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 TiO2 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 H2O2 and organic peroxides. The invention further relates to a process for providing a corrosion-protective layer of TiO2 on an electrically conductive substrate and to a metal substrate coated with a layer of TiO2.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a continuation under 35 U.S.C. § 365(c) and 35 U.S.C. § 120 of international application PCT / EP2006 / 005790, filed 16 Jun. 2006, and published 28 Dec. 2006 in English as WO 2006 / 136333, which is incorporated herein by reference in its entirety. This application also claims priority under 35 U.S.C. § 119 of EP 05013424.6 filed 22 Jun. 2005, which is incorporated herein by reference in its entirety.FIELD OF THE INVENTION[0002]The present invention relates to an electrodeposition material for the electrochemical deposition of a corrosion-protective layer of TiO2 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. Such TiO2 layer deposited electrochemically may serve as an appropriate primer layer for subsequent coating treatment (e.g. coating with organic materials, such as for instance...

AI Technical Summary

Benefits of technology

[0012]It is an object of the present invention to provide further electrodeposition materials for the electrochemical deposition of a corrosion-protective layer of TiO2 on an electrically conductive substrate which result in TiO2 layers providing excellent corrosion protection and which may serve as an excellent primer layer for subsequent coating treatment. Surprisingly this object can be achieved by the use of titanyl sulfate and / or titanyl oxalate as the titanium component combined with a special combination of complexing agents and accelerators.

Problems solved by technology

Technically simpler to perform, but less effective, is the simple application of a primer coat to a metal prior to lacquer-coating thereof.

For example, chromating processes are disadvantageous from both an environmental and an economic point of view owing to the toxic properties of the chromium and the occurrence of highly toxic sludge.

However, chromium-free wet processes, such as phosphating, as a rule, also result in the production of sludge containing heavy metals, which has to be disposed of at some expense.

Another disadvantage of conventional wet coating processes is that the actual coating stage frequently has to be preceded or followed by further stages, thereby increasing the amount of space required for the treatment line and the consumption of chemicals.

Although dry coating processes entail fewer waste problems, they have the disadvantage of being technically complex to perform (for example requiring a vacuum) or of having high energy requirements.

The high operating costs of these processes are therefore a consequence principally of plant costs and energy consumption.

The article investigates above all the influence of deposition conditions on the morphology of the oxide layers; it does not disclose any practical application of the layers.