竹叶提取物对铝在HCl溶液中的缓蚀作用

用不同浓度的C₂H₅OH（体积分数：20%-80%）从金竹竹叶中提取制备出竹叶缓蚀剂（简称为PSLE），用紫外-可见（UV-Vis）光谱和傅里叶变换红外（FTIR）光谱对其进行了表征，并对总黄酮含量进行了测定. 采用失重法、动电位极化曲线、电化学阻抗谱（EIS）和扫描电子显微镜（SEM）研究PSLE在HCl 介质中对铝的缓蚀作用.采用量子化学密度泛函理论（DFT）研究了两个主要竹叶黄酮成分牡荆苷和异牡荆苷的吸附方式. 结果表明：PSLE对铝具有良好的缓蚀作用，且在铝表面的吸附符合Langmuir 吸附等温式. 缓蚀率随其浓度的增加而增大，但随温度的升高和盐酸浓度的增加而降低. 竹叶总黄酮含量和竹叶缓蚀剂的缓蚀性能有良好的相关性，初步推测竹叶缓蚀剂的有效成分主要为竹叶黄酮类化合物. PSLE为阴极抑制型缓蚀剂；EIS 在高频区呈容抗弧，在低频区呈感抗弧，添加PSLE后，阻抗值显著增大. SEM表明添加PSLE对铝的腐蚀产生了明显的抑制作用.量子化学计算结果表明，牡荆苷和异牡荆苷的吸附中心主要集中在竹叶黄酮骨架（FBS）.

Inhibition Effect of Bamboo Leaf Extract on the Corrosion of Aluminum in HCl Solution

A bamboo leaf inhibitor (designated PSLE) was extracted from Phyllostachys sulphurea (Corr. Riviere) leaves using a series of C₂H₅OH-water solutions (20%-80% (volume fraction)). The solutions were characterized by Fourier transform infrared (FTIR) spectroscopy and ultraviolet- visible (UV-Vis) spectrophotometry. The total flavonoid content of the PSLE was determined. The inhibition effect of PSLE toward the corrosion of aluminum in HCl solution was studied by weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM). Density functional theory (DFT) quantum chemical calculations including solvent effects were used to investigate the adsorption of light by the two major components vientin and isovientin. The results show that PSLE is a good inhibitor and the adsorption of PSLE on the aluminum surface obeys the Langmuir adsorption isotherm. The inhibition efficiency increases with PSLE concentration while it decreases with temperature and HCl concentration. A good correlation exists between the total flavonoid content and the inhibition performance. This implies that the flavonoids are the major contributor to inhibition activity. PSLE behaves as a cathodic inhibitor. The EIS spectra are characterized by one large capacitive loop at high frequencies followed by a large inductive loop at low frequency values. The impedance value increases with increasing inhibitor concentration. SEM results confirm that the corrosion of aluminum is retarded remarkably by PSLE. The quantum calculation results indicate that the adsorption center of either vientin or isovientin is mainly a flavonoid backbone structure (FBS).