苯基和苯甲酰基硫脲在盐酸中的缓蚀性能和机理分析

Corrosion Inhibition Performance and Mechanism Analysis of Phenyl and Benzoyl Thiourea in Hydrochloric Acid

余 意 刁 欢 王 恒 肖 谭 曾春珉 王应好 张 健

YU Yi DIAO Huan WANG Heng XIAO Tan ZENG Chunmin WANG Yinghao ZHANG Jian

为了深入理解硫脲基酸化缓蚀剂的缓蚀作用机制，提高硫脲基缓蚀剂在酸化开发过程中的应用效果，利用 腐蚀失重实验、扫描电子显微镜、量子化学计算研究了两种硫脲衍生物苯基硫脲（PHTU）和苯甲酰基硫脲（BOTU）在15% HCl溶液中对20#钢的缓蚀性能和缓蚀机理。结果表明，PHTU和BOTU对20#钢在15% HCl溶液中 均有较好的缓蚀效果。加量为2 mmol/L时，钢片表面形成的较为致密完整的腐蚀产物可抑制腐蚀性介质与钢基 体的接触，缓蚀率可达83%以上，且由于BOTU分子中C=O双键的存在，BOTU的缓蚀性能优于PHTU。PHTU 和BOTU在钢表面的吸附均符合Langmuir吸附模型，吸附方式为物理吸附和化学吸附共存的混合吸附。量子化 学计算结果表明，缓蚀剂分子中的反应活性位点主要分布在C=S双键、C—N键及BOTU的C=O双键上。其中， N原子被酸液质子化后可与钢表面通过静电引力形成物理吸附；高电子云密度的C=S键、C=O键及苯基可提供 电子与铁原子的空d轨道，通过配位和反馈键形成化学吸附，进而稳定吸附在金属表面形成保护膜，抑制腐蚀进程。

In order to deeply understand the corrosion inhibition mechanism of thiourea-based acidizing corrosion inhibitors and improve the application effect of corrosion inhibitors in acidizing development process，the corrosion inhibition performance and corrosion inhibition mechanism of two thiourea derivatives，such as phenyl thiourea（PHTU）and benzoyl thiourea（BOTU）on 20# steel in 15% HCl solution were studied by corrosion weight loss experiment，scanning electron microscope and quantum chemical calculation. The results showed that PHTU and BOTU had good corrosion inhibition effect on 20# steel in 15% HCl solution. When the concentration of corrosion inhibitor was 2 mmol/L，the dense and complete corrosion product formed on the surface of steel sheet could inhibit the contact between corrosive medium and steel substrate. The corrosion inhibition rate could reach more than 83%. Moreover，with the presence of C=O double bond in BOTU molecule，the corrosion inhibition performance of BOTU was better than that of PHTU. The adsorption of both PHTU and BOTU on steel surface was in accordance with the Langmuir adsorption model. The adsorption mode was a mixture of physical and chemical adsorption coexisting. Quantum chemical calculations showed that the reactive sites in corrosion inhibitor molecule mainly distributed on C=S double bond，C—N bond and C=O double bond of BOTU. Nitrogen atoms protonated by the acid could form physical adsorption with steel surface through electrostatic gravitational attraction. The C=S bond，C=O bond and phenyl group with high electron cloud density could provide electrons to form chemisorption with the empty d orbitals of Fe atoms through coordination and feedback bonding，which in turn stabilized the adsorption on metal surface to form a protective film and inhibit the corrosion process.

10.19346/j.cnki.1000-4092.2023.01.019