The molecular behavior of some pyridine derivatives as corrosion inhibitors of iron and aluminum in acid media, were studied quantum electrochemically. The calculations were made for three conditions; isolated inhibitor molecule, metal cluster, and finally polarized continuum media. It is concluded that for aluminum the vertical adsorption through nitrogen atom is prevailing, while for iron both vertical and planar adsorptions (through π electrons of aromatic ring) are possible, but the vertical is predominant. The inhibitor chemical potential (μ) and the extent of charge transfer (ΔN) to the metal were determined. A linear correlation between each of these and the inhibition efficiencies are demonstrated. Finally, from the calculated de-solvation free energy values as a function of dielectric constant, it is observed that there is an abrupt decrease in the free energies as the inhibitor molecule enters EDL. Also the calculated de-solvation free energies show a linear correlation with experimental inhibition efficiencies.