An experimental and theoretical study of two pyridinium salt derivatives as API 5L Grade B steel corrosion inhibitors in H2SO4 solution

The inhibition of API 5L Grade B steel corrosion in sulfuric acid solution in the presence of some pyridinium salt derivatives such as 1,1 '-methylenebis(pyridin-1-ium)bromide (pyridinium salt 1 ) and 1,1 '-(ethane-1,2-dyl))bis(pyridin-1-ium)bromide (pyridinium salt 2 ) was conducted using weight loss techniques, potentiodynamic polarization methods, electrochemical impedance spectroscopy (EIS), atomic force microscopy (AFM) and theoretical calculations. Various parameters were determined and discussed to fully understand the mode of action of these compounds, including thermodynamic activation, adsorption, and quantum chemical parameters. The results obtained by all techniques revealed that these derivatives are suitable inhibitors for this type of steel in sulfuric acid solutions. In addition, the inhibition efficiency increases with pyridinium salt concentration and temperature. The polarization curves show that both pyridinium salts are mixed-type inhibitors. Electrochemical impedance spectroscopy (EIS) indicates that charge transfer controls the corrosion process of steel in the absence and presence of compounds. The adsorption of each compound occurs via electrostatic and chemical bonds and obeys Langmuir ' s adsorption isotherm. AFM images demonstrate that these salts protect this steel in H2SO4 solution. Theoretical calculations indicate a correlation between the experimental and quantum parameters.