US 3445371 A
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May 20, 1969 s. s. JOHNSTON ANODE STRUCTURE FOR CONTINUOUS STRIP ELEGTROPLATING File d June 15, 1966 f M x 7 a M m s. M m w M A S m 3 g M H 2 NQ i 2 Y B a 2: mm
.m n A mm WWI i Q m w r m 0. 0 o 0 O 0 o s o r o o o o 3 o o 3 ATTORNEYS United States Patent 3,445,371 ANODE STRUCTURE FOR CONTINUOUS STRIP ELECTROPLATING Samuel S. Johnston, Steubenville, Ohio, assignor to National Steel Corporation, a corporation of Delaware Filed June 15, 1966, Ser. No. 557,830 Int. Cl. C23b /68; B01k 3/00 US. Cl. 204-206 5 Claims This invention is concerned with continuous strip electroplating apparatus and, its more specific aspects, with anode structure forming part of the plating cells used in continuous-strip electroplating apparatus.
The invention is used with continuous-strip electroplating lines which are known in the art and are described in US. patents such as, Rieger et al., #2,399,254, Kompart, #2,6l0,146, and Wilson, #2,453,48l. In operation, continuous strip travels longitdinally through a plurality of plating cells while immersed at bath surface level in plating solution with one surface of the strip facing plating metal. Electrically the strip is connected as a cathode and the plating metal as an anode and the electroplating process is continuous as the strip travels successively from one plating cell to the next.
Uniform spacing between the strip and the plating metal in each plating cell is desired in order to have uniform coating across the full width of the strip. As disclosed in the above-mentioned patents, this is accomplished by providing plating metal in the form of individual anode bars which are supported on a plane which is inclined with respect to the plane of traveling strip.
In the past the anode bars have been supported near one longitudinal end by a member supplying current to the anode bars and near their opposite longitudinal ends by electrically insulated guide members. Ordinarily a plating cell contained two banks of anode bars with the member supplying current being centrally located in the plating cell and electrically insulated guide members being located at opposite longitudinal ends of the plating cell.
Such anode support structure has a number of dis advantages. For example, the centrally-located, currentsupply member has a useful life of only from two to four months. A number of factors contribute to this short life, for one, as the anode bars erode, the upper surface of the current-supplying member is exposed to and eroded by plating solution. Further, it is difficult to move anode bars uniformly across a cell because of the difference in coefficients of friction of support structure at opposite longitudinal ends of the anode bars. Also, current is not distributed uniformly causing uneven end erosion of anode bars which increases exposure of plating cell electrodes as the anode bars are moved across the plating cells.
The main objective of the present invention is to overcome these disadvantages and resultant problems of the prior art anode structure.
The accompanying figures will be referred to during a detailed description of the invention. In these figures:
FIGURE 1 is a schematic view of a plating cell embodying the invention.
FIGURE 2 is a sectional view taken along the lines 2-2 and FIGURE 1 With an added shunt connection not shown in FIGURE 1, and
FIGURE 3 is a sectional view of a portion of FIG- URE 2 taken along the lines 3-3.
The apparatus of FIGURES 1 through 3 is used in a continuous-strip electrotinplating line of the Halogen type, however, the invention can be used for continuousstrip electrozinc-plating or for other continuous-strip electroplating operations.
Referring to FIGURE 1, continuous strip 8 moves 3,445,371 Patented May 20, 1969 ice of cell 11 strip 8 travels between metal cont-act roll 14 and backup roll 15. At the exit end strip 8 travels between metal contact roll 16 and backup roll 17. Plating metal is provided from a plurality of anode bars such as 20 and 22. Current is supplied at anode terminals 24,
- 26, 28, and 30. In the electrical circuit the strip acts as a cathode and the electrical circuit is completed through metal contact rolls 14 and 16.
Anode support members 32, 34, 36, and 38 provide an inclined plane of support for individual anode bars. This can be best seen in the side view of anode support member 34 of FIG. 2.
As individual anode bars erode they are moved from left to right, with new bars being added at the left and eroded bars being removed at the right. A substantially uniform predetermined space 39 is maintained between the anode bars and strip 8.
