Corrosion Inhibition Performance Of Two Synthetic Quinoline Derivatives On Mild Steel And Copper In Acid Media

Quinoline derivatives have been attracted extensive attention in corrosion inhibitor research field owing to their low toxicity and N-containing heterocyclic structure for the past few years.However,low inhibition efficiency and bare toxicity research decelerate quinoline derivatives development.Hence,high-efficient and low-toxic inhibitors exploring is still a hot issue.In this thesis,two quinoline derivatives named 6-benzylquinoline?BQ?and 6-?quinolin-5-ylmethyl?benzene-1,2,3,4,5-pentasulfonic acid?QBPA?have been synthesized and characterized by ¹H NMR spectroscopy and Fourier transform infrared spectroscopy.Weight loss and electrochemical measurements were implemented to investigate the inhibition performance of BQ and QBPA on mild steel in 1 M HCl and copper in 0.5 M H₂SO₄,respcectively.Quantum chemical calculations and molecule dynamics?MD?simulation were implemented to explain the inhibition mechanism of these two organic molecules.The main work of this thesis are as follows:?1?The toxicity of typical inhibitors such as benzothiazoles,imidazoles,pyridines,schiff beses,sulfur-containing heterocyclic compounds and quinoline derivatives synthesized in this essay has been calculated by T.E.S.T software.The calculation found that only BQ and QBPA belong enviornmental friendly inhibitors because they own no health toxicity and low eco-toxicity among these inhibitors.?2?QB and BQPA acted as excellent inhibitors for mild steel in 1 M HCl solution and their inhibition efficiency enhanceed with the increase of concentration.The maximum inhibition efficiency was 96.54%for QB and 98.03%for BQPA?obtained from EIS at 298K?at 1 mM,respectively.The adsorption of QB and BQPA on steel surface obeyed Langmuir adsorption isotherm with a mixed physisorption and chemisorption mechanism.Electrochemical results indicated that QB and BQPA performed as both anode and cathodic type inhibitors without changing hydrogen evolution's mechanism.And the addition of inhibitors mainly hinders the active sites on steel surface.?3?QB and BQPA acted as excellent inhibitors for copper in 0.5 M H₂SO₄ solution and the maximum inhibition efficiency was 96.7%for QB and 98.3%for BQPA at 1 mM,respectively.Potentiodynamic polarization results indicated that QB and BQPA performed as cathodic type inhibitor and mainly impeded the diffusion process of oxygen.Electrochemical impedance spectroscopy showed that the addition of inhibitors mainly hindered the active sites on steel surface.And the adsorption of QB and BQPA on copper surface obeyed Langmuir adsorption isotherm with chemisorption mechanism.?4?Results of all testing methods showed that QBPA owned a better inhibition performance than BQ.It could be explained by Quantum chemical calculations results.HOMO and LOMO of BQ were almost localized evenly on the quinoline ring and benzyl group?linked to quinoline ring?.By contrast,HOMO of QBPA was distributed in quinoline ring while its LUMO was located in the rest of molecule structure.Hence,rational assumption can be proposed that QBPA includes more adsorption sites than BQ,issuing in a stronger adsorption capability.