US2399964A

US2399964A - Method of electrogalvanizing

Info

Publication number: US2399964A
Application number: US443264A
Authority: US
Inventors: Clemson H Ward
Original assignee: Bethlehem Steel Corp
Current assignee: Bethlehem Steel Corp
Priority date: 1940-03-11
Filing date: 1942-05-16
Publication date: 1946-05-07
Anticipated expiration: 1963-05-07

Description

M y 7, 1946. c. H. WARD 2,399,964

I METHOD OF ELECTED-GALVANIZING Original Filed March 11, 1940 2 31 1 1 awe/whom 554 yawn-01211 W a! y 9 6- v C. H. WARD 2,399,964. I METHOD OF ELECTED-GALVANIZING Original Filed Mafch 11, 1940 2 Sheets-$1 691; 2

Glamor/ 12 iI Znrd.

Patented May 7, 1946 ME'rnon F ELECTROGALVANIZING Clemson H. Ward, Baltimore, Md., assignor to Bethlehem Steel Company, a. corporation of Pennsylvania Original application March 11, 1940, Serial No. 323,300. Divided and this application May 16, 1942, Serial No. 443,264

7 Claims.

This invention relates to a method for treating fiat rolled metal products, sheets, strip or plates in one or more liquid baths in which said flat rolled products disposed in a vertical plane are passed horizontally through cells or tanks containing the treating liquid, and is a division of my copending applications Serial Nos. 323,300 and 383,135, filed March 11, 1940, and March 6, 1941, respectively. The former has matured into Patent No. 2,384,660 of September 1 945.

In particular the invention relates to a method for electroplating flat rolled products in which said products are passed, without deviating from a vertical plane, through a succession of cells or enclosures slightly deplating, rinsing, drying and other operations are performed upon same.

One of the objects of my invention relates to the method of coating 2. sheet of metal with zinc by electrodeposition, which comprises subjecting the sheet as an anode to the action of an electric current in the presence of an electrolyte to clean the sheet, then subjecting the sheet as a cathode in the presence of an electrolyte for zinc plating in a cell-or aplurality of cells each having an individual electric circuit connection on each side of each cell, and finally subjecting the plated sheet as an anode to the action of an electric current in the presence of an electrolyte to slightly deplate the coating on the sheet.

This electrolyte consists of an aqueous solution of zinc sulphate and sulphuric acid.

Another object of my invention relates to the method of treating the coating after the plating operation to produce a uniform bright finish or polished surface.

Other objects will appear hereinafter.

Having thus given a general description of the objects of my invention, I will now in order to make the same more clear, refer to the annexed two sheets of drawings forming a part of .this specification and in which like characters of reference indicate like parts.

Figure 1 is a diagrammatic view in side elevation of my improved galvanizing plant illustrating, the general arrangement of the complete apparatus for plating sheets; and

Figs. 2 and 3 show longitudinal transverse sections of the feeding in and discharge ends of the plant, respectively, taken on the line 33 of Fig. 1.

Referring now-to the various characters of reference on the drawings, the numeral I designates the base member having. a strip of insulation 2 thereon upon which the cells and roll boxes are in which cleaning, electroplating,-

mounted and assembled together in longitudinal alignment above the launder 3 extending under the apparatus for receiving the waste water discharged therefrom. Adjacent to the launder 3 and on the same level are the launders l and 5 for receiving the electrolytes from the plating and first anodic cell l2, respectively, from which each are returned to a sump (not shown) where his cooled and the electrolytes recirculated.

The sheet 6 to be plated is disposed in a vertical position between pairs of side rods 1. with its lower edge engaging grooved rollers 8 of a feed table 9, and advanced manually, or in any approved manner into the electrolytic galvanizing plant from the right hand end of the apparatus as indicated in Figure 1, where it first passes between a pair of contact rolls In in the roll box ll then into the pickling bath in the anodic cell [2, where the surface of the sheet is thoroughly cleaned and freed from rust, scale; oil, grease, etc. In the anodic cell l2 the polarity of the electric circuit is reversed to that of the plating cells and the sheet forms the anode, and the lead inner lining of the cell the cathode as it passes through the path in this cell. The sheet is then advanced between a pair of rubber-covered squeegee or sealing rolls I3 in roll box It and then is advanced between another pair of squeegee rolls Is in the roll box It, which guides the advancing end of the sheet into the first of a series of plating cells,

