화학공학소재연구정보센터
Journal of the Electrochemical Society, Vol.164, No.12, C611-C617, 2017
Influence of Copper on Trivalent Chromium Conversion Coating Formation on Aluminum
In the present work, modified copper-containing trivalent chromium conversion (TCC) coating processes for aluminum were investigated. The copper addition to the TCC bath was made for the purposes of reducing the generation of hydrogen peroxide and chromium (VI) species during the coating growth. The morphologies and compositions of the coatings were examined using high-resolution electron microscopy, energy-dispersive X-ray spectroscopy and Raman spectroscopy. UV photometric measurements were employed to determine the amount of hydrogen peroxide in the TCC solution. The resultant coatings contained zirconium oxides, chromium hydroxide and fluorides and sulfate constituents, as well as copper oxides and copper-rich deposits that were preferred cathodic sites for oxygen reduction. Of most significance, no chromium (VI) species were detected in the coatings by Raman spectra. It is suggested that this results from reduced generation of hydrogen peroxide, as disclosed by photometric measurements, at the cathodic copper-rich particles, due to favoring of the four electron oxygen reduction reaction. (C) The Author(s) 2017. Published by ECS. All rights reserved.