TEMPERATURE EFFECTS UPON KINETICS OF CHROMIUM ANODIC-DISSOLUTION IN ACIDIC SULFATE-SOLUTIONS

The influence of temperature (278 - 333 K) upon the kinetics of the an odic dissolution of chromium was studied under nonstationary condition s in acidic sulfate solutions. It was shown that at T greater than or equal to 308 K and T less than or equal to 284 K the chronovoltammetri c curves of monocrystal chromium of {100} crystallographic orientation have one active region at the potentials -0.54 < E < -0.35 V and E > -0.35 V, respectively. At higher temperatures (greater than or equal t o 308 K) Cr dissolves mainly as Cr(II) ions and at lower temperatures (less than or equal to 284 K), as Cr(III) ions. At temperatures betwee n 289 and 303 K, the E vs. j-curves have two active regions at the neg ative potentials, which correspond to the chromium dissolution with th e commensurable rates as Cr(II) and Cr(III). An explanation of the exp erimental results is given with an interpretation of the thermodynamic and kinetic factors that are responsible for partial anodic processes .