of which seven are shown for illustration numbered n, l8, I9. 20, 2|, 22 and 23, but a greater or less number of plating cells may be used if desired. As shown in Figure 1, each plating cell has at its left hand end a contact roll box indicated as 24, 25, 26, 21, 28, 29 and 30, respectively in each of which is mounted a pair of .lead covered contact rolls 3|, between which the sheet being plated is passed. After passing through the plating cells and between the pairs of contact rolls in sequence it is then fed into an anodic cell 32 and between a pair of contact rolls 33 in roll box 34 in which the polarity of the electric circuit is reversed to that of the plating cells. In thi case the sheet would again form the anode and the lead lining of the cell the cathode, the positive side 35 of the circuit extending to the contact rolls and the negative side of the circuit 36 to the side of the cell. In this manner the surface of the coating is slightly deplated thereby producing a uniformly bright finish or polished surface. After passing through the anodic cell 32 and between the contact rolls 33 in roll box 34 it is then fed into roll box 31 between a pair of squeegee rolls 38 which retain the electrolyte in the roll box 34 and then advanced between another pair of squeegee rolls to inroll box 40. thence into a wash box ll havlng perforated Plo 42 for spraying water on each side of the sheet then into a drying box 43 having perforated steam pipes It for heating the sheet and finally the sheet passes between another pair otsqueegeerolls llinarollbox 46 firwipingthe surface of the sheet from which point it is ejected onto a receiving table 4! which is constructed in a similar manner as the feed table. having the vertical pairs of guide rods 1 and rollers 8.

The cell roll boxes are secured together by means of U-shaped clamps It and the ends of the units are insulated from each other by means of panels ll forming gaskets between the same. Each panel is provided with a central reinforcing late it of steel to prevent warping which is covered with insulating material such as rubber or the like. These panels ll have a vertical central slot formed therein as at II for the sheet to pass through. The panels also have attached thereto adjacent to the slots porcelain guides 52 for guiding the sheet into or out of the different units and the input and output sealing flaps 53 and 54 respectively.

The plating cells are-provided with a pipe 55 adapted to supply electrolyte thereto and pipes 56 for receiving the overflow of the electrolyte from the plating cells and conveying it to the launder 4, and thence to a sump. The anodic cell 12 is also provided with a pipe 51 for supplying a pickling bath thereto and overflow pipes 58 for conveying the pickling bath to the launder 5.

In the anodic cell 32 the same electrolyte may be used as that for the plating cells and Willieceive itssupply in a similar manner through the pipe 59 and the overflow will be received by pipes 60 and returned to the launder 4.

As indicated in Figure l the contact and squeegee rolls are rotated by means of a motor GI and driving mechanism which is more clearly illustrated and described in my copending application Serial No. 323,300.

When necessary to cool the cell wall electrodes the cells may be water jacketed as shown in cell l2.

This is particularly desirable when the cell walls are used as cathodes in an anodic treatment of the work since in this case a large portion of the ohmic heating of the solution occurs in the hydrogen gas layer at the cathode. To remove this heat with maximum efliciency the cell may be provided with a water jacket 62 formed by having a plate 63 secured to the lining 64 by means of studs 65. The jackets thus formed are supplied with inlet and outlet pipes 66 and 61 respectively.

In order to secure substantially uniform electrolytic action on each side of the work as it passes through the cells it is necessary to hold the work in uniform spaced relation with the electrodes or sides of the cells. This is accomplished by securing a plurality of porcelain guides 68 of frusto-conical shape to the inner sides of the lead lining of the cells. Each guide on one side of the cell is in transverse alignment with the opposite side of the cell. These frusto-conical guides have their inner surfaces far enough apart to allow the sheet 6 to pass freely between them and are so disposed that the shielding effect will be as uniformly distributed as possible.

Referring to Figure 1 it will be noted that the motor generator 69 furnishes the current through the bus bars and H and terminal connections to the contact rolls and plating cells on one side ascacoa of the apparatus, the negative side of the circuit extending to the contact rolls, while the position side of the circuit is connected to one side of the plating cells, and the motor generator 12 supplies the current through the bus bars 13 and 14 and terminal connections in a similar manner to the contact rolls and plating cells on the opposite side of the apparatus. With this system of connections and with opposite sides of the cells insulated from each other it is possible to vary the electrolytic effect on either side of the-work by varying the current output of the two generators.

A more usual system of connections to a plurality of cellsis to connect both sides of each-cell to one generator, and, in case a plurality of generators are to be used to connect each generator to a cell or group of cells in succession through the apparatus.

