The inhibition mechanism of imidazoline phosphate inhibitor for Q235 steel in hydrochloric acid medium

► Inhibition efficiency increase with the inhibitor concentration in 1 M HCl solution. ► The imidazoline phosphate inhibitor is a kind of mixed-type inhibitor. ► The adsorption of imidazoline phosphate on Q235 steel follows Langmuir isotherm. ► Imidazoline ring and the heteroatoms are the active sites of the studied inhibitor.