A systematic investigation of current efficiency during brass deposition from a pyrophosphate electrolyte using RDE, RCE, and QCM

The pyrophosphate electrolyte has been used for brass deposition as a replacement for cyanide electrolytes. However, there is considerable confusion about the current efficiency of brass deposition from this electrolyte. This study uses a rotating disc electrode (RDE), a rotating cylinder electrode (RCE) and a quartz crystal microbalance (QCM) to systematically determine the current efficiency of copper, zinc, and brass deposition from a pyrophosphate electrolyte. Electrodeposition of brass on RCE and QCM show that the current efficiency for copper, zinc as well as brass is well below 100%. Simultaneous measurement of current and frequency at a QCM showed that pyrophosphate is adsorbed at the electrode surface during copper reduction. However, when zinc is present in the solution, pyrophosphate adsorption is blocked. (C) 2000 Elsevier Science Ltd. All rights reserved.