Three new Schiff bases, viz., N,N'-ethylen-bis (salicylidenimine) [S-1], N,N'-isopropylien-bis (salicylidenimine) [S-2], and N-acetylacetone imine, N'-(2-hydroxybenzophenone imine) ortho-phenylen [S-3] have been investigated as corrosion inhibitors for mild steel in 0.5 M H2SO4 using Tafel polarization and electrochemical impedance spectroscopy (EIS). The three Schiff bases function as good inhibitors reaching inhibition efficiencies of similar to 97-98% at 300ppm concentration. The fraction < theta > of the metal surface covered by the inhibitor is found to increase with inhibitor concentration. Of the three Schiff bases, the S2 shows better efficiency than the other two Schiff bases. The adsorption of the inhibitor follows Langmuir isortherm. Thermodynamic calculations indicate the adsorption to be physical in nature. (c) 2006 Elsevier Ltd. All rights reserved.