The inhibitor effect of N,N'-bis(salicylidene)-2-hydroxy-1,3-propanediamine (LOH) and N,N'-bis(2-hydroxyacetophenylidene)-2-hydroxy-1,3-propanediamine (LACOH) in 2 mol dm(-3) HCl medium on mild steel with known compound has been investigated at 303 K. It has been determined using weight loss, polarization and impedance methods (EIS) that the corrosion rates decrease and percentage inhibition efficiencies and surface coverage degrees increase with increasing additive concentration. The inhibitors appear to function through the Langmuir adsorption isotherm. Results show LACOH to have the highest inhibition efficiency among the two compounds studied. (c) 2005 Elsevier B.V. All rights reserved.