The synergistic inhibition effect of the complex of 2-undecyl-N-carboxymethyl-N-hydroxyethlyimidazoline (UHCI) and potassium iodide (KI) on the corrosion of 45# carbon steel subjected to 4 wt.%citric acid solution is explored by weight loss testing, electrochemical measurement, and X-rayphotoelectron spectroscopy (XPS) analysis. Based on the weight loss test, 94.15% inhibition capacity isobtained by compound inhibitors (UHCI:KI=30:10) after immersion in 4 wt.% citric acid for 8 h, whichis consistent with the results from electrochemical technology. The discussion extends to the effects oftemperature and immersion time to achieve the ideal inhibition performance for further protection. Theadsorption of the studied compound fitted well with the Langmuir isotherm model. The XPS analysisconfirms physical and chemical interactions between the UHCI/KI complex inhibitors and metal surfaceto defend the aggressive electrolyte. Additionally, the corrosion inhibition mechanism of UHCI inhibitorin the presence of iodine ions in the citric acid solution is discussed.
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