Method for the fabrication of corrosion resistant electrodes
An electrode for use in instruments capable of measuring the electrophoretic mobility of particles in solution is disclosed. The electrode is comprised of an inexpensive support member, generally made of titanium, onto a flat surface of which has been connected, generally by microwelding, a flat electrically conductive but chemically inert foil member, preferably platinum. A uniform texture can be generated on the exposed surfaces of the electrode by various means including tumbling the electrode with an abrasive. An oxide layer can be generated on the support member by soaking the composite electrode in an appropriate medium, protecting the exposed surface of the support member from fluid contact with the sample solution, while the foil member, unaffected by the oxidation process, is able to contact the sample solution.
1. A method comprising:
providing an electrically conductive support member comprising at least one planar surface;
providing a flat, chemically inert, electrically conductive foil member;
welding the foil member to the conductive support member about the perimeter of the foil member, forming, thereby, a composite electrode, wherein the welding is performed by an electron beam;
etching an exposed surface of the foil member of the composite electrode so as to achieve a uniform, non-smooth surface there upon, wherein the etching comprises mechanically tumbling the composite electrode with an abrasive; and
in response to the etching, exposing the composite electrode to an oxidation agent, thereby causing an oxide layer to be formed upon an exposed surface of the support member.
2. The method of claim 1 wherein the foil member comprises platinum.
3. The method of claim 2 wherein the foil member is a disc of platinum foil.
4. The method of claim 3 further comprising milling an o-ring groove about a perimeter of the support member wherein the perimeter of the support member is chosen such that the perimeter does not intersect the planar surface to which the foil member is attached.
5. The method of claim 2 wherein the foil member is 100±5 μm thick, permitting thereby the foil member to be cleaned with mild abrasives without damage.
6. The method of claim 1 further comprising:
selecting the support member to be composed of a material or materials whose surface, when exposed to a strong oxidizer, causes an oxide layer to grow thereupon; and
selecting the foil member to be composed of a material or materials whose surface, when exposed to a strong oxidizer, resists an oxide layer forming thereupon.
7. The method of claim 1 wherein the oxidizing agent is a solution comprising hydrogen peroxide and water.
8. The method of claim 7 wherein the solution consists of 30% hydrogen peroxide and 70% water.
9. The method of claim 6 further comprising passing an electrical current through the composite electrode while the composite electrode is bathed in a salt solution, resulting in an oxide layer to form upon the support member of the composite electrode.