Electropolishing process for titanium

Abstract

The present invention relates to a method of electrochemical polishing of surfaces of titanium or titanium-containing alloys, such as Nitinol. An electrolyte is used that comprises methanesulfonic acid and one or more alkanediphosphonic acids. These alkanediphosphonic acids can optionally be substituted with hydroxy and / or amino groups. A further aspect of the present invention relates to the use of said electrolyte for the electropolishing of titanium or titanium-containing alloys.

Description

[0001]The present invention relates to a method of electrochemical polishing of surfaces of titanium or titanium-containing alloys. This method is especially suitable for alloys that have a titanium content of at least about 50 mol. %, for example the nickel-titanium alloy Nitinol. For this, an electrolyte is used that comprises methanesulfonic acid and one or more, optionally substituted alkanediphosphonic acids. The present invention also relates to the use of said electrolyte for the electropolishing of surfaces of titanium and / or titanium-containing alloys, such as Nitinol.BACKGROUND OF THE INVENTION[0002]Electrochemical polishing or electropolishing, as well as the brightening and deburring of metal surfaces, is a process that is frequently employed in industry for treatment of the surfaces of metal workpieces and objects. This treatment is used for improving surface quality, for example by removing burrs from edges and surfaces, by smoothing, cleaning and brightening, both for...

AI Technical Summary

Problems solved by technology

All of these electrolytes are indeed capable of achieving satisfactory electropolishing results on surfaces of pure titanium and a selection of titanium alloys, but they are only partially able to produce a satisfactory quality of electropolishing of Nitinol, a nickel-titanium alloy, which consists of about 50 mol.

Furthermore, all of these electrolytes have the disadvantage that their use involves substantial technical and health risks.

Thus, for the electrolyte mixture according to No. 1 there is a risk of explosion if it is handled incorrectly, whereas the other electrolytes pose a considerable health risk, in particular because of their content of fluorides.

The use of these electrolytes, and processes in which these electrolytes are used, in an industrial context requires expensive equipment and precautions for maintaining the process parameters, and for protection of labor and of the environment.

Generally the execution of these electropolishing processes additionally requires an expensive cooling system, so that the generally very low working temperatures can be maintained and, when using fluoride-containing electrolytes, enclosure of the electropolishing plant, and exhaust air purification.

Apart from the health risk through the apparently preferred use of methanol and the associated formation of highly toxic, carcinogenic dimethylsulfate during the process, this method has the further disadvantage that because this electrolyte is highly flammable, expensive cooling of the electrolyte to temperatures below 15° C. is necessary, together with automatic extinguishers for fire protection.