Studying the Effect of Butanol on the Anode Behavior of Copper in Phosphoric Acid Solutions

Abstract

The anode behavior of the copper electrode immersed in butanol phosphate electrolytes has been studied. The polarization dependences of the electrode allowed us to detect the sections that correspond to the passive and active states of copper and we also established the zone of the combined behavior of the processes of the copper dissolution and oxygen release. It was also established that a butyl alcohol contributes to an abrupt decrease in current densities in the entire region of anode potentials. The addition of butanol conditions the disappearance of current oscillations that can be seen on polarization dependences in phosphate solutions. Evidently, a decrease in the current densities is a consequence of the butanol adsorption on the copper surface and its participation in the formation of passive films. The specific features of the copper passivation in butanol phosphate electrolytes are characterized by the appearance of the explicit current peak that separates active and passive state zones at the ratio of C4H9OН:H3PO4 =1:3.As the alcohol-to-acid ratio increases, the peak gradually decreases. The addition of butanol has no determining influence on the potential value that corresponds to the started oxygen release. Currentefficiency values for the copper dissolution depend on the anode current density ja and the electrolyte composition. An increase in ja results in a decreased current efficiency value. An increase in the С4Н9ОН content has a similar action. Maximum current efficiency values are observed at ja=0.5–2 А∙dm-2, and they correspond to the active copper state. The dependences obtained for the copper dissolution rate allowed us to establish that υрalso increases with an increase in the current density up to ja=20 А∙dm-2. The copper treatment quality depends on the current density and the electrolyte composition. The solutions with the ratio of C4H9OН:H3PO4=2:1fail to provide a high quality treatment; the surface is not glossy and it has grinding traces. A high-quality treatment is observed in the electrolytes with the ratio of C4H9OН:H3PO4 =1:2 and lower. The electrochemical polishing in such solutions results in the glossy copper surface with the smoothed relief and it has no polishing traces.