Chemistry: electrical and wave energy – Apparatus – Electrolytic
Reexamination Certificate
1997-10-20
2001-04-17
Bell, Bruce F. (Department: 1741)
Chemistry: electrical and wave energy
Apparatus
Electrolytic
C204S217000, C204S272000, C204S289000
Reexamination Certificate
active
06217725
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
This invention relates to electrochemical processing of the surfaces of metal substrates and the like to provide corrosion-resistant and decorative coatings from chemical treatment baths. More particularly, this invention relates to the so-called anodizing of metallic surfaces and more particularly to the use of a substantially solid flexible wiper blade during such anodizing.
(2) Prior Art
As detailed more particularly in U.S. application Ser. Nos. 08/179,520 filed Jan. 10, 1994 and 08/316,530, filed Sep. 30, 1994, the disclosures of which are hereby expressly incorporated into and made a part of this application, it has been found by the present inventors as well as others that a serious problem in electrolytic plating is the formation of bubbles of hydrogen on the surface of the material being coated and that it is conducive to good coating results to remove such hydrogen bubbles from a cathodic work surface. If nothing is done to remove the hydrogen from the coating surface during the coating process, coating will usually continue, but it may be seriously interfered with by the increasing size and number of bubbles. Likewise, in the anodizing of metallic surfaces in which the workpiece is made anodic and electrochemical oxygenation of the work surface creates a corrosion-resistant and/or decorative oxidized surface, the anodic workpiece tends to collect oxygen bubbles and the adjacent cathodes collect hydrogen bubbles that interfere with the electrochemical processing. Difficulty is also often encountered in anodizing with excessive heating of the solution layer next to the anode due to the high currents used in the process and the resistance of the dielectric metal oxide layer on the surface of the workpiece as such oxide layer thickens.
A second significant problem which has been long recognized in electrolytic coating baths is depletion of the electrolytic solution as coating progresses. The coating bath next to a workpiece may in particular become locally depleted of coating metal ions.
A further problem in the continuous coating of a flexible material such as sheet, strip and wire products is that the efficiency of electroplating usually increases as the spacing between the electrodes, one of which is the material to be coated, decreases. The same is true in anodizing. In other words, the efficiency of coating is usually inversely related to the spacing between the electrodes, one of which is the workpiece. However, due to the flexibility of the material being coated, it must, as a practical matter, be held away from the opposing electrode a sufficient distance to prevent arcing between the work material and the coating electrodes or anodes in the case of electroplating, or cathodes in the case of anodizing.
There has been a need, therefore, in the case of electroplating, for a means for removing hydrogen bubbles and cathodic film from a cathodic coating surface, preventing localized depletion of the coating bath with respect to coating material as well as allowing closer spacing of the coating electrodes and material being coated. The present applicants have found that a very effective means for accomplishing all three of these purposes is by the use of a relatively thin wiping blade in various embodiments applied to the surface of the workpiece at spaced intervals with a light contact. Such wiping blade deviates or strips away from the coating surface the relatively stable surface layer of electrolyte which tends to be drawn along with a moving cathodic surface, mixing and encouraging replenishing of the electrolyte next to the cathodic surface. Such blade at the same time wipes or sweeps away bubbles of hydrogen as well as encourages coalescence of small bubbles and films of hydrogen into large bubbles for subsequent wiping away. In addition, the wiping blade very effectively supports the material being coated, particularly in the case of relatively flexible material, such as light gauge thickness flat rolled sheet metal and prevents its deviation from its intended path and, therefore, allows closer spacing of the coating electrodes and the surface of the material being coated. The application of thin flexible wiping blades to the electroplating of metal substrates has been disclosed and claimed in applicants' prior applications noted above upon which this application is a continuation-in-part of a continuation-in-part and from which priority and continuity is claimed.
