Steady state kinetics of formation of oxide films on niobium and tantalum metals in malic acid electrolyte at different temperatures

Department of Chemistry, Maharshi Dayanand University, Rohtak-124 001, Haryana, India

E-mail : vermanaveen17@gmail.com

Manuscript received online 30 November 2016, accepted 10 December 2016

Steady state kinetic data from anodic polarization of niobium and tantalum metals under galvanostatic conditions have been obtained over wide range of temperatures and at different current densities in malic acid electrolyte. The obtained data has been analyzed in the light of various theories of ionic conduction. The value of constant A in Guntherschulze and Betz equation is temperature dependent while B is independent of temperature. The constant A is also dependent on the nature of the electrolyte. The data indicates the temperature independent Tafel slope which rules out the applicability of the single barrier theory of Cabrera and Mott. The data has been analyzed in terms of Dignam’s equation. The effects of current density and temperature in aqueous electrolyte on various parameters of Dignam’s equation have been examined.