowed down the corrosion.