Experimental and Theoretical Analysis of Quinoline Diquaternary Ammonium Salt as Corrosion Inhibitor

Two water-soluble bisquinoline quaternary ammonium salts with hydrophobic structures(BQA-1 and BQA-2) were prepared from quinoline, alpha'-dichloro-p-xylene and cis-1,4-dichloro-2-butene. The corrosion inhibitory property of BQA-1 and BQA-2 on Q235 steel in 1 mol/L hydrochloric acid solution and their adsorption behavior on Q235 steel surface were studied by means of mass loss measurement, electrochemical technique, scanning electron microscopy (SEM) and quantum chemical calculation. The mass loss results show that BQA-1 and BQA-2 had good corrosion inhibition effect on carbon steel in hydrochloric acid, when the mass concentration was O. 5 g/L and the temperature was 30 C, the inhibition efficiencies of BQA-1 and BQA-2 were both over 94. 59%. In addition, the temperature rise resulted in a faster rate of desorption of BQA-2 than BQA-1. Electrochemical experiment results show that BQA-1 and BQA-2 are mixed type inhibitor and preferentially inhibited the cathodic reaction. Thermodynamic and activation energy parameters show that the adsorption of BQA-1 and BQA-2 on steel surface is spontaneous and exothermic, conforming to the Langmuir' s adsorption isotherm and mainly based on chemical adsorption. Quantum chemical calculation results show that the active sites of BQA-1 and BQA-2 are concentrated on the quinoline rings and heteroatom, and the ability of BQA-1 and BQA-2 molecules to accept electrons is greater than the ability to provide electrons.