Benzimidazole And Its Derivatives As Corrosion Inhibitors For Mild Steel In H₂SO₄ Solution

Q235 steel is a kind of metal materials used widely in modern industry, and the effect of inhibitors on the corrosion process of the corrosion behavior of Q235 steel in the acidic medium, can provide the theoretical basis for the practical application feasibility of screening inhibitor. With the requirement of environment protection to improve development efficiency, the research and development of high efficiency, environmentally friendly corrosion inhibitor has become an important topic in the study of corrosion inhibition.Benzimidazole compounds as common pickling inhibitor has the advantages of low toxicity, high efficiency, and easy degradation. This paper selected four kinds of different substituents of Benzimidazole corrosion inhibitor, influenced by electrochemical measurement, weight loss test, and surface morphology analysis and quantum chemistry calculation analysis method to study the four kinds of material corrosion of Q235 steel in 0.1M H2SO4 solution. There were four kinds of corrosion inhibitors were Benzimidazole, 2-Aminobenzimidazole, 2-Phenylbenzimidazole, omeprazole, they have good thermal stability, low toxicity, no smell, and the structure of unsaturated functional groups, and key ring containing N, S atoms. Benzimidazole derivatives with different substituents on the metal surface with different adsorption capacity, therefore, we can replace the base to improve the corrosion resistance of compounds by selecting the appropriate. In this thesis, the main research results are as follows:(1) The test results showed that the AC impedance test, the charge transfer resistance Rct increases with the concentration of corrosion inhibitor, the inhibition efficiency increased gradually, while the electrical double layer capacitor Cdl decreases, this is because the dielectric constant is smaller and larger volume of corrosion inhibitor molecules adsorbed on the substitution water molecules on carbon steel surface, and a layer of adsorbed film on the carbon steel surface, can effectively prevent the corrosion of carbon steel in sulfuric acid. The test results of polarization curves showed that, with the addition of corrosion inhibitor, the corrosion current density of Icorr decreased significantly, indicating that the corrosion inhibitor is added in the medium of sulfuric acid can effectively inhibit Q235 steel. The electrochemical test results consistent with the weight loss test.(2) Benzimidazole corrosion inhibitor adsorption type corrosion inhibitor, coverage is an important parameter of the theta adsorption behavior. In the 298 K, four kinds of organic corrosion inhibitor adsorption on the surface of Q235 steel were subjected to Langmuir adsorption model. According to the Gibbs free energy of adsorption process of G ads, can judge the corrosion inhibitor molecules adsorbed on the surface of carbon steel was a spontaneous process, and the adsorption process and adsorption.(3) The experimental results show that, Benzimidazole corrosion inhibitor in 0.1M H2SO4 solution for Q235 steel has certain inhibition effect, when the substituent is not at the same time, the inhibition efficiency of different molecules are. The omeprazole in the concentration of 1 × 10-3M, the highest inhibition efficiency is about 98%. Four kinds of organic corrosion inhibitor performance ranking for comprehensive analysis: Omeprazole>2-Phenylbenzimidazole>2-Aminobenzimidazole>Benzimidazole.(4) The use of quantum chemical methods to calculate the characteristic parameters of four inhibitor molecule, by the relationship between the quantization parameter and corrosion performance, and then analyzes the relationship between the Benzimidazole derivatives and corrosion performance of its molecular structure. The results show that, the highest occupied molecular orbital of EHOMO molecule is bigger, Benzimidazole corrosion inhibitor corrosion inhibition effect is stronger, and the molecular band(E = ELUMO-EHOMO) and dipole moment was smaller, the inhibition effect is better. Comprehensive analysis of four kinds of inhibitors of the inhibition efficiency order should be: Omeprazole > 2-Phenylbenzimidazole > 2-Aminobenzimidazole >Benzimidazole. Conclusion and the experimentally measured corrosion rate size order is consistent.