Patented Dec. 9, 1952 2,621,152

UNITED STATES PATENT OFFICE I

‘ZINC CYANIDE PLATING BATH Raymond A. Hoffman, Euciid,;0hio,'assignorsto Allied‘ Research Products, 1 Incorporated” Balti more, Md., a corporation-of-Maryland No-Drawing. Application-March "30, 1950 Serial No. 152,999 ~ 7 Claims. (Cl. 204-—5.5) ,1 ,2 . ~ This invention relates to the electrodeposition Heat is applied until the mixture boils and is of zinc, and is particularly directed to processes continued for a period of 11/2 to 2 hours after wherein a bright mirror-like zinc deposit is which time the reaction is considered complete. plated from cyanide zinc baths which contain ‘ The clear somewhat syrupy liquid obtained at the substantial amounts of a soluble resinous mate end of this period is ready for use as a brightener rial prepared as hereinafter described. for zinc deposits from cyanide zinc plating baths. An object of the invention is to provide a For convenience I hereinafter term this product plating solution for the deposition of a zinc coat the “B” solution. ing which is materially brighter in surface ap When the “B” solution is made up it is added pearance than zinc coatings heretofore obtain to the “A” solution in the proportion of about able by commercial zinc plating processes, and .25 gram of “3" per liter of “A” to 2.0 grams of which is at least the equal of such commercial “B” per liter of “A.” process in corrosion resistance and wear resist As is customary, the article to be plated con stitutes the cathode, and a zinc anode is im ance. 15 mersed in the solution, the anode being eventually As a basic solution I use the well known zinc consumed. The customary factors in plating cyanide plating bath which, as is known to those processes, namely time, temperature, solution skilled in the art, may vary within recognized concentration, and current density have their composition limits in accordance with certain usual eilects in the plating solution herein dis desired characteristics and process limitations. I closed. One such composition, for example, could be: The plated coating obtained by means of my G. per liter novel bath composition as hereinabove disclosed, Zinc cyanide (Zn(CN)2) ______60 has a surface appearance having a smooth Sodium cyanide (NaCn) ______42 satiny-silver luster. It is wear resistant and Sodium hydroxide (NaOI-I) ______78 25 corrosion resistant, and its brightness is sub For convenience this will be hereinafter referred stantially permanent. What I claim is: to as the “A” solution, and my present invention 1. As an added component for a zinc cyanide resides in the discovery of a novel product ob plating bath, an aqueous solution containing the tained by reacting four separate ingredients in reaction product obtained by heating together aqueous solution. The product obtained as here in aqueous solution from 10 to 30 grams of am inafter set forth, when combined with the “A” monium thiocyanate, from 10 to 30 grams of di solution (or any conventional or useful zinc cya cyandiamide, from 4 to 15 grams of sodium hy nide plating bath) produces the exceptionally droxide, and from 40 to 100 grams of formalde bright plated surface described above. The iden hyde. tity and amount of each material entering into 2. A zinc cyanide plating bath containing from the manufacture of the brightening agent is as 0.25 gram to 2.0 grams of an addition compo follows: nent per liter of bath, said addition component Grams containing the reaction product obtained by Ammonium thiocyanate ______10-30 heating together in aqueous solution from 10 to Dicyandiamide ______10-30 30 grams of ammonium thiocyanate, from 10 to Sodium hydroxide ______4-15 30 grams of dicyandiamide, from 4 to 15 grams Formaldehyde ______40-100 of sodium hydroxide, and from 40 to 100 grams Water ______-_ 40-100 per liter of formaldehyde. More speci?cally, the following composition of 3. A plating bath as de?ned in claim 2, wherein ingredients has been found to produce the de the ingredients of the addition component are sired results after a re?uxing period of 11/; to 2 heated together in the following proportions,’ hours. ammonium thiocyanate 24 grams, dicyandiamide Grams 21 grams, sodium hydroxide 10 grams, formal Ammonium thiocyanate ______24 50 dehyde 75 grams. Dicyandiamide ______21 4. A plating composition as de?ned in claim 3, Sodium hydroxide ______10 wherein the addition component is added to the Formaldehyde ______'75 zinc cyanide bath in the proportion 0.25 gram Water ______60 to 2.0 grams of the component to one liter of the The materials thus shown are placed in a closed bath. vessel to which a re?ux condenser is attached. 5. A method for electrodepositing zinc from 2,621,152 3 4 cyanide zinc plating baths in the form of bright '7. An addition component for a zinc cyanide mirror-like deposits, said method comprising plating bath comprising the reaction product ob electrodepositing the Zinc from a cyanide zinc tained by heating together in aqueous solution plating bath containing, per liter of bath, from ammonium thiocyanate, dicyandiamide, sodium 0.25 to 2.0 grams of the reaction product ob hydroxide and formaldehyde in the following tained by reacting together in aqueous solution proportions, from 10 to 30 grams of ammonium from 10 to 30 grams of ammonium thiocyanate, thiocyanate, from 10 to 30 grams of dicyandi from 10 to 30 grams of dicyandiamide, from 4 to amide, from 4 to 15 grams of sodium hydroxide, 15 grams of sodium hydroxide and from 40 to from 40 to 100 grams of formaldehyde, and 40 100 grams of formaldehyde. 10 to 100 grams of water. 6. An addition component for a zinc cyanide RAYMOND A. HOFFMAN. plating bath comprising the reaction product obtained by heating together in aqueous solution REFERENCES CITED ammonium thiocyanate, dicyandiamide, sodium The following references are of record in the hydroxide and formaldehyde in the following 15 ?le of this patent: proportions, from 10 to 30 grams of ammonium thiocyanate, from 10 to 30 grams of dicyandi UNITED STATES PATENTS amide, from 4 to 15 grams of sodium hydroxide Number Name Date and from 40 to 100 grams of formaldehyde. 2,101,580 Henricks ______Dec. '7, 1937