Inhibition of aluminum corrosion by phthalazinone and synergistic effect of halide ion in 1.0Â M HCl

► The inhibition ability of PTO with 0.1% KI for Al2024 acid corrosion was studied. ► IE% found to increase with the increase in inhibitor concentration. ► IE% further increase with presence of 0.1% KI due to synergistic effect. ► A competitive mechanism exists between iodide anion and PTO cations. ► The adsorption of PTO in absence and presence of KI obeys the Freundlich and Langmuir adsorption isotherms, respectively.