The adsorption of [(4-hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)-(4-methoxy-phenyl)-methyl]-urea on iron in phosphoric media was studied by using electrochemical technique. The adsorption mechanism was investigated using adsorption isotherms. The experimental data fit localized adsorption models. The values for free energy of adsorption, ΔGads0, were also calculated at each surface coverage, θ of the studied compound by applying the mathematical model of Bockris - Swinkels adsorption isotherm. The variation of free energy of adsorption ΔGads0 with surface coverage, was interpreted in terms of deviation from ideal condition assumed in Langmuir model. A possible adsorption model of HPU2 molecules on to the metal surface was suggested.