US1918159A - Electrodeposition - Google Patents

Description

Patented July 11, 1933 UNITED STATES PATENT OFFICE LOUIS EISBERG AND WILLARD Is. GREENWALD, OF NEW YORK, N. Y., ASSIGNORS TO WEISBERG & GREENWALD, INCL, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK ELECTRODEPOSITION No Drawing.

This invention relates to electrodeposition, and particularly to the preparation of surfaces of lead or lead-containing alloys to receive electrodeposited coatings of metal.

Lead and lead alloys such as type metal 1 and similar metals which are relatively soft are easily abraded, and consequently the exposed surfaces, when subjected to wear, are rapidly destroyed. This is particularly true in the case of stereotype plates and linotype slugs which are made by casting a molten alloy of lead containing small amounts of hardening agents such as antimony. Printing surfaces of lead and lead alloys wear rapidly and are not adapted,.therefore, for the successful printing of large editions.

Attempts have been made heretofore to deposit wear-resisting metals electrolytically upon surfaces of lead and lead alloys, but it is diflicult to secure a proper bond between the electrodeposited metal and the underly-. ing surface. Usually the coating metal cracks and chips from the surface and consequently the object of applying the coating metal cannot be accomplished successfully.

It is the object ofthe present invention to provide a simple and efiective procedure whereby wear-resisting metals can be deposited in a satisfactory manner upon the surface of soft metals such as lead and alloys thereof to produce wear-resisting coatings which adhere to the underlying metal.

Another object of the invention is the provision of a method for depositing metals such as copper,.brass, nickel, or successive coatings of these metals upon printing plates and slugs and other similar objects of lead or lead-containing metals.

The object of the invention is accomplished by suitably cleaning the surface of the article to be coated and then subjecting it as the anode for a short time to electrolysis in av neutral or alkaline solution. It is essential to the invention that the electrolyte employed in the anodic treatment be slightly alkaline or neutral, since acid solutions tend to cause the formation of lead peroxide on a surface of lead or lead-containing alloy. After the brief anodic treatment, the surface can be coated with copper, brass, or nickel or with Application filed January 19, 1932. Serial No. 587,606.

any of these metals successively by exposing it as the cathode in a suitable electrolyte under the usual conditions required for the deposition of the metals.

The invention will be described particularly with reference to the treatment of stereotype plates, although the procedure may 'be employed for the preparation for and depcleaner solution, the plate being connected as the cathode with a voltage of approximately 6 volts. The composition of the electric cleaner solution may vary. It should, however, be an alkaline solution strong enough to remove grease and ink, if necessary. A solution containing 50 grams of trisodium phosphate per liter is satisfactory unless the plate is very dirty, in which case a stronger solution may be employed. After the plate has been cleaned by exposure in the electric cleaner solution for a suflicient period, which will vary depending upon the amount of dirt to be removed, it is brushed, if necessary, and is then rinsed in running water.

The plate is then connected as the anode in a suitable solution slightly alkaline or neutral. A satisfactory solution for this purpose contains approxlmately 50 grams per liter of sodium acetate. The plate is electrolyzed With a voltage of approximately 6 volts for a brief period, for example about 30 seconds, at ordinary room temperature. lt is then removed from the bath and is ready for the plating operation.

Although we prefer to use a solution of sodium acetate as the electrolyte for the anodic treatment, it is possible to secure satisfactory results with various neutral and alkaline solutions which do not form insoluble lead compounds. Solutions of the acetates citrates and chlorides of the alkali metals are especially suitable for this treat- 5 ment.

The plating procedure will vary depending upon the metal or metals to be deposited. For example, in plating with cop er, we may employ the procedure su geste in Principles of Electroplatin and Electroforming by Blum and Hoga 00m, second edition, page 228, employing a solution of copper (cuprous) cyanide about 22.5 grams per liter, sodium cyanide about 34.0 grams per liter, and sodium carbonate about 15.Q, grams per liter. The electrolysis may be conducted at a temperature of ap roximately 4Q C. and a current density of about 14 amperes per square foot and for a time suflicient to deposit-the desired amount of cop er.

