Deposition of chromium oxides from a trivalent chromium solution containing a complexing agent for a buffer

A water-soluble composition of matter for electrolytically depositing a chromium oxide coating on a metal substrate comprising a complexing agent for a chrome bath buffer, said complexing agent being present in an amount sufficient to form a complex with any chrome bath buffer introduced into said composition of matter by dragout and thereby reduce chromium deposition and increase chromium oxide deposition on a substrate when electrolytically depositing a chromium oxide coating with said composition, said composition also comprising a trivalent chromium compound, a weak chelating agent, an optional conductivity enhancing cation, an optional depolarizer, and an optional surfactant.

A process of depositing a chromium oxide coating on a metal substrate comprising passing an electrically conductive substrate through a first trivalent chromium bath containing a buffering agent and electrolytically depositing chromium on said substrate to obtain a chromium coated substrate followed by directly passing said chromium coated substrate into a second trivalent chromium bath composition, said second trivalent chromium bath containing said first trivalent chromium bath buffering agent introduced into said second trivalent chromium bath as dragout, said second trivalent chromium bath composition comprising a complexing agent for said buffering agent, in an amount sufficient to increase the formation of a chromium oxide coating, by complexing any of said buffering agent introduced into said second bath by dragout to minimize or eliminate any chrome deposition in said second trivalent chromium bath, said second trivalent chromium bath also comprising a trivalent chromium compound, a weak chelating agent, an optional conductivity enhancing cation, an optional depolarizer, and an optional surfactant, and electrolytically forming a chromium oxide coating on said chromium coated substrate.

A process of depositing a chromium oxide coating on a metal substrate comprising passing an electrically conductive substrate through a first trivalent chromium bath containing a buffering agent and electrolytically depositing chromium on said substrate to obtain a chromium coated substrate followed by directly passing said chromium coated substrate into a second trivalent chromium bath composition, said second trivalent bath composition comprising a complexing agent for said buffering agent to complex said buffering agent introduced into said second trivalent chromium bath composition by dragout, said complexing agent being present in an amount sufficient to reduce chromium deposition and increase chromium oxide deposition in said second trivalent chromium bath, said composition also comprising a trivalent chromium compound, a weak chelating agent, an optional conductivity enhancing cation, an optional depolarizer, and an optional surfactant, and electrolytically forming a chromium oxide coating on said chromium coated substrate.