The Effect of Addition Agents on Cathode Polarization During Electrodeposition of Copper at Single Crystal Copper Cathodes

Abstract

The polarization-time relations for the initial ( P i ) , maximum (P,,), and pseudo-steady-state (P,) polarizations on copper single crystals in the absence and presence of gelatin and gelatin plus chloride ion were found t o depend upon crystal orientation. The P i and P, , , in the absence of gelatin, the Pi in its presence, and the static potentials were all similarly related to the reticular density. The P i increased, and the time to masimum polarization (t,,,,) decreased, with increase of current density; the relations between these quantities showed marlced differences for the different crystals. The variation with reticular density of Pi and P, , , in the absence of addition agents and of Pi in its presence probably represents differences in activation overpotential a t the various crystal faces. The adsorption of gelatin on different crystal faces was also found to be markedly different. Polarization in the presence of gelatin was decreased by small amounts of chloride ion; a linear relation for all the crystals used was obtained by plotting the increase in polarization caused by gelatin against the decrease caused by 2 mgm./liter chloride ion in the presence of gelatin. In the absence of addition agent, change of acid concentration from 50 to 200 gm./liter had no effect on P i and addition of chloride ion had no effect on P , a t single crystal cathodes.