Abstract The castor oil as a cheap and environmentally friendly source was used to prepare a novel green corrosion inhibitor for mild steel in acidic medium. The poor performance at high temperatures and low biodegradability are two important challenges of corrosion inhibitors that castor oil-based corrosion inhibitor (COCI) is designed to overcome them. The inhibition performance of COCI was evaluated by weight loss, open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and polarization techniques. The morphology of MS was examined by field emission scanning electron microscope (FESEM), energy dispersive X-ray (EDX) and atomic force microscopy (AFM). Furthermore, a comprehensive computational study was done to clarify the anticorrosive mechanism of COCI by molecular dynamics (MD) simulation, density functional based tight-binding (DFTB) approach and density functional theory (DFT). Maximum inhibition efficiency of 85 % and 91 % were achieved at 80 °C using 140 μM of COCI in EIS and polarization tests, respectively. COCI acted as a mixed type inhibitor and the adsorption of the inhibitor on the mild steel surface was chemisorption. The obtained results demonstrate that the COCI has a considerable ability to suppress acidic corrosion at all concentrations were studied here, particularly at high temperatures. Given the fact that several articles were reported a significant reduction in performance of corrosion inhibitors by increasing temperature, in this study was found out not only was there no decrease in inhibition efficiency of COCI at higher temperatures, but it depicted good performance at 80 °C. In addition, the high adsorption energy of COCI confirmed a strong interaction between Fe surface and inhibitor molecules and showed a significant effect of the urethane bonds and the triglyceride groups on molecular activity. The Fermi energy state indicated that the chemical adsorption occurred in the interaction of COCI-Fe surface by electron transition from inhibitor to Fe 3d band state. We expect the results of this work provide new opportunities for the design and synthesis of efficient corrosion inhibitors based on vegetable oils.

中文翻译：

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蓖麻油基缓蚀剂在酸性介质中高温缓蚀低碳钢的理论与实验研究

摘要 利用蓖麻油作为一种廉价且环保的原料，在酸性介质中制备了一种新型低碳钢绿色缓蚀剂。高温下性能差和生物降解性低是缓蚀剂的两个重要挑战，蓖麻油基缓蚀剂 (COCI) 旨在克服它们。通过失重、开路电位（OCP）、电化学阻抗谱（EIS）和极化技术评价COCI的抑制性能。通过场发射扫描电子显微镜 (FESEM)、能量色散 X 射线 (EDX) 和原子力显微镜 (AFM) 检查 MS 的形貌。此外，通过分子动力学（MD）模拟，进行了全面的计算研究，以阐明 COCI 的防腐机制，基于密度泛函的紧束缚 (DFTB) 方法和密度泛函理论 (DFT)。在 EIS 和极化测试中，使用 140 μM C​​OCI 在 80 °C 下分别实现了 85% 和 91% 的最大抑制效率。COCI作为混合型缓蚀剂，缓蚀剂在低碳钢表面的吸附为化学吸附。获得的结果表明，COCI 在所有浓度下都具有相当大的抑制酸性腐蚀的能力，特别是在高温下。鉴于有几篇文章报道了升高温度会显着降低缓蚀剂性能的事实，在本研究中发现，不仅在较高温度下 COCI 的缓蚀效率没有降低，而且在 80 °C 下表现出良好的性能. 此外，COCI 的高吸附能证实了 Fe 表面和抑制剂分子之间的强相互作用，并显示出氨基甲酸酯键和甘油三酯基团对分子活性的显着影响。费米能态表明化学吸附发生在 COCI-Fe 表面的相互作用中，通过从抑制剂到 Fe 3d 带态的电子跃迁。我们期望这项工作的结果为基于植物油的高效腐蚀抑制剂的设计和合成提供新的机会。费米能态表明化学吸附发生在 COCI-Fe 表面的相互作用中，通过从抑制剂到 Fe 3d 带态的电子跃迁。我们期望这项工作的结果为基于植物油的高效腐蚀抑制剂的设计和合成提供新的机会。费米能态表明化学吸附发生在 COCI-Fe 表面的相互作用中，通过从抑制剂到 Fe 3d 带态的电子跃迁。我们期望这项工作的结果为基于植物油的高效腐蚀抑制剂的设计和合成提供新的机会。