Copper-tin electrolyte and process for the deposition of bronze layers

Abstract

Consumer goods and industrial articles are electroplated with bronze layers for decorative purposes and for protection against corrosion. The electrolytes used hitherto for producing decorative bronze layers are cyanide-containing or, as in the case of baths based on organosulfonic acids, highly corrosive, or, as in the case of cyanide-free baths based on diphosphoric acid, give unsatisfactory brightness and shine. The present invention provides a nontoxic electrolyte for the electrochemical deposition of uniformly bright and shiny bronze layers and a corresponding process for the application of such decorative bronze layers to consumer goods and industrial articles, by means of which relatively thick bronze layers can also be deposited electrochemically in a satisfactory way.

1 . A nontoxic electrolyte for the deposition of decorative bronze alloy layers on consumer goods and industrial articles, which contains the metals to be deposited in the form of water-soluble salts,
 wherein   the electrolyte comprises one or more phosphonic acid derivatives as complexing agents and a brightener system composed of a disulfide compound and a carbonate or hydrogencarbonate salt.   
     
     
         2 . The electrolyte as claimed in  claim 1 ,
 wherein,   it contains the metal ions of copper and tin or copper, tin and zinc to be deposited.   
     
     
         3 . The electrolyte as claimed in  claim 2 ,
 wherein   the water-soluble salts of the metals to be deposited are selected from the group consisting of pyrophosphates, carbonates, hydroxide-carbonates, hydrogencarbonates, sulfites, sulfates, phosphates, nitrites, nitrates, halides, hydroxides, oxide-hydroxides, oxides and combinations thereof.   
     
     
         4 . The electrolyte as claimed in  claim 1 ,
 wherein   the metals to be deposited are present in dissolved form, with the ion concentration of copper being in the range from 0.2 to 10 gram per liter of electrolyte, the ion concentration of tin being in the range from 1.0 to 30 gram per liter of electrolyte and the ion concentration of zinc, if present, being in the range from 1.0 to 20 gram per liter of electrolyte.   
     
     
         5 . The electrolyte as claimed in  claim 1 ,
 wherein   it comprises, as carbonate or hydrogencarbonate salt, a salt of this type selected from the group consisting of alkali metal and alkaline earth metal salts.   
     
     
         6 . The electrolyte as claimed in  claim 5 ,
 wherein   the carbonate or hydrogencarbonate ions are present in an amount of 0.5-100 g/l of electrolyte.   
     
     
         7 . The electrolyte as claimed in  claim 1 ,
 wherein   it comprises, as disulfide compound, a compound of this type selected from the group consisting of substituted and unsubstituted bisalkyl or bis(hetero)aryl or alkyl (hetero)aryl disulfides.   
     
     
         8 . The electrolyte as claimed in  claim 7 ,
 wherein   the disulfide compound is present in the electrolyte in an amount of 0.01 mg/l-10.0 g/l.   
     
     
         9 . The electrolyte as claimed in  claim 1 ,
 wherein   it contains, as phosphonic acid derivatives, one or more compounds selected from the group consisting of 1-aminomethylphosphonic acid AMP, aminotris(methylenephosphonic acid) ATMP, 1-aminoethylphosphonic acid AEP, 1-aminopropylphosphonic acid APP, (1-acetylamino-2,2,2-trichloroethyl)phosphonic acid, (1-amino-1-phosphonooctyl)phosphonic acid, (1-benzoylamino-2,2,2-trichloroethyl)phosphonic acid, (1-benzoylamino-2,2-dichlorovinyl)phosphonic acid, (4-chlorophenylhydroxymethyl)phosphonic acid, diethylenetriamine-penta(methylenephosphonic acid) DTPMP, ethylenediaminetetra(methylenephosphonic acid) EDTMP, 1-hydroxyethane(1,1-di-phosphonic acid) HEDP, hydroxyethylaminodi(methylenephosphonic acid) HEMPA, hexamethylenediaminetetra(methylphosphonic acid) HDTMP, ((hydroxymethylphosphonomethylamino)methyl)phosphonic acid, nitrilotris(methylenephosphonic acid) NTMP, 2,2,2-trichloro-1-(furan-2-carbonyl)amino-ethylphosphonic acid, salts derived therefrom and condensates derived therefrom, or combinations thereof.   
     
     
         10 . The electrolyte as claimed in  claim 1 ,
 wherein   the pH of the electrolyte is in the range from 6 to 14.   
     
     
         11 . The electrolyte as claimed in  claim 1 ,
 wherein   pyrophosphate ions are present in the electrolyte.   
     
     
         12 . The electrolyte as claimed in  claim 1 ,
 wherein   one or more stabilizing compounds selected from the group consisting of monocarboxylic and dicarboxylic acids, alkanesulfonic acids, betaines and aromatic nitro compounds are present.   
     
     
         13 . A process for the electrochemical application of decorative bronze alloy layers to consumer goods and industrial articles, in which the substrates to be coated are dipped into an electrolyte containing the metals to be deposited in the form of water-soluble salts,
 wherein   a nontoxic electrolyte as claimed in  claim 1  is used.   
     
     
         14 . The process as claimed in  claim 13 ,
 wherein   the electrolyte is maintained in the range from 20 to 70° C. during deposition of the metals.   
     
     
         15 . The process as claimed in  claim 13 ,
 wherein   a current density in the range from 0.01 to 100 ampere per square decimeter is set.