US2216605A - Electroplating - Google Patents

Description

Patented Oct. 1, 1940 UNITED STATES PATENT OFFICE ELEUIROPLATHVG York No Drawing. Application March 30, 1938,

Serial No. 198,826

2 Claims.

Our invention relates generally to electroplating and more particularly, to a novel electroplating bath.

One of the objects of our invention is to provide a novel electroplating bath of the character described which is adapted to electrodeposit a novel and highly improved alloy plate.

Another object of our invention is to provide a novel electroplating bath of the character described which is adapted to electrodeposit a novel and highly improved alloy plate upon zinc die cast objects and which is at the same time highly resistant to corrosion.

A .further object of our invention is to provide an electroplating bath which will deposit a copper-cobalt-tin alloy plate of the character described with consistently satisfactory results and in a simple and inexpensive manner.

Other objects of our invention will in part be obvious and in part hereinafter pointed out.

In accordance with our invention, a dry composition, that is, an electroplating bath composition, may be prepared by making a mixture of copper salts, cobalt salts, tin salts and an alkaline cyanide. This composition is added to water or any other suitable solvent to form an electroplating bath solution from which may be electrodeposited upon an object. in a manner and by means well known in the art, an alloy plate comprising copper, cobalt and tin.

We have found that when an electroplating bath solution, prepared in accordance with our invention, contains a copper content of from about 0.04 to 15.85 grams per gallon, a cobalt content of from about 0.02 to 9.2 grams per galion, and a tin content of from about 0.02 to 3.6 grams per gallon, a satisfactory copper-cobalttin alloy plate may be electrodeposited therefrom. It is understood, however, that our invention is notto be construed as being limited by these ranges.

In supplying the copper, cobalt and tin contents of the bath, any salt or salts of copper, cobalt and tin may be employed in the dry plating composition which, when combined with other ingredients comprising. the plating composition, will dissolve in the solvent employed. Some of these salts are:

Sodium stannate NazSnOa 3H2O Stannous phosphate Sn3(PO4) 2 Stannous tartrate SnC4H4Oe Copper cyanide Cu2(CN) 2 Copper sulphate CuSO;

Copper tartrate CuC4H4Os Cobaltous sulfate CoSO4-7H2O Cobalt tartrate CoC4H40s Cobalt carbonate CoCOs Cobalt cyanide Co (CN) 2 2H2O Sodium cobaltocyanide Na4Co (CN) 15 Cobalt phosphate Coa(PO4) 2 5 Suftlcient alkaline cyanide should be mixed into the dry bath composition to ensure a free or uncombined alkaline cyanide content in the electroplating bath of from 0.3 ounce to 6 ounces per gallon. We have found that the 10 most satisfactory results are obtained by the presence of 2 to 3 ounces of free alkaline cyanide per gallon.

In connection with the practice of our invention, suitable plating voltages, temperatures and current densities generally known to the art may be employed.

By our invention, saltsof copper, cobalt and tin may be satisfactorily used to electrodeposit a bright plate from an alkaline cyanide electroplating bath for periods of time up to one minute, without the necessity of employing any addition salts for brightening or conductivity. The electroplate thus obtained suflices for an inexpensive and practical plate on articles such as those used in the novelty trade.

When a heavier and more durable plate is desired, we have found that addition agents as brighteners and for conductivity, such as those listed below, may be used. 80

Tri-sodium phosphate NaaPOrHaO Rochelle salt NaKC4H406 4H2O Potassium thiocyanate KCNS Sodium bisulfite N aHSOs Sodium sulfate NazSOr Sodium carbonate NazCOa Sodium arsenite NaAsOz Di-sodium phosphate NacHPO4 Sodium pyrophosphate Na4P2O'1-10H2O Arsenious acid AszO:

Sodium phenylate (phenate) NaCcHsO Goulac (tailings from sulphite liquor concentrate in preparation of wood pulp) Sodium thiosulfate NazSaOs Soda alum Na-A1'(SO4)2-12HzO 5 Glucose CeHmOs Dextrose CsHmOa Dextrine (Col-1100s) x Ammonium molybdate (NH4) 6MO7024'4H2O Sodium oxalate NazCzOr Ammonium hydroxide NHQOH Bone glue Thiourea NI-Iz-CS-NI-Iz Potassium ferrocyanide K;Fe(CN)s The above-listed addition salts are represenu tative members of their groups. For example, Rochelle salt is a. member of the tartrate group and merely given as an example of such. Other tartrates, such as ammonium, copper, magnesium, cobalt or tin tartrate, would cause the plating bath to function equally well.

We have found that satisfactory results are obtained by using .the following addition. salts for brightening or conductivity either singly, doubly, or in multiple combination in the ranges set forth.

