Apparatus and method for plating metallic strip

• US 4,367,125 A
• Filed: 12/18/1980
• Issued: 01/04/1983
• Est. Priority Date: 03/21/1979
• Status: Expired due to Fees

• Current Assignee: LTV Steel Company, Inc. (LTV Corp.)
• Original Assignee: Republic Steel Corp. (LTV Corp.)
• Inventors: Avellone, Richard C.
• Primary Examiner(s): Tufariello, T. M.
• Application Number:
  US06/217,806
• Time in Patent Office: 747 Days
• Field of Search: 204/15, 204/28, 204/206, 204/211
• US Class Current: 205/96
• CPC Class Codes: C25D 17/008 Current shielding devices
• CPC Class Codes: C25D 21/00 Processes for servicing or operating cells for electrolytic coating
• CPC Class Codes: C25D 21/04 Removal of gases or vapours ; Gas or pressure control
• CPC Class Codes: C25D 5/02 Electroplating of selected surface areas
• CPC Class Codes: C25D 5/06 Brush or pad plating
• CPC Class Codes: C25D 5/08 Electroplating with moving electrolyte e.g. jet electroplating using locally applied jets of electrolyte C25D5/026
• CPC Class Codes: C25D 7/0614 Strips or foils
• CPC Class Codes: C25D 7/0642 Anodes

Abstract

Method and apparatus for electrogalvanizing one or both sides of a steel workpiece are disclosed. A series of insoluble apertured plating anodes are positioned in spaced relation to the workpiece. When one side is to be plated one or more anodes are preferably mounted above the strip and when both sides are plated, anodes are mounted both above and below the strip. Solution is pumped through the holes in the anodes to momentarily contact the workpiece and they fall into a sump to be recirculated. A potential difference between the anode or anodes and the workpiece causes current flow through the electrolyte solution to electroplate the workpiece. Solution collected by the sump is directed to a reaction station for replenishment of the zinc metal ion. The solution is then filtered back to a main reservoir tank from which it is again pumped to the plating anodes.

Claims

1. A method for plating a surface of a metallic strip comprising the steps of:

(a) providing a source of electric potential difference between the strip and an electrode;

(b) substantially filling space between said surface and said electrode with sufficient plating solution to establish a current flow path between the electrode and the surface;

(c) providing a sump for receiving gravity flow of solution off the strip while maintaining separation of the workpiece and the solution in the sump; and

(d) shielding from solution impingement a portion of the strip side facing the electrode by use of shielding means separated from the strip and from the electrode.

2. The plating apparatus of claim 1 wherein the anodes are positioned both above and below the strip to plate both strip surfaces and wherein the strip path of travel in the vicinity of the anodes is inclined with respect to the horizontal.

3. A process of electroplating steel strip comprising the steps of:

(a) positioning a plating anode and a metal strip workpiece in closely spaced relationship to define a fluid flow path therebetween;

(b) flowing a liquid ion-containing plating solution toward the strip in sufficient volume to establish an electrical flow path from the anode to a facing surface of the workpiece with the electrical flow path being established across a portion of the surface and providing non-solution retaining shielding structure for facilitating substantially unrestricted gravity flow of said solution off the strip from along the sides of said strip while shielding a portion of the strip from direct solution impingement;

(c) establishing an electrical potential difference between the anode and the workpiece such that a flow of current causes ions in the plating solution to form a coating on the workpiece;

(d) collecting plating solution flowing from the fluid path at a location spaced from the strip;

(e) replenishing the ion concentration in the collected solution; and

,

(f) flowing the replenished solution along the fluid flow path.

4. Apparatus for plating a surface of a metallic strip comprising:

(a) means for providing a potential difference between the strip and an electrode;

(b) a sump;

(c) means for substantially filling space between said surface and said electrode with sufficient plating solution to establish a current flow path between the electrode and the surface without submerging the electrode or the strip in the sump and for allowing gravity flow of said solution off said strip surface into the sump; and

(d) insulative masking structure spaced from the workpiece and the electrode and interposed between the electrode and the sump.

7. The apparatus of claim 4 wherein the workpiece is a strip of steel and the source comprises a box-like anode insoluble in the solution with a planar surface defining holes therein confronting the strip and the apparatus further comprising means for pumping solution into the box-like anode and facilitating gravity flow of solution through the holes.

5. Apparatus for electroplating steel strip workpiece comprising:

(a) means for positioning one of a plurality of superimposed anodes and a steel workpiece in closely spaced non-submersed relationship to define a fluid flow path therebetween said one anode being substantially electrically isolated from other anodes;

(b) structure for flowing an ion-containing liquid plating solution along the path in sufficient volume to establish an electrical flow path from the anode to a surface of the workpiece and then to fall by gravity from the workpiece, with the electrical flow path being established across the surface;

(c) means for establishing an electrical potential difference between the anode and the workpiece such that a flow of current causes ions in the plating solution to form a coating on the workpiece.

