硫酸介质中丙氨酸复合缓蚀剂的研究

目的研究丙氨酸和碘化钾共同存在于硫酸溶液中,对碳钢的协同缓蚀作用。方法采用极化曲线、交流阻抗谱、扫描电镜、X射线光电子能谱(XPS)以及El-Awady动力学模型,对丙氨酸、丙氨酸与碘化钾复配缓蚀剂对碳钢在硫酸介质中的缓蚀性能和吸附机理进行探究。结果在10%的硫酸体系中,对碳钢的缓蚀性能随着缓蚀剂浓度增大而增强。单独使用丙氨酸作为缓蚀剂,丙氨酸分子在碳钢表面呈单分子层吸附,缓蚀效率最高仅达到29%,缓蚀效果不明显。经过丙氨酸与碘化钾复配后,缓蚀效果显著提高,当丙氨酸质量浓度为300 mg/L,碘化钾质量浓度为250 mg/L时,缓蚀效率达到92%以上。XPS谱图表明,缓蚀剂主要是通过分子中的N原子与碳钢表面Fe原子形成共价键,吸附在碳钢的表面,与KI复配后,I-吸附在碳钢表面,并部分氧化,形成I_3~-。El-Awady动力学模型研究说明该复配缓蚀剂为混合型缓蚀剂,且在碳钢表面自发形成多分子层吸附膜。结论在10%的硫酸溶液中,丙氨酸分子通过物理吸附或化学吸附作用,吸附在碳钢表面,减缓腐蚀反应发生。碘化钾添加后,发挥连接缓蚀剂分子和碳钢表面的桥梁作用,从而协助丙氨酸吸附到碳钢表面,提高丙氨酸在碳钢表面的覆盖率,在提高缓蚀效率的同时,减少了丙氨酸的使用量,有效地抑制了钢材的腐蚀。

Complex Corrosion Inhibitor of Alanine in Sulfuric Acid Medium

The work aims to study the synergistic effect of alanine and KI coexisting in H2SO4 solution on corrosion inhibition of carbon steel. The anticorrosion performance and adsorption mechanism of alanine and complex inhibitor of alanine and KI on carbon steel were studied with dynamic polarization curves, electrochemical impedance spectroscopy, SEM, X-ray photoelectron spectroscopy (XPS) and El-Awady dynamic model. The anticorrosion performance of corrosion inhibitors on carbon steel improved with increasing of concentration in the 10% H2SO4 solution. When the alanine was used as corrosion inhibitor alone, the adsorption of the alanine molecular was monolayer, the inhibition efficiency was only up to 29% and the corrosion inhibition effect was not significant. However, when the alanine and KI coexisted in the solution, the corrosion inhibition effect was improved remarkably. When the mass concentration of alanine was 300 mg/L, and KI mass concentration was 250 mg/L, the corrosion inhibition efficiency could reach about 92%. XPS results showed that the corrosion inhibitor was mainly adsorbed on the surface of carbon steel by forming covalent bonds between N and Fe atoms. When KI was added, I- was adsorbed on the metal surface and oxidized to I3- partly. The El-Awady dynamic model indicated that the compounded corrosion inhibitor was mixed type and the adsorption process was multi-molecular layer adsorption. In 10% sulfuric acid solution, alanine molecules are adsorbed on the surface of carbon steel through physical adsorption or chemical adsorption to slow down corrosion reaction. After added, the KI acts as a bridge connecting inhibitor molecules with the carbon steel surface, thus assisting alanine to adsorb to the carbon steel surface, improving the coverage rate of alanine on the carbon steel surface, increasing the corrosion inhibition efficiency, reducing the use amount of alanine, and effectively inhibiting the corrosion of steel.