Electrodeposition Material, Process for Providing a Corrosion-Protective Layer of TiO2 on an Electrically Conductive Substrate and Metal Substrate Coated with a Layer of TiO2

Abstract

The present invention relates to electrodeposition material for the electrochemical deposition of a corrosion-protective layer of TiO 2 on an electrically conductive substrate comprising a titanium compound, a complexing agent, an accelerator, water and optionally organic solvents, buffering agents and one or more additives, characterized in that the titanium compound is titanyl sulfate and/or titanyl oxalate, the complexing agent is selected from the group consisting of citric acid, citrates, tartaric acid, tartrates, lactic acid, lactates, gluconic acid, gluconates, polyhydroxy-polycarbonic acids, ethylenediaminetetraacetate, methylglycinediacetate, iminodisuccinate, nitrilotriacetic acid and nitrilotriacetate, triethanolamine, phosphonic acid and phosphonates, polyaspartic acid and polyaspartates, polyacrylic acid and polyacrylates and the accelerator is selected from the group consisting of H 2 O 2 and organic peroxides. The invention further relates to a process for providing a corrosion-protective layer of TiO 2 on an electrically conductive substrate and to a metal substrate coated with a layer of TiO 2 .

1 . An electrodeposition material for the electrochemical deposition of a corrosion-protective layer of TiO 2  on an electrically conductive substrate comprising:
 a.) at least one titanium compound comprising titanyl sulfate and/or titanyl oxalate;   b.) a complexing agent selected from the group consisting of one or more of citric acid, citrates, tartaric acid, tartrates, lactic acid, lactates, gluconic acid, gluconates, polyhydroxy-polycarbonic acids, ethylenediaminetetraacetate, methylglycinediacetate, iminodisuccinate, nitrilotriacetic acid, nitrilotriacetate, triethanolamine, phosphonic acid, phosphonates, polyaspartic acid, polyaspartates, polyacrylic acid and polyacrylates;   c.) an accelerator selected from the group consisting of H 2 O 2  and organic peroxides;   d.) water; and   e.) optionally organic solvents, buffering agents and one or more additives.   
     
     
         2 . The electrodeposition material according to  claim 1 , comprising 0.05 to 0.3 mol/l titanium compound, 0.01 to 0.2 mol/l complexing agent and 0.02 to 0.2 mol/l accelerator. 
     
     
         3 . The electrodeposition material according to  claim 2 , wherein the electrodeposition material has a pH of 5 to 10. 
     
     
         4 . The electrodeposition material according to  claim 1 , comprising:
 a.) 0.05 to 0.3 mol/l titanyl oxalate;   b.) 0.01 to 0.2 mol/l complexing agent selected from one or more of citric acid, citrates, tartaric acid, tartrates, lactic acid, lactates, gluconic acid, and gluconates; and   c.) 0.02 to 0.2 mol/l accelerator.   
     
     
         5 . The electrodeposition material according to  claim 4 , wherein the electrodeposition material further comprises urea. 
     
     
         6 . The electrodeposition material according to  claim 1 , wherein the electrodeposition material has a pH of 6 to 9 and further comprises a polymeric cationic binder. 
     
     
         7 . The electrodeposition material according to  claim 6 , comprising the polymeric cationic binder in an amount of 5 to 60% by weight based on the total weight of the electrodeposition material. 
     
     
         8 . The electrodeposition material according to  claim 7 , wherein the polymeric cationic binder comprises at least one electrodepositable resin. 
     
     
         9 . The electrodeposition material according to  claim 8 , wherein the at least one electrodepositable resin is selected from amine salt group-containing resins, and quaternary ammonium salt group-containing resins. 
     
     
         10 . A process for providing a corrosion-protective layer of TiO 2  on an electrically conductive substrate comprising electrodepositing on an electrically conductive substrate a corrosion-protective layer of TiO 2  by contacting the electrically conductive substrate with the electrodeposition material according to  claim 1  at a current density of 0.01 to 100 mA/cm 2  and a temperature of 0 to 100° C., for 0.15 to 20 minutes. 
     
     
         11 . The process of  claim 10  wherein the electrodeposition material has a pH of 6 to 9 and further comprises a polymeric cationic binder. 
     
     
         12 . The process of  claim 10  wherein the electrodeposition material comprises:
 0.05 to 0.3 mol/l titanium compound;   0.01 to 0.2 mol/l complexing agent; and   0.02 to 0.2 mol/l accelerator.   
     
     
         13 . The process of  claim 10 , wherein the electroconductive substrate is selected from the group consisting of steel and aluminium. 
     
     
         14 . The process of  claim 13 , comprising the polymeric cationic binder in an amount of 5 to 60% by weight based on the total weight of the electrodeposition material. 
     
     
         15 . The process of  claim 12 , wherein the electrodepositing step is carried out by contacting the electrically conductive substrate with the electrodeposition material at a current density of 0.1 to 20 mA/cm 2  and a temperature of 20 to 60° C., for 0.5 to 10 minutes. 
     
     
         16 . The process according to  claim 15 , wherein the electroconductive substrate is selected from the group consisting of steel and aluminium. 
     
     
         17 . The process of  claim 10 , wherein the electrodeposition material comprises:
 a.) 0.05 to 0.3 mol/l titanyl oxalate;   b.) 0.01 to 0.2 mol/l complexing agent selected from one or more of citric acid, citrates, tartaric acid, tartrates, lactic acid, lactates, gluconic acid, and gluconates; and   c.) 0.02 to 0.2 mol/l accelerator.   
     
     
         18 . The process of  claim 10 , wherein the electrodeposition material further comprises urea. 
     
     
         19 . The process of  claim 10 , wherein the corrosion-protective layer of TiO 2  is deposited on the electrically conductive substrate such that said layer has a uniform layer thickness in the range of from 0.01 to 3.5 g/m 2 . 
     
     
         20 . A metal substrate coated with a layer of TiO 2  produced by the process of  claim 10 .