Electrochemical Studies on New Pyridazinium Derivatives as Corrosion Inhibitors of Carbon Steel in Acidic Medium

Two pyridazine derivatives “1-decylpyridazin-1-ium iodide” (DPI) and “1-tetradecylpyridazin-1-ium iodide” (TPI) were synthesized and investigated as corrosion inhibitors for carbon steel in HCl (1 M) solution. In order to evaluate the anticorrosion activity of these compounds, the electrochemical impedance spectroscopy was performed at different concentrations and at various temperatures (303–333 K). The collected results showed that DPI and TPI reached a value of 86.7% and 88.6% at 10⁻³ M, respectively (303 K). The decrease of the double-layer capacitance for TPI became more remarkable with increase in temperature. The adsorption of both inhibitors on mild steel surface obeyed the Langmuir adsorption isotherm. An inhibition efficiency of 97.6% was obtained at the optimum concentration (10⁻³ M) following an immersion period of 12 h. The quantum chemical calculations based on DFT method supported the experimentally obtained results.