Referring to FIGURE 3, anode bar support member 34 includes an electrode member 40 and a metallic base member 42. The upper member 40 is ordinarily a carbon electrode and the base member is generally formed from the metal being plated. Electrode 40 is held to base member 42 by a plurality of bolts, such as 44, ends of which are recessed as shown. The recess cavities 46 and 48 are filled with carbon cement. The sidewalls and bottom portion of the anode support member are covered with an electrically insulating protective layer 50, such as rubber.
As shown in FIG. 1, the bottom surfaces of individual anode bars completely overlay the upper contact surfaces of anode bar support members and extend beyond the support members. In this way, as metal from the anode bars goes into solution, the upper contact surfaces of anode bar support members is protected from plating solution by the anode bars. Contact surfaces between anode bars and electrode members can have planar or other interfitting configurations to insure intimate contact between the anode bars and the electrodes for purposes of good electrical contact, to provide protection against erosion for the electrodes, and to serve as guide means for moving bars squarely across the bath. It should be noted that sufiicient anode bar overhang is provided so that erosion of bar ends during movement across the entire bath can occur without exposure of the upper surfaces of the electrodes.
It should also be noted that the anode bars are supported at both longitudinal ends by current carrying electrode surfaces so that the coeflicient of friction is substantially the same at both ends of the bars facilitating even movement of the bars across the bath. Another advantage of this type of support is that plating current is more evenly distributed over the entire longitudinal lengths of the anode bars so that the anode bars erode uniformly at both ends and substantially uniformly along their full lengths. In addition, overheating of plating cell anode terminals is avoided by distribution of current; 6.2. the single anode terminal of prior art continuous-strip electrotinplating cells carries 10,000 amperes, whereas in the present embodiment each anode terminal carries 2,500 amperes.
Measurements of electrode wear indicate that these members may last from a year to fifteen months as compared to the two to four month life of prior art structure.
In practice the anode support members shown are arranged in a cell so that their upper contact surfaces lie in the same plane. In order to avoid disrupting this alignment, when connecting an anode terminal to a current supply means, the invention teaches use of a flexible shunt. As shown in FIGURE 2, flexible shunt 52 con nects anode terminal 26 to current supply bus bar 54; it is understood that similar flexible shunts are connected at each terminal in practice. Flexible shunts can be of braided construction, foil construction, or other suitably flexible construction which avoid dislocation of the anode bar support members when connecting an anode terminal to a bus bar.
Other advantages of the present invention will be apparent to those skilled in the art. It is understood that other materials and shapes can be substituted for those disclosed in the above embodiments While still relying on the teachings of the present invention so that the scope of the invention is to be determined from the attendant claims.
1. In a plating cell for continuous strip electroplating in which metallic strip travels longitudinally through a plurality of plating cells with a bottom surface of the strip immersed in plating solution and in predetermined spaced relationship with a plating metal source, anode structure comprising a plurality of elongated anode bars, and
a plurality of anode bar support members, the support members being elongated and extending lengthwise in a direction transverse to strip travel and being spaced from each other along the direction of strip travel,
each anode bar support member presenting an upper surface for carrying plating current,
the individual anode bars being arranged in side-byside relationship and extending lengthwise in the direction of the strip travel between spaced anode bar support members with bottom surface portions being in current conducting relationship with the upper surfaces of the support members and covering the upper surfaces of the support members.
2. The structure of claim 1 in which each plating cell includes two pair of anode bar support members, each pair of anode bar support members supports a bank of individual anode bars, and each anode bar support member includes means for supplying plating current through the anode bar support member.
3. The structure of claim 2 in which the means for supplying plating current to each anode bar support member is connected through a flexible current conducting means to a current supply means.
4. The structure of claim 2 in which the anode bar support members comprise a metallic base member, a carbon electrode secured to the metallic base, and electrical insulation means covering portions of the metallic base member and carbon electrode to prevent exposure to plating solution.
5. The structure of claim 1 in which bottom surface portions near longitudinal ends of the elongated anode bars and upper surfaces of the anode bar support members have planar configurations.
References Cited UNITED STATES PATENTS 2,399,254 4/1946 Rieger et al. 204-206 2,610,146 9/1952 Kompart 204206 2,690,424 9/1954 Hassell 204-206 HOWARD S. WILLIAMS, Primary Examiner.
T. TUFARIELLO, Assistant Examiner.
US. Cl. X.R.
Citations de brevets