Ce(NO3)(3) and Na2MoO4 are adopted to form (Mo-Ce) composite corrosion inhibitor in allusion to the corrosion problem of steel in acidic conditions. The experimental results showed that the anticorrosion effects were enhanced and the inhibition efficiencies were increased by (NH4)(2)S2O8. The reason of enhancement is the increase of coordination bonds amount between Ce4+ and MoO42-, the augment of combining sites of interface between anti-corrosion film and steel, and the reinforce of adsorption caused by the transformation of Ce(3+)to Ce4+ by oxidants. The process and conditions for transformation of Ce3+ to Ce4+ and formation of complexes are discussed. The related thermodynamic and kinetic parameters are calculated and the possibility for (NH4)(2)S2O8 to improve the performance of Mo-Ce corrosion inhibitor is proved. (C) 2014 Elsevier B.V. All rights reserved.