Effective inhibition of P11 steel corrosion in 1.0 M HCl solution using aged potassium iodide: Gravimetric, electrochemical, thermodynamic and kinetic studies

Potassium iodide (KI) has been widely studied as an optimal synergist with various corrosion inhibitors.However, there is significant disagreement regarding the inhibitory efficacy of KI as an individual inhibitor, resulting in a variety of synergy coefficient results when evaluating its synergistic impact.The aim of this study was to investigate aged KI for 24 h in 1 M HCl as a corrosion inhibitor for P11 steel at 25, 45, and 65C.Gravimetric (WL), potentiodynamic polarization (PDP), linear polarization resistance (LPR), electrochemical frequency modulation (EFM), and electrochemical impedance spectroscopy (EIS) techniques were used.The inhibition efficiency of aged KI increases with its concentration and temperature.The highest inhibitory effectiveness, depending on the technique used, was determined to be 92.31%(PDP), 90.49% (LPR), 92.7% (EFM), 90.7% (EIS), and 87.19% (WL) at 65C and 5 mM aged KI.The PDP results revealed that aged KI acts as a mixed-type inhibitor.The adsorption of iodide ions on the surface of P11 steel obeys the Langmuir adsorption isotherm.The thermodynamic parameters of adsorption and activation support a mixed adsorption process involving physisorption and chemisorption.