6. The apparatus of claim 5 which further comprises structure for providing relative movement between the source and the workpiece and wherein the gravity flow is partially restricted to flow off said plating surface along a substantially non-obstructed escape path lateral to the direction of relative movement.

8. A method of electrogalvanizing one side of a steel strip comprising the steps of:

(a) preparing a liquid plating solution with zinc ion concentration for contacting the side;

(b) positioning in a non-submersed location a box-like anode insoluble in said solution above the strip;

said anode including a plurality of apertures spaced about a planar bottom surface;

(c) moving the steel strip under the anode with the one side parallel to and facing the planar anode surface;

(d) pumping the liquid solution into the box anode and allowing solution flow through the anode holes to the gap between anode and strip;

said apertures spaced to allow the solution to substantially fill the gap thereby providing an electrical current path between the anode and the one side;

(e) allowing substantially unrestricted solution flow off the strip to a sump positioned beneath the strip while shielding a portion of the strip by use of non-contacting masks spaced from both the anode and the strip;

(f) establishing an electrical potential difference between the anode and the strip to establish an electrical current flow along the electrical current flow path to provide a zinc coating to the one side;

(g) adjusting the plating rate and strip speed to achieve desired coating thickness along the one side of the strip;

(h) collecting solution in the sump and pumping it to a replenishing station and replenishing the zinc ion concentration in the solution; and

(i) recirculating replenished solution to the anode to recontact the one side of the strip.

9. Plating apparatus for electrogalvanizing one surface of steel strip as it moves past a plating station comprising:

(a) a supply of plating solution with zinc ions in solution;

(b) a box-like anode insoluble in said solution positioned in a non-submersed location above the strip with a planar bottom surface parallel to and confronting the strip;

said bottom surface defining a plurality of apertures;

(c) means for pumping solution into the anode under sufficient pressure to cause solution flow through the holes to contact the strip while maintaining an electrical flow path in said solution between the anode and the strip;

(d) a source of electrical energy coupled to both the anode and the strip to maintain the workpiece and the anode at different electrical potentials to produce a plating current to coat the strip;

(e) means for adjusting the distance between the strip and the anode to insure the plating solution substantially fills the gap between said anode and the strip; and

(f) means for collecting the solution as it flows off the strip and returning collected solution to the supply of plating solution, and

(g) shielding means spaced from the strip and anode and interposed between the anode and strip.

10. The apparatus of claim 9 wherein the means for adjusting comprises a guide roller which contacts a top surface of the strip and whose vertical position in relation to the anode is adjustable depending on the desired gap width between the anode and the strip.

11. A method for electroplating a generally flat metallic workpiece supported above the liquid level of a sump containing plating solution by use of a first generally flat electrode suspended above and parallel to the upper surface of the workpiece and by use of another electrode, said method comprising the steps of:

(a) substantially filling the space between the first electrode and workpiece surface with plating solution by causing downward impingement of plating solution on the upper surface of the workpiece;

(b) applying electrical potential between the first electrode and the workpiece to effect plating;

(c) at least partially shielding a portion of the workpiece surface from direct solution impingement thereon without contacting the workpiece by use of masking structure between the first electrode and the workpiece surface, said masking contacting neither the strip nor an electrode, while avoiding retention in the masking structure of substantial amounts of plating solution; and

(d) substantially preventing electric current flow between the first electrode and said another electrode.

12. A system for electroplating a metallic workpiece having a generally flat surface, said system comprising:

(a) a sump for containing plating solution;

(b) means for supporting the workpiece spaced above a level of solution in the sump;

(c) an electrode having a generally flat surface positioned proximate and facing a workpiece surface and being generally parallel thereto;

(d) apparatus for substantially filling the space between the workpiece surface and electrode surface with plating solution;

(e) electrical means for applying an electrical potential difference between the workpiece and the electrode for effecting plating, and

(f) structure associated with the electrode and the workpiece supporting means for adjustably varying inclination of the workpiece surface and electrode surface from the horizontal.

13. A method for electroplating a metallic workpiece supported above the liquid level of a sump containing plating solution by use of an electrode having a generally flat bottom surface suspended above the upper surface of the workpiece, said method comprising the steps of:

(a) substantially filling the space between the electrode and workpiece surface with plating solution by causing impingement of plating solution on the upper workpiece surface;

(b) applying electrical potential between the electrode and the workpiece to effect plating; and

(c) at least partially shielding a portion of the workpiece surface from direct solution impingement thereon without contacting the workpiece itself by the use of masking structure locatable between and not contacting the electrode and the upper workpiece surface while avoiding retention in the masking structure of plating solution.