Abstract

The thermodynamic, inhibitive and synergistic properties of Fragaria ananassa (strawberry) and Cucurbita pepo L (zucchini) leaf extracts on the corrosion of mild steel in Hydrochloric acid solutions were examined by potentiodynamic polarization curves measurements and electrochemical impedance spectroscopy (EIS) technique as well as optical photographic study. Fourier transform infrared spectroscopy (FTIR) and UV-Spectroscopy were applied to predict the possible functional groups and constituents of both leaf extracts. Potentiodynamic polarization curves proved that Fragaria ananassa and Cucurbita pepo L leaf extracts act as mixed type inhibitors for mild steel in 0.5 M HCl solutions. Impedance plots indicated that the corrosion process occurred under activation control. Thermodynamic parameters proved that the formation of the activated complex is an endothermic association instead of a dissociation step. The inhibitive efficiency of these leaf extracts relies on their physical adsorption on the metal surface rather than the complexation with Fe²⁺ ions. Cucurbita pepo L leaf extract is more efficient than Fragaria ananassa as a corrosion inhibitor for mild steel in 0.5 M HCl. The synergistic effect between both extracts may be due to co-adsorption between their molecules, which could be either competitive or co-operative adsorptions. The synergistic parameter value S was higher than unity indicating a cooperative synergistic effect.

中文翻译：

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草莓和南瓜子叶提取物在盐酸溶液中对低碳钢腐蚀的协同作用

摘要

通过电位动力学极化曲线测量和电化学阻抗谱（EIS）技术，研究了草莓（Fragaria ananassa）（草莓）和西葫芦（Cucurbita pepo L，Zucchini）叶片提取物对低碳钢在盐酸溶液中的腐蚀的热力学，抑制和协同特性。光学摄影研究。傅里叶变换红外光谱（FTIR）和紫外光谱用于预测两种叶提取物的可能官能团和成分。电位动力学极化曲线证明了草莓（Fragaria ananassa）和南瓜（Cucurbita pepo）L叶提取物在0.5 M HCl溶液中作为低碳钢的混合型抑制剂。阻抗图表明腐蚀过程在活化控制下发生。热力学参数证明，活化复合物的形成是吸热缔合而不是解离步骤。这些叶提取物的抑制效率取决于它们在金属表面上的物理吸附，而不是与Fe ²⁺离子的络合。西葫芦L叶提取物比草莓属更有效在0.5 M HCl中用作低碳钢的腐蚀抑制剂。两种提取物之间的协同作用可能是由于其分子之间的共同吸附，可能是竞争性吸附或合作性吸附。协同参数值S大于1，表示协同协同效果。