US2227454A - Method of gold plating steel and ferrous alloys - Google Patents

Description

Passed J....1,- 941 12 227,454

yUNlTED STATES PATENT "'o F1 Joseph B. Kusimer, New York, N. Y., assignor to Benjamin Robinson, New York, N. Y.

No Drawing. Application November 11, 1937, Serial No. 174,054

3 Claims. (M. N L-12') This invention relates to an improved method in the gold plating bath and the platingoperator plating gold on steel and ferrous alloys, the tion commenced. The preferable gold plating object being to produce a methodwhereby gold bath consists of the following ingredients in apmay be plated directly on steel, iron, and other proximately the following proportions:

5 desired ferrous material in a way to be securely I Grams united with the article being plated. Potassium cy 100 5 In carrying out the invention it has been found Potassium carbonate 80 that certain solutions hereinafter fully set forth Potassium gold cyanideaui A- 20 must be used to properly cleanse a metal article Ammonium benzoate a 2.5 m oi oxide. It also has been found that the plating $odium form l- 2.5

solution must contain a special reagent to inhibit the free acid remaining on the metal from at- Water make l tacking the surface of the metal during the plat- It will be noted that the ammonium benzoate ihg operation. and sodium formate are reagents and act to pre to When plating an article of steel or ferrous alvent too rapid plating. These inhibitors are deloy, the article is first thoroughly cleaned of all sirable to cause a fine solid plating to be secured. ordde and is also etched to a certain extent, It will therefore be seen that theformate and namely, until a line etched surface is secured, so henzoate in the DI D Set with lower the as to present an appreciably greater area to which oxidizing effect of the free cyanide on the article no the gold may cling. More specifically, in carrybeing plated by depressing the CN ionization. The

ing out the method the article is first cleansed in gold has therefore the opportunity of being dea suitable alkaline cleanser. -The article is then posited on the surface of the article before 'a dipped in a special bath to remove all oxide film tarnish film can be formed on it. from the cleansed article. The desired bath for As eq iv lents for h en s nd the other W this purpose is set forth in the following formula: gold plating salts the following could be used;

By volume I KAuCna NaAu(CN)2 I Parts or NH4Au(CN)2 llythoduosilicle acid (concentrated), KrCOa NazCOs m 50 to 100 g or NHiCOs so l-lydrofluoric acid HF 5 KCN NaCN Water (distilled), H20 25 to 50 sum 1 t or NHMCN) A substitute for the acid hydrofluosilicic could Pmssmm mate 1H? fluoboric acid or the acids of the combination I or Ammonium mrmate all of fluorine and the silicon earth group. Acids of g fi bemoate} or Potassium benzoate 35 this type, while sufilciently strong to destroy the oxide film on steel do not appreciably aflect the It will, of course, be understood that the artiunder surface during a short exposure to them, cle may be submerged in the plating bath as and are therefore also suitable for the purpose of long as desired with the full current flowing. w the present invention. For an extremely light plating coat five or six 40 The article to be plated is dipped in the above seconds would probably be satisfactory but ususolutlon to secure the removal of the oxide fllm. ally the article 'is left in the bath for a longer This dipping operation may be from 30 seconds time, as, for instance, one-hall hour or longer to 2 minutes according to the amount of etching with a current from 1 to 6 volts As the sur- 4,5 desired as the solution will not only remove the face is clean and is also formed with fine etch- 4 oxide film but will etch the surface of the article ing, the gold deposited on the article will interto be plated. This dipping may be done by ordilock with the etched surface and form substannary dipping or current maybe used and caused tially an integral part thereof so that the plated to pass through the article during the dipping article may be brushed or buffed, or polished in to operation. This will produce a stronger etching any desired way and without becoming loose or eflect. in any way injured.

After the article has been dipped as Just'de- I claim: scribed it is immediately immersed in clean water, 1. The method of electroplating gold on ferw ich m y be o Arter quic dippin the rous metals consisting in cleaning the article to 65 article in clean water it is immediately immersed be plated in an alkaline bath, subjecting the herent state.

2. The method of plating gold on steel and ferrous alloy articles consisting in subjecting the article to a mild ionized acid bath until all of the oxide on the article has been removed and the surface of the article has been attached sufiiciently to enlarge its surface by a very fine etched surface, washing the article in water and immediately subjecting the article to an electroplating action in a plating bath containing potassium cyanide, potassium carbonate, potassium gold cyanide and a reagent consisting of ammonium benzoate and sodium for- ,mate acting to cause the lowering of the attacking effect of the free cyanide on the article by depressing the ionization to permit the gold to be deposited on the surface of the article before a tarnish film can form.

3. The method of gold plating an article of ferrous material on which an oxide film normally forms which includes subjecting the article to hydrofluosilicic acid until the oxide film has been removed and an etching operation has taken place to increase the surface, and electrolytically depositing a gold plate on the etched article from a cyanide plating bath containing ammonium benzoate and sodium formate.

JOSEPH B. KUSHNER.