Investigations Of Imidazole Derivatives As Corrosion Inhibitors On Copper In 0.5M H₂SO₄ Medium

Copper metal is relatively rich in natural resources,low in production cost,and has good thermal conductivity,electrical conductivity,ductility and mechanical processing.Therefore,it is widely used in various fields of the national economy and is an indispensable important metal material for the national economy.However,copper metal and its alloys are easily corroded in the environment,causing damage,failure or shortened life of related equipment or devices,which may lead to serious economic losses or major accidents.For this reason,the corrosion protection of metallic copper has attracted extensive attention and research.Among them,the corrosion inhibitor technology has the advantages of economy,strong operability,simple equipment,and has good application prospects in the field of metal anti-corrosion.Imidazole compounds are one of the important azole derivatives.They are widely used as antibacterial agents,anti-inflammatory drugs and insecticides.Because of their wide sources,easy dissolution in water,environmental protection,and eco-friendly characteristics,they are considered to be a class of environmental protection and environmentally friendly corrosion inhibitors of copper.Studies have shown that imidazoles such as imidazole,4-methyl-5-hydroxymethylimidazole,1-phenyl-4-methylimidazole,2-mercapto-1-methylimidazole have significantly slowed down the corrosion of copper.However,the relationship between the type and number of imidazole ring substituent and corrosion inhibition are insufficiently studied.Therefore,in-depth study of related content has practical and theoretical guiding significance for the selection and synthesis of corrosion inhibitors.In this paper,four imidazole derivatives were selected as corrosion inhibitors,they were levamisole(LMS),4-phenylimidazole(PIZ),3-bromo-6-chloro imidazole-pyridazine(BCIP),and 6-chloro imidazole-pyridazine(CIP),the corrosion inhibition performance of LMS,PIZ,BCIP,and CIP in 0.5 M H₂SO₄ solution for copper was investigated by a combination of experimental tests and theoretical calculations.In the experiment,the electrochemical parameter characterization method,surface composition analysis method and intuitive morphological analysis method were used to study the relationship between the concentration of corrosion inhibitor and corrosion inhibition efficiency,the mechanism of corrosion inhibition was analyzed,then the simulation calculation technology was used to obtain the quantum chemical parameters of four molecules,analyzed the relationship between these parameters and the corrosion inhibition performance.The main results obtained are as follows:(1)The electrochemical impedance spectroscopy and potentiodynamic polarization curves indicated that all four imidazole derivatives can delay the corrosion of copper,and the corrosion inhibition efficiency increased with the concentration of the corrosion inhibitor augments.However,under the same corrosion inhibitor concentration,the corrosion inhibition effect was different.Among them,at a concentration of 8.0 mM,the corrosion inhibition efficiency of LMS was 99.03%,and that of PIZ was 95.84%;at a concentration of 5.0 mM,the corrosion inhibition efficiency of BCIP was 93.63%,and that of CIP was 84.33%.The relationship of the efficiency of four corrosion inhibitors was:LMS>PIZ,BCIP>CIP.(2)The analysis results of the electrochemical experiment parameters showed that the corrosion inhibition mechanism of the four imidazole derivatives on copper was not the same.Among them,LMS was a cathodic corrosion inhibitor,and PIZ,BCIP,and CIP were mixed-inhibition corrosion inhibitors;the adsorption of four imidazole derivatives on the copper surface conformed to the Langmuir adsorption model,and absolute values of(35)G⁰_ads was between 20 KJ/mol and 40 KJ/mol,which was the contribution of both the physisorption and chemisorption.(3)Atomic force microscopy and scanning electron microscopy analysis results suggested that the corrosion inhibitors significantly improve the flatness and smoothness of the copper surface.The roughness of the copper surface after adding LMS,PIZ,BCIP,and CIP were 11.4 nm,24.5 nm,31.1 nm,and 38.1 nm,respectively,its surface roughness was far less than 72.7 nm without corrosion inhibitor,confirming that the corrosion inhibition of four imidazole derivatives on copper was objective and remarkable.(4)X-ray photoelectron spectroscopy analysis results revealed that four imidazole derivatives form coordination bonds with copper atoms on the surface,which confirmed the chemical adsorption between the corrosion inhibitor and the copper atom.(5)Quantum chemical calculations showed that the energy difference of the frontal orbit of LMS was smaller than PIZ,the that of BCIP was smaller than CIP,the dipole moment of LMS was larger than PIZ,and that of BCIP was larger than CIP,which was theoretically explained that LMS and BCIP were more likely to adsorb and form chemical bonds on the copper surface.The adsorption binding energy of the inhibitor molecules obtained by molecular dynamics simulation on the Cu(111)crystal plane showed that the binding energy of LMS was 346.5 KJ/mol greater than 293.6 KJ/mol of PIZ,and that of BCIP was 237.4 KJ/mol greater than 196.0 KJ/mol of CIP.It was theoretically explained that all four corrosion inhibitors can effectively combine with copper,but LMS and BCIP were more closely combined,and the ability to block the corrosion medium from being in touch with copper was stronger,and the corrosion inhibition performance of LMS was better than PIZ,and that of BCIP was better than CIP.Therefore,to a certain extent,the calculation of quantum chemical parameters can provide guidance for the selection and synthesis of corrosion inhibitors.(6)All test results suggested that the corrosion inhibitory efficiency was related to the number of heteroatoms.When there were more heteroatoms in the inhibitor molecules,more adsorption sites can be provided,resulting in an increase in the corrosion inhibitory efficiency.