An aqueous extract of Andrographis paniculata has been used as corrosion inhibitor, in controlling corrosion of mild steel in simulated oil well water (SOWW). Weight loss method reveals that 10 mL of the extract offers 94% inhibition efficiency to mild steel immersed in simulated oil well water (SOWW). The mechanistic aspects of corrosion inhibition have been investigated by electrochemical studies such as polarization study and AC impedance spectra. Polarisation study reveals that the inhibitor system controls the cathodic reaction predominantly as revealed by the shift of the corrosion potential to the cathodic side in presence of the inhibitor system. The corrosion protective nature of the inhibitor is confirmed by the increase in the linear polarization resistance value and decrease in the corrosion current value. The formation of a protective film on the metal surface is confirmed by the AC impedance spectra. This is confirmed by the fact that there is increase in charge transfer resistance value and decrease in double layer capacitance value. The adsorption of the inhibitor molecule obeys Langmuir adsorption isotherm. The protective film has been analyzed FTIR spectra. It confirms that the inhibitor has coordinated with ferrous ion the metal surface through the polar atoms of the inhibitor molecule. The surface morphology of the protective film has been investigated by SEM and AFM. It is observed that in presence of inhibitor the surface of the corroded metal becomes smoother. The Vickers hardness of the metal surface before experimentation and after experimentation has been measured. It is observed that the surface becomes harder in presence of inhibitor than in the absence of inhibitor under the influence of corrosive medium, namely simulated oil well water. The findings have potential application in petroleum industry. The inhibitor extract can be added along with the simulated oil well water in the pipelines made of mild steel.

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穿心莲的水提取物抑制模拟油井水中低碳钢的腐蚀

穿心莲的水提取物已被用作缓蚀剂，用于控制模拟油井水（SOWW）中低碳钢的腐蚀。失重法表明，浸入模拟油井水（SOWW）中的低碳钢中10毫升的提取物可提供94％的抑制效率。腐蚀抑制的机理已通过电化学研究进行了研究，例如极化研究和交流阻抗谱。极化研究表明，缓蚀剂系统主要控制阴极反应，如存在缓蚀剂系统时腐蚀电位向阴极侧的转移所揭示。通过线性极化电阻值的增加和腐蚀电流值的减少来确认抑制剂的腐蚀防护性质。通过AC阻抗谱确认在金属表面上形成保护膜。这由以下事实证实：电荷转移电阻值增加而双层电容值减小。抑制剂分子的吸附遵循Langmuir吸附等温线。该保护膜已经过FTIR光谱分析。这证实了抑制剂已经通过抑制剂分子的极性原子与亚铁离子配位了金属表面。通过SEM和AFM研究了保护膜的表面形态。观察到在存在抑制剂的情况下，腐蚀的金属的表面变得更光滑。测量了实验之前和实验之后的金属表面的维氏硬度。可以看出，在腐蚀介质（即模拟油井水）的影响下，存在抑制剂的情况下的表面比不存在抑制剂的情况下的表面变硬。这些发现在石油工业中具有潜在的应用。抑制剂提取物可以与低碳钢制成的管道中的模拟油井水一起添加。