For brassplating, we may emp oy the procedure as set forth by Blum and Hogaboom at pages 379to1389. Thus we may use a cyanide solution containing copper and zinc in the ratio of 80:20 with a total metal content of at least 22.5 grams per liter and a free cyanide content about one-fourth the total of combined cyanide. To this bath may be added 30 to 60 grams per liter of sodium carbonate. In this electrolyte at a temperature of about 40 C. the surface to be coated may be disposed as the cathode and subjected to the electric current with a cathode current density of about 2.8 amperes persquare foot. After a suitable interval which is best determined by consideration of the amount of brass to be deposited on the surface, the cathode is removed and is again thoroughly cleaned.

For nickel plating we may use a nickel solution as described by Blum and Hoga boom, page 260, solution 3, containing nickel sulphate about 200 grams per liter, nickel chloride about grams per liter, and boric acid about 30 grams'per liter, with a current density of 14 to 47 amperesper square foot and at a temperature of 50 to C. The plate obtained in this manner ishard and exceptionally adherent.

It will be understood that in carrying out the invention we may deposit any of the metals noted directly upon the surface of lead or lead-containing metal, or we may deposit a series of coatings, for example copper or brass, with nickel thereon.

' Examination of the surface of the lead or lead containing metal after exposure as the anode to the neutral or alkaline electrolyte shows that the surface is slightly etched. The etching is not suflicient to affect the printing character of the surface, but it affords a bond for the overlying layer or layers of harder metal and prevents peeling and chipping of these layers. The invention is especially advantageous in facilitating the application of nickel to surfaces of lead containing metal.

Printing plates prepared and coated with nickel in the manner described will remain sharp and clear and will show little or no evidence of wear after producing many times the number of im ressions which can be obtained ordinarily rom type metal surfaces.

It is to be understood that the details of plating with the various metals form no part of the present invention and are subject to variation, the rocedures described being merely typical of those well known in the art and adapted for the purpose of the invention, which depends more particularly upon the preparation of the surface to receive these metals and to permit the formation of a satisfactory bond between them and the underlying surface of lead or lead containing metal.

Various changes may be made in the details of the procedure without departing from the invention or sacrificing any of the advantages thereof.

We claim:

1. The method of preparing the surface of lead or a metal containing lead for coating by electrodeposition with another metal which comprises subjecting the surface as the anode to electrolysis in a neutral or alkaline electrolyte.

2. The method of preparing the surface of lead or a metal containing lead for coating by electrodeposition with another metal which comprises subjecting the surface as the cathode to an alkaline cleaning solution and then as the anode to electrolysis in a neutral or alkaline electrolyte.

3. The method of preparing the surface of lead or a metal containing lead for coating by electrodeposition with another metal which comprises subjecting the surface as the anode to electrolysis in a neutral or alkaline elelctrolyte at a voltage of approximately 6 v0 ts.

4. The method of preparing the surface of lead or a metal containing lead for coating by electrodeposition with another metal which comprises subjecting the surface as the anode to electrolysis in a solution of sodium acetate. c 5-. The method of preparing the surface of le'aci'ora metal containin lead for coating by, electrodeposition wit another metal which comprises subjectingthe surface as the anode to electrolysis in a solution containing approximately 50 grams per liter of sodium acetate.

6. The method of improving the wear resistance of surfaces of lead and metal containing lead which comprises subjecting the surface as the anode to electrolysis in a neutral or alkaline electrolyte and thereafter electrodepositing on the prepared surface a harder coating metal.

- 7. The method of improving the wear re taining lead which comprises subjecting the surface as the anode to electrolysis in a neutral or alkaline electrolyte and thereafter electrodepositing on the prepared surface a plurality of layers of harder coating metals.

In testimony whereof we aflix our signatures.

LOUIS WEISBERG. WILLARD F. GREENWALD.