The polarity for the anodic cells I! and 32 is reversed to. that of the plating cells. In these two cells the positive side of the circuit 35 from the motor generator 15 is connected to both pairs of contact rolls Ill and 33, while the negative side 38 is connected to both sides of each cell. In this manner of connecting up the circuit the work or sheet 6 will be the anode andthe lead lining of the cell the cathode.

electrolytically upon the sheet or strip is of dull appearance and of relatively rough texture. It may also be discolored by oxidation after emerging from the plating bath or by chemical attack of the electrolyte upon it. In addition to washing the work at the exit end of the plating apparatus as elsewhere described, I apply one or more electro-chemical treatments to the work in a cell or cells located adjacent to the plating cells at the exit end of the apparatus by reversing the polarity in which the electro-deposited coating is acted upon anodically in the plating electrolyte as indicated in Figure 1, or I may use a. separate electrolyte and electric circuit connections for the purpose for brightening or smoothing the surface of the coating by partially deplating the work.

Although I have shown and described my invention in considerable detail, I do not wish to be limited to the exact and specific details shown and described, but may use such substitutions, modifications or equivalents thereof as are embraced within the scope of my invention or as pointed out in the claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. The method of. coatlng and polishing a sheet of ferrous'metal with zinc by electrodeposition in a continuously progressing operation, which comprises subjecting the sheet as an anode to the action of an electric current in the presence of an electrolyte to clean the sheet, then subjecting the sheet as a cathode to the action of an electric current in a cell containing an electrolyte consisting essentially of zinc sulphate and sulphuric acid dissolved in water having an electric the coating on the plated sheet.

2. The method of coating and polishing a sheet of ferrous metal with zinc by electrodeposition in a continuously progressing operation, which conasoaoei sists in subjecting the sheet as an anode to the action'of an electric current in the presence of an electrolyte to clean the sheet, subjecting the sheet continuously submerged as a cathode to the action of an electric current in a plurality of cells containing an electrolyte consisting essentially of zinc sulphate and sulphuric acid dissolved in water in succession each having an individual electric current connection on each side of the cell to plate the sheet, and finally polishing the zinc coating by subjecting the sheet as an anode without access to the air after the plating operation to the action of an electric current in the presence of the same electrolyte used for zinc plating to slightly deplete the coating on the plated-sheet.

3. The method of coating and polishing a sheet of metal with zinc by electrodeposition in a continuously progressing operation, which comprises continuously subjecting portions of the sheet as an anode to the action or an electric current in the presence of an electrolyte to clean the sheet, then subjecting the clean portions. of the sheet as a cathode to the action of an electric current in the presence of an electrolyte consisting of an aqueous solution 01' zinc sulphate and sulphuricacid for zinc plating, and finally polishing the zinc coating by again reversing the polarity of the sheet and subjectingthe plated portions of the sheet as an anode while still submerged to an electric current in the same electrolyte used for zinc plating to slightly deplate the coating on the sheet.

4. The method of polishing a zinc coating which has been produced by electrodeposit on a sheet or metal, consisting of subjecting the c plated sheet immediately after the plating operation and while still submerged in the electrolyte as an anode to the action of an electric current in the presence or the same electrolyte consisting or an aqueous solution of zinc sulphate and sulphuric acid similar to that used in coating without access to the air between the two opera.-

tions to slightly deplate the coating on the plated 5. The method of coating and polishing a sheet of metal by electrodeposition progressively by advancing the sheet through a plurality of cells each containing an electrolyte and having an electric circuit, which consists in first subjecting the sheet as ananode in a bath to clean the sheet,

then conducting the sheet through a plurality of cells continuously submerged in an electrolyte consisting of an aqueous solution of zinc sulphate and sulphuric acid as a cathode to plate the sheet, and finally polishing the zinc coating by passing the sheet while still submerged through the same electrolyte used for zinc plating as an anode to slightly deplate the coating-on the sheet.

6. The method of coating and treating a sheet of metal progressively by electrodeposition, which consists in advancing the sheet through a pickling bath as an anode to clean the sheet, thence into a plating bath consisting of an aqueous solution of zinc sulphate and sulphuric acid in a cell as a cathode to plate the sheet, and finally polishing the zinc coating while still submerged by advancing the plated sheet into a cell communicating with the plating cell containing the same electrolyte used for zinc plating as an anode to slightly deplate the surface of the coating on the sheet.

7. The method of coating and treating a sheet of metal or the like progressively by electrodeposition, which comprises subjecting the sheet as an anode to the action or an electric current in the presence or an electrolyte to clean the surface or the sheet, then subjecting the sheet as a cathode to the action of an electric current in the. presence or a plating bath consisting of an aqueous solution of zinc sulphate and sulphuric acid to plate the sheet, and finally polishing the zinc coating while still submerged by again reversing