Temperature Dependence of Dissolution at Dislocations on the (111) Surface of Copper Crystal under Potentiastatic Electrolysis

The (111) surface of copper crystal was etched electrolytically under a constant overpotential of 143±10 mV in a solution containing 5 kmol\u27m-3 NaCI, 0.25 kmol\u27m-3 NaBr and 10-4 kmol\u27m-3 CuCI at different temperatures from 275 to 307 K. The depth and width of dislocation etch pits and the dissolved amount of a matrix surface were measured using optical and interference microscopes. From the variation of these quantities with an etching time, thevertical dissolution rate along a dislocation line, Vd, the lateral one, 1.>, and the vertical one of matrix surface, v" were determined. These dissolution rates showed a very different dependence on etching temperature. The value of log Vdincreased steeply at a low temperature and then decreased gradually with an increase of temperature. The value of log v, increased more slowly at higher temperatures. On the other hand, log 1.> increased linearly with an increase of temperature. These temperature dependencies were discussed on the basis of the nucleation theory of crystal dissolution