Addition mum gf g Eggfig I Gram 6 1m 1 at Twat" Tri-Bodium phosphate 0.01to 28. flodiumarsenitemn 0.01to 1 0. 0.01m 1 0.

333% W-Ira."- 8'81 1 1 3' "Go lTc up a 0101 1:8 1 01 0.01:0 1 0.

0.01 to 1 o.

0.01 to 1 o.

0.01 to 1 o.

0.01 to so 14.

0c. 1101: C r Hon Ammonium hydroxide H. 30 6 pc We have found that the double combinations of addition agents listed below also give good results:

(Grams per gallon) 0.01 Di sodium phos- +1.0 Rochelle salt 1.0 Bone glue 1.0 Bone glue 1.0 Bone glue 1.0 Bone glue +0.01 Sodium bisulfite +0.05 Sodium sulfate +0.05 Soda alum +1.0 Glucose The following are specific examples of dry bath compositions which we have found to give good results, it being understood that they are in no way limltative. The weights given are for use with one gallon of a plating bath.

Example I Grams Sodium stannate 8.60 Sodium cyanide 90.00 Copper cyanide 18.00 Cobalt carbonate 5.80

Emails I! Sodium stannate 8.60 Sodium cyanide 90.00 Copper cyanide--. 18.00 Cobalt carbonate 5.80 Rochelle sal 1.25

123.65 Example III Grams Sodium stannate 8.60 Sodium cy 90.00 Copper cyanide 18.00 Cobalt carbonate; 5.80 Rochelle salt 1.25 Tri-sodium phosphate 7.60

131.25 Example IV Rochelle salt 1.25 Sodium stannate 8.60 Tri-sodium phosphate 7.60 Sodium cy 90.00 Copper cyanide 18.00 Cobaltous sulfate 13.80

We have found that by our invention a ferrocyanide, such as potassium ferrocyanide, may be used to partially replace sodium cyanide in the bath and reduce the effect of carbonate formation from the breakdown of sodium cyanide as is illustrated by the following example:

Grams Cuban cyanide 5.40 Sodium cy L 50.00

Copper cyanide 18.00 Sodium stannate 8.60

82.00 Potassium ferrocyanide 1 to 10 grams.

By our invention, as above described, we have been able to produce an electroplated alloy, characterized by its whiteness which approaches silver, has a high reflectivity, and is at the same time hard and ductile so that metals upon which our alloy has been electrodeposited may be formed without peeling, chipping or cracking. Also, our alloy plate forms a substantially uniform deposit on irregular surfaces due to the high throwing power of the solution. Also, it is highly tarnish-resistant, being unaffected by salt spray, mustard and olives, lemon juice, or the like. The alloy plate is moreover resistant to corrosion by cold caustic or alkaline solutions of any strength and can only be slowly dissolved by any single acid, so that it furnishes a good foundation or primary plate because other plates, such as a chromium plate or a nickel plate, may be readily stripped therefrom without affecting it. This latter characteristic of the alloy plate produced by our invention, namely its excellence as a primary plate, is particularly important in regard to zinc die cast objects on which primary electroplates have heretofore tended to be absorbed or become blistered, or on which difliculty has been experienced in electrodepositing a second plate. We have found that our novel bath will electrodeposit a smooth plate on zinc die cast objects which will not be absorbed and may be used as a base plate for other electrodeposits having any specially desired characteristics.

It will thus be seen that'there is provided a composition, bath and process by means of which the several objects of this invention are achieved, and which are well adapted to meet the conditions of Practical use.

As various possible embodiments might be made of the above invention, and as various changes might be made in the embodiments above set forth, it is to be understood that all matter herein set forth is to be interpreted as illustrative and not in a limiting sense.

Having thus described our invention, we claim as new and desire to secure by Letters Patent:

1. A process of electrodepositing a white copper-cobalt-tin alloy plate comprising passing current through an aqueous alkali cyanide bath solution containing copper salts, cobalt salts and tin salts, the quantities of said salts. being such that the metallic contents of one gallon of said solution will be from about 0.04 to 15.85 grams of copper, from about 0.02 to 9.2 grams of cobalt, and from about 0.02 to 3.6 grams of tin, and having a free alkali cyanide content of from 0.3 to 6 ounces per gallon of solution.

2. An electroplating bath for depositing a white alloy plate of copper, cobalt and tin, said bath comprising an aqueous alkali cyanide solution of copper, cobalt and tin salts and from 0.3 to 6 ounces of free alkali cyanide per gallon of solution, said bath having metallic contents per gallon of solution of from about 0.04 to 15.85 grams of copper, from about 0.02 to 9.2 grams of cobalt and from about 0.02 to 3.6 grams of tin.

1 LIONEL CINAMON.

SAMUEL SKLAREW.