On the kinetics of chromium electrodeposition on copper electrodes

In a previous work, we observed that, during cyclic potentiodynamic curves of cathodic polarisation (from 0.00 to - 1.25 V/SCE, 5 mV s(-1)) in chromic acid solution of industrial composition, ARMCO iron undergoes a pitting co rrosion, while carbon steels undergo a selective ferritic corrosion. Bliste rs of pure iron were also observed on ARMCO iron electrodes surface. These occurrences suggest a direct participation of the metal substrate to the ov erall reaction of reduction of the chromic acid to chromium metal. Therefor e, the chemical nature of the electrode metal has been changed, in order to pl avc that the chromium reduction goes on through an ECE mechanism involv ing a fast chemical reaction between unstable intermediate chromium reducti on goes and the metal substrate. Cathodic potentiodynamic polarisation curv es were performed on copper electrodes and the scans were stopped at four d ifferent potentials (-0.90, - 1.00, -1.10 and -1.25 V/SCE). The copper surf ace undergoes a severe corrosion in all the experimental conditions. The mo rphology of the attack depends on the polarisation potential and on the pre sence of additives in solution, like iron sulphate. (C) 2001 Elsevier Scien ce B.V. All rights reserved.