Synthesis Of 8-Hydroxyquinoline Derivatives And Its Corrosion Inhibition Study On Copper In 0.5M H₂SO₄ Solution

Copper is extensively investigated and used in industry,owing to its high electrical and thermal conductivities as well as excellent mechanical workability.Although its resistance is quite good in nearly neutral or slightly alkaline aqueous environment,copper is still vulnerable to corrosion in harsh condition.As corrosion of copper in seawater with high concentration of chlorine ions?Cl^-?is even more serious,copper anticorrosion in aqueous salt condition is a problem which needs to face up.Although there are many researchers report addressing copper inhibitors,which are dangerous to the environment and lack of economical applicability.In recent years,environmental requirements have become increasingly important,development of corrosion inhibitor of high efficiency and low toxicity for environmental protection has great prospects.Ionic liquid?IL?is a perfect choice to use as a corrosion inhibitor due to their exceptional properties of non-toxicity,excellent thermal stability,non-flammability,non-flammability and hydrophilic.In this study,four ionic liquids?ILs?with different carbon chain lengths based on8-Hydroxyquinoline were synthesized used as the corrosion inhibitions for copper in 0.5M sulfuric acid solution.The corrosion inhibition of copper has been explored systematically by electrochemical test,morphology analysis,quantum chemical study and MD simulations.Furthermore,the effect of various alky chain length on corrosion efficiency were investigated by theoretical calculations to explain the experimental results.The main work and innovation of this paper were as follows:1)Synthesis of target ionic liquids?ILs?The target products were synthesized through two different synthetic routes,using8-hydroxyquinoline as a substrate.The reactions involved in the two routes were the electrophilic substitution reaction on the benzene ring and the Williamson synthesis reaction of asymmetric ether.The difference of the two routes is that the different order of the benzyl group and the alkyl group introduced into the molecule.The results showed that firstly introduced the benzyl group by electrophilic substitution reaction and then introduced the alkyl group by Williamson asymmetric ether reaction can obtain a higher yield.At the same time,through the characterization of FT-IR?¹H-NMR spectra and mass spectrum can clearly indicated that the synthesized product is the desired target product.2)Study on corrosion inhibition of copper by the four studied ILs in 0.5 M H₂SO₄solutionThe data of potentiodynamic polarization curves and electrochemical impedance spectroscopy?EIS?indicate that:the copper surface has been protected in the present of the investigated ILs;with the addition of inhibitors,the corrosion current decreased obviously and the corrosion potential shows a significant move to negative,and the range of change exceeded 85 mv,indicating that the four ionic liquids were cathodic corrosion inhibitors in this corrosion system;besides,with the incremental alkyl chain length,inhibition efficiency rose firstly and then declined.Scanning electron microscopy?SEM?was used to analyze the surface morphology of copper and the results showed that the addition of corrosion inhibitors can effectively reduce the corrosion of the copper surface.By fitting several commonly used adsorption isotherms,it was found that the adsorption of the four ionic liquids on the copper surface conformed to the Langmiur adsorption model,and the standard adsorption Gibbs free energy is about-40 KJ/mol,indicating that the four kinds of ionic liquid inhibitors are mainly adsorbed on the surface of copper by chemical adsorption.Through quantum chemical calculations,some quantitative parameters of the four ionic liquid molecules were obtained and used to analyze the interaction and active adsorption sites between the molecules and copper surface.Finally,the adsorption model of corrosion inhibitor molecule on the copper surface was obtained through molecular simulation,which provided a theoretical support for the experimental results.