The role of phthalic acid (I) and related compounds, viz., o-phenylenediamine (II) and anthranilic acid (III) to protect aluminium alloy against corrosion in 0.6 M aqueous sodium chloride solution is studied using potentiodynamic polarization technique and impedance studies. The order of inhibition effect of these compounds is found to be I < II < III. Density functional theory (DFT) has been used to analyze the characteristics of the inhibition mechanism and to describe electronic and structural nature of the inhibitor on the corrosion process. Attempt has been made to correlate the inhibiting properties with the electronic parameters and molecular area of the inhibitors