METHOD FOR MANUFACTURING CHROMIUM-CHROMIUM OXIDE COATED SUBSTRATES AND COATED SUBSTRATES PRODUCED THEREBY

摘要

The present invention relates to a method for manufacturing a chromium metal - chromium oxide coated substrate by electrolytically depositing a plurality of chromium metal - chromium oxide coating layers on an electrically conductive substrate from an electrolyte solution that comprises a trivalent chromium compound and a chelating agent, wherein the electrolyte solution is free of chloride ions and of a boric acid buffering agent, wherein the electrically conductive substrate acts as a cathode, and wherein an anode comprising a catalytic coating of iridium oxide or a mixed metal oxide or a hydrogen gas diffusion anode is chosen for reducing or eliminating the oxidation of Cr(III)-ions to Cr(VI)-ions, wherein during the deposition of a chromium metal - chromium oxide layer hydrogen bubbles are formed at the strip surface, and wherein between the deposition of the chromium metal - chromium oxide layers, the hydrogen bubbles are removed from the surface of the strip.