Electrolysis: processes – compositions used therein – and methods – Electrolytic erosion of a workpiece for shape or surface... – Agitation or vibration of electrolyte
Reexamination Certificate
2002-01-11
2003-06-17
King, Roy (Department: 1741)
Electrolysis: processes, compositions used therein, and methods
Electrolytic erosion of a workpiece for shape or surface...
Agitation or vibration of electrolyte
C205S674000, C205S675000, C205S676000, C205S677000, C205S680000, C205S684000
Reexamination Certificate
active
06579439
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to processes for electropolishing aluminum or aluminum alloy materials.
BACKGROUND OF THE INVENTION
In many aluminum polishing processes, the aluminum material is polished using a chemical process that does not require electricity to effectuate polishing. However, such polishing processes typically use high temperatures and may require the use of a scrubber to remove nitrous oxide fumes produced by the nitric acid and phosphoric acid components that can be used in such chemical process. Such processes can also be undesirable due to environmental concerns.
While processes using electricity, i.e., electropolishing processes, have been used to polish stainless steel metal surfaces, processes for electropolishing aluminum, in particular, aluminum alloy metal surfaces, have met with limited success due to the general requirement for hazardous or fume producing chemicals, the need for large amounts of electricity to be applied to effect the polishing or adverse effects on the metal surface caused by, for example, etching of the surface.
It would be desirable to have processes for electropolishing aluminum, in particular, aluminum alloy materials, that do not result in noxious and/or toxic fumes, use minimal electricity and do not etch the surface of the metal surface.
SUMMARY OF THE INVENTION
In accordance with the purposes of this invention, as embodied and broadly described herein, this invention, in one aspect, relates to processes for electropolishing aluminum, in particular, aluminum alloy metal surfaces, by immersing the metal surface in a polishing solution and making the aluminum alloy material anodic. The polishing solution can comprise a phosphoric acid solution and a hypophosphite-containing compound. The polishing solution can also comprise a polyol, a polyol ether and an organic acid.
Additional advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed.
DESCRIPTION OF THE INVENTION
The present invention may be understood more readily by reference to the following detailed description of particular aspects of the invention and the Example included therein.
Before the present compounds, compositions, articles, devices, and/or processes are disclosed and described, it is to be understood that this invention is not limited to specific methods or to particular reagents unless otherwise specified, and, as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.
As used in the specification and the appended claims, the singular forms “a,”“an” and “the” include plural referents unless the context clearly dictates otherwise.
Ranges may be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another embodiment. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.
A weight percent of a component, unless specifically stated to the contrary, is based on the weight of the formulation or composition in which the component is included.
“Optional” or “optionally” means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where said event or circumstance occurs and instances where it does not. For example, the phrase “optional steps in the process” means that additional step(s) may or may not be adopted and that the description includes processes where the optional step(s) is not included and processes where the optional step(s) is included.
Electropolishing is a method of polishing metal surfaces by applying an electric current through an electrolytic bath, as described, for example, in McGraw-Hill Encyclopedia of Science & Technology, pp. 810-811, 1982. The process is the reverse of electroplating. Anodic dissolution of surface features generally produces a flat, smooth, brilliant surface. One of ordinary skill in the art will recognize that the brilliance of the surface will be largely dependent on the use of the metal. For example, in some aspects, an electropolished surface may be matte or nearly matte; in other aspects, an electropolished surface may be “mirror-like.” In further aspects, an electropolished surface may have a brilliance between matte and mirror-like.
Current density on a metal surface can be an important parameter of electropolishing processes, including those disclosed herein. For example, below a certain voltage level, etching can occur; above the etching voltage level, a constant current region is reached where polishing can occur. At even higher voltages, oxygen evolution can interfere with polishing. The present invention applies particularly to electropolishing, but can also be applied to electrolytic etching or electrochemical removal by varying the operating parameters from the polishing region.
The term “aluminum alloy” is used herein to mean pure or substantially pure aluminum metal and alloys thereof in which the amount of aluminum is at least about 85%. Still further, the amount of aluminum in the alloy can be at least about 90% or, still further, at least about 95%. Aluminum alloys that can be electropolished according to the present invention can comprise about 85, 87.5, 90, 92.5, 95, 97.5 or 99% aluminum, where any of the stated values can comprise an upper or lower endpoint, as appropriate.
Aluminum alloys suitable for use in the present invention can contain less than about 2% silicon by weight, as measured by total weight of the aluminum alloy. Still further, the amount of silicon in the aluminum alloy can be less than about 1.5, 1.0, 0.5 or 0.1% by weight, as measured by total weight of the aluminum alloy.
Specific chemical compositions for aluminum alloys available commercially that are suitable for use herein are registered with the Aluminum Association, Inc., which reviews and assigns appropriate alloy designations to the set of chemical compositions. The Aluminum Association maintains registration records that list domestic and internationally registered chemical compositions of aluminum alloys and their corresponding alloy designations. Thus, those skilled in the art would be able to determine the composition of various aluminum alloys specified herein by their respective alloy designations. The records of the Aluminum Association that pertain to aluminum alloys suitable for use in the present invention are incorporated herein by this reference in their entireties. One such source of data is the publication “Aluminum Standards and Data,” which is published by the Aluminum Association.
Particular aluminum alloys that may be used in the present invention have Aluminum Association alloy designations in the 1000, 2000, 3000, 5000, 6000 and 7000 series. More specifically, suitable aluminum alloys include, but are not limited to, one or more of: 1050, 1060, 1100, 1145, 1175, 1200, 1230, 1235, 1345, 2024, 2219, 3003, 5252, 5657, 6063, 6061, 6463 and 7075.
In accordance with the present invention, an aluminum alloy may be fabricated into an aluminum alloy material prior to electropolishing. Aluminum alloy materials that can be used in the electropolishing processes of the present invention include, but are not limited to, a
King Roy
Needle & Rosenberg PC
Nicolas Wesley A.
Southern Industrial Chemicals, Inc.
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