In this study, Koutecky-Levich (K-L) and cyclic voltammetry (CV) techniques were used to measure the kinetic and diffusion parameters for Ce(III) electro-oxidation on glassy carbon in 4 M HNO3 with/without SO42-, Cl-, or Cr2O72- impurities. It was found that the apparent diffusion coefficients (D) of Ce(III) determined using the K-L and CV approaches were 1.65 x 10(-5) and 1.12 x 10(-5) cm(2) s(-1), respectively, while the D value (1.59 x 10(-5) cm(2) s(-1)) from K-L estimation was approximately three times that from the CV approach. The standard rate constants (k degrees) for Ce(III) oxidation estimation from the K-L and CV approaches were 2.63 and 1.80 x 10(-3) cm s(-1), respectively, whereas the k degrees values were lowered by 35-91% and 38-80%, respectively, for the SO42- case and by 46-49 and 33-58%, respectively, for the Cl- case. The multi-impurity case had the lowest rate constant around limiting current for Ce(III) oxidation. The obtained kinetic and diffusion data are useful for the design of Ce(III) to Ce(IV) electro-regenerating systems and the evaluation of using spent Cr-etching solutions as candidate electrolytes in zinc-cerium redox flow batteries (C) 2009 The Electrochemical Society, [DOI: 10.1149/1.3056044] All rights reserved.