Thermodynamic Calculation of Flade Potential of Fe, Ni, and Cr Taking into Account Surface Energy
Yu. Ya. Andreev
Moscow Institute of Steel and Alloys, State Technological University, Leninskii pr. 4, Moscow, 119049 Russia
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Received May 20, 2009
Abstract — A method for the thermodynamic estimation of the active–passive transition potential of metals (Flade potential) in sulfuric acid (pH 0) is proposed. This theoretical calculation of the Flade potential (
) differs from the conventional one in that the Gibbs formation energy of the metal oxide on the surface 
is a sum of the Gibbs formation energy of the oxide 
< 0 and the surface Gibbs energy of the metal
> 0. The technique of 
estimation used is based on the concept of the auto-adsorption of metal atoms (A) in the superficial layer and obeys the Gibbs adsorption equation 
= 
GA
A. The estimated Flade potentials of Ni, Cr, and Fe agree with the known experimental data.
) differs from the conventional one in that the Gibbs formation energy of the metal oxide on the surface is a sum of the Gibbs formation energy of the oxide < 0 and the surface Gibbs energy of the metal> 0. The technique of estimation used is based on the concept of the auto-adsorption of metal atoms (A) in the superficial layer and obeys the Gibbs adsorption equation = GAA. The estimated Flade potentials of Ni, Cr, and Fe agree with the known experimental data.
PACS numbers: 82.45.Bb
DOI: 10.1134/S2070205109060057