Corrosion inhibitors are widely used in acid solutions during pickling and descaling. Mostly organic compounds containing N, O, and S groups are employed as inhibitors. In this study, the inhibition performance of metal cations such as Zn2+, Mn2+ and Ce4+ ions in the concentration range 1-10 x 10(-3) M has been found out. The corrosion behaviour of iron in 0.5 M H2SO4 in the presence of metal cations is studied using polarization and impedance methods. It is found that the addition of these metal cations inhibits the corrosion markedly. The inhibition effect is in the following order Ce4+ >> Mn2+ > Zn2+. (c) 2005 Published by Elsevier B.V.