Assessment of activated polyacrylamide and guar as organic additives in copper electrodeposition

Abstract

The effect of current density, temperature, diffusion layer thickness (δ), deposition time, Guarfloc66 (Guar) and activated polyacrylamide (APAM) on the topography (surface roughness) of electrodeposited copper was studied. The level of these variables approximates current commercial copper electrowinning (EW) and electrorefining (ER) operating conditions. The effect of Guar and APAM on surface roughness and number of Peaks-per-Centimeter was assessed both in combination and alone using a rotating cylinder electrode (RCE) for up to 6-hour EW time. Observed effects on surface roughness indicate that a more uniform surface and lower roughness/smoother copper deposits were obtained using the additive APAM rather than Guar. Regression models indicate APAM has a significant effect on reducing surface roughness at 65 °C.

Bench-scale continuous electrowinning tests were carried out at 50 °C for 44.6 h using parallel plate electrodes into which APAM and Guar were dosed continuously and independently. These tests also indicated that APAM produces smoother deposits than Guar. The cross sections of the copper deposits from these tests showed that APAM exhibits a slightly columnar copper deposit and Guar produced a porous copper deposit. The copper deposit produced with additive APAM was brighter and produced greater amounts of both smaller and larger crystallite sizes than those obtained with Guar. This infers that APAM favours higher nucleation rates and greater 3D crystallite growth and coalescence than Guar.