Enhanced corrosion inhibition of carbon steel by pyridyl gemini surfactants with different alkyl chains

Three pyridyl gemini surfactants varying in alkyl chain length (DBP: decamethylene bis-pyridinium dibromide; OBP: octamethylene bis-pyridinium dibromide; HBP: hexamethylene bis-pyridinium dibromide.) were applied as corrosion inhibitors for the first time. The inhibition performance of three inhibitors on P110 steel corrosion in HCl solution were studied using gravimetric measurement, electrochemical analysis, scanning electron microscopy (SEM), and quantum chemical calculation. Adsorption of inhibitors onto the steel surface was described well by Langmuir isotherm. All of three compounds were mixed-type inhibitors. The inhibition efficiency of the three inhibitors was in the order: DBP > OBP > HBP, especially as high as efficiency of 91.76% in case of DBP. Increment of the non-polar chain length within the inhibitor contributed to the improvement of corrosion inhibition, which may be due to the stronger hydrophobicity with longer alkyl chain. Results in this study reveal the potential application of non-polar pyridinium gemini surfactants as excellent inhibitors, providing new ideas for synthesizing novel corrosion inhibitor.