The present inventors have now found that some of the same benefits attained in electrocoating are likewise obtained in the process of anodizing if the discontinuous blades of the invention are used to prevent the accumulation of bubbles of oxygen on the anodic workpiece and also to decrease the heating of the solution next to the anodic workpiece while permitting closer spacing between the anodic workpiece and the cathodic electrodes. The flexible wiping blades of the invention also significantly reduce the power requirements of the process, other things being equal, by allowing closer approach of the workpiece and the adjacent electrodes. Some of the more pertinent prior art patents generally illustrating the history of the development of various solutions to some of the above-noted problems, particularly with respect to electrocoating, are U.S. Pat. Nos. 442,428 issued Dec. 9, 1890 to F. E. Elmore, 817,419 issued Apr. 10, 1906 to O. Dieffenbach, 850,912 issued Apr. 23, 1907 to T. A. Edison, 1,051,556 issued Jan. 28, 1913 to S. Consigliere, 1,236,438 issued Aug. 14, 1917 to N. Huggins, 1,473,060 issued Nov. 6, 1923 to E. N. Taylor, 1,494,152, issued May 13, 1924 to S. O. Cowper-Coles, 2,473,290 issued Jun. 14, 1949 to G. E. Millard, 3,183,176 issued May 11, 1965 to B. A. Schwartz, Jr, 3,715,299 issued Feb. 6, 1973 to R. Anderson et al., 3,751,346 issued Aug. 7, 1973 to M. P. Ellis et al., 3,772,164 issued Nov. 13, 1973 to M. P. Ellis et al., 3,886,053 issued May 27, 1975 to J. M. Leland, 4,125,447 issued Nov. 14, 1978 to K. R. Bachert, 4,176,015 issued Nov. 27, 1979 to S. Angelini, 4,210,497 issued Jul. 1, 1980 to K. R. Loqvist et al., 4,235,691 issued Nov. 25, 1980 to K. R. Loqvist, 4,399,019 issued Aug. 16, 1983 to W. A. Kruper et al., 4,595,464 issued Jun. 17, 1986 to J. E. Bacon et al., 4,853,099 issued Aug. 1, 1939 to G. W. Smith and 4,931,150 issued Jun. 5, 1990 to G. W. Smith. Some prior patents related to anodizing as well as some of the above problems are U.S. Pat. Nos. 3,074,857 issued Jan. 22, 1963 to D. Altenpohl, 3,650,910 issued Mar. 21, 1972 to G. W. Froman, 3,865,700 issued Feb. 11, 1975 to H. A. Fromson, 4,152,221 issued May 1, 1979 to F. G. Schaedel, U.S. Pat. No. 4,502,933 issued Mar. 5, 1985 to T. Mori et al. and 4,248,674 issued Feb. 3, 1981 to H. W. Leyh.
The following patents from the above compilation of patents are particularly illustrative of some of the more interesting disclosures of problems and solutions found in the above listed prior art.
U.S. Pat. No. 1,473,060, issued Nov. 6, 1923 to E. N. Taylor, discloses the use of a brush-type wiper in a coating tank environment to remove small gas bubbles and solid impurities from the coating surface intermittently (about 3 seconds out of every minute of coating) allowing the coating process to proceed uninterrupted during the time the brush is not operating.
U.S. Pat. No. 1,494,152, issued May 13, 1924 to S. O. Cowper-Coles, contains an early disclosure of a depleted layer of electrolyte carried around adjacent to the surface of a cathodic workpiece as well as bubbles of gas on the surface. The Cowper-Coles solution to these problems is to rapidly oscillate the cathodic workpiece to in effect shake off the bubbles and depletion layer (referred to by Cowper-Coles as the cathodic layer). The brushing takes place above the electrolyte surface as the hoop-type workpiece rotates into and out of the electrolyte.
U.S. Pat. No. 2,473,290 issued Jun. 14, 1949 to G. E. Millard discloses an electroplating apparatus for plating crankshafts and the like with chromium in which a
Anglen Marilyn Van
Forand James L.
Keeney Harold M.
Van Anglen Erik S.
Anglen Marilyn Van
Bell Bruce F.
Electroplating Technologies Ltd.
Wilkinson Charles A.
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