Role of polyethylene glycol in electrodeposition of zinc-chromium alloys

The role of polyethylene glycol (PEG) as an additive in the electrodeposition of zinc-chromium alloys was investigated in sulfate baths containing trivalent chromium. PEG with high molecular weight enabled the codeposition of metallic chromium with zinc, while chromium(III) was present in the deposits obtained from the baths containing PEG with lower molecular weight as well as the PEG-free bath. The polarization curves for the alloy deposition revealed that PEG with high molecular weight polarized the deposition potential of zinc to the reduction potential of chromium to permit the codeposition of chromium with zinc.