Abstract:

Four 2,5-diaryl-1,3,4-thiadiazole compounds, namely, 2,5-diphenly-1,3,4-thiadiazole (DPTD), 2,5-di(2-hydroxyphenly)-1,3,4-thia-diazole (2-DHPTD), 2,5-di(3-hydroxyphenly)-1,3,4-thiadiazole (3-DHPTD), and 2,5-di(4-hydroxyphenly)-1,3,4-thiadiazole (4-DHPTD) were synthesized. Their corrosion-inhibiting performance in S-ethanol system was evaluated by Tafel polarization and electrochemical impedance spectroscopy (EIS). Electrochemical experimental results showed that all the thiadiazole derivatives were excellent inhibitors. The corrosion current decreased and the inhibition efficiency increased with increasing concentrations of the inhibitors. The optimum concentration was 90 mg·L^-1, while the inhibition efficiency of DPTD, 2-DHPTD, 3-DHPTD and 4-DHPTD was 85.8%, 94.6%, 96.4% and 97.1%, respectively. Scanning electronic microscope (SEM) and atom force microscope (AFM) were also carried out, and confirmed the existence of the adsorbed film which was prevailed in addition of thiadiazole derivatives. The adsorption of these compounds onto silver surface from 50 mg·L^-1 S-ethanol was followed the Langmuir adsorption isotherm and attributed to mixed-type adsorption mainly dominated by chemisorption. Quantum chemical calculations and molecular dynamic simulations also demonstrated that thiadiazole derivatives were good inhibitors. The experimental results showed that the order of inhibition efficiency was [4-DHPDT]> [3-DHPDT]> [2-DHPDT]> [DPDT], which was agreed with the theoretic method.

Key words: thiadiazole derivatives, inhibitor, Langmuir adsorption isotherm, molecular dynamic simulations, quantum chemical calculations

摘要：

合成4种2,5-二芳基-1,3,4-噻二唑化合物,即2,5-二苯基-1,3,4-噻二唑(DPTD),2,5-二(2-羟基苯)-1,3,4-噻二唑(2-DHPTD),2,5-二(3-羟基苯)-1,3,4-噻二唑(3-DHPTD)和2,5-二(4-羟基苯)-1,3,4-噻二唑(4-DHPTD)。通过Tafel极化曲线和电化学阻抗研究4种油溶型噻二唑衍生物在50 mg·L^-1硫-乙醇体系中的缓蚀性能,电化学测试表明:腐蚀液中添加噻二唑衍生物后,银片腐蚀得到抑制;随着缓蚀剂浓度增大,腐蚀电流密度减小,缓蚀效率增大;当缓蚀剂浓度为90 mg·L^-1时,4种缓蚀剂DPTD、2-DHPTD、3-DHPTD和4-DHPTD的缓蚀效率分别为85.8%、94.6%、96.4%和97.1%。采用扫描电子显微镜和原子力显微镜观察其表面形貌,可知缓蚀剂在金属表面形成一层保护膜,阻止腐蚀物质与金属表面的接触,从而抑制银片腐蚀。经分子动力学分析可知,4种噻二唑衍生物吸附于金属表面遵循Langmuir等温方程,且吸附属于以化学吸附为主的混合型吸附。量子化学计算和分子动力学模拟研究表明,4种缓蚀剂均具有很好的缓蚀作用,且4种缓蚀剂的缓蚀效率大小顺序是[4-DHPDT]> [3-DHPDT]> [2-DHPDT]> [DPDT],这与实验结果一致。

关键词: 噻二唑衍生物, 缓蚀剂, Langmuir吸附等温方程, 分子动力学模拟, 量子化学计算