Low hydrogen embrittlement (LHE) zinc-nickel plating for high strength steels (HSS)

Abstract

The invention provides a method for producing a corrosion-resistant article, where the article is conductive and subject to hydrogen uptake during electroplating of a coating. The method comprises electroplating a zinc-nickel coating on the article in an aqueous, basic plating solution containing zinc and nickel ions. The method uses an electrolyte in the form of a soluble hydroxide salt with the weight ratio of zinc ions to nickel ions in the solution being sufficient to provide the coating comprising from about 85% to about 95% by weight zinc, and about 5% to about 15% by weight nickel. The plating solution is substantially free of brightening agents which retard hydrogen bake-out.

1 . A method for producing a corrosion-resistant article, said article being conductive and subject to hydrogen uptake during electroplating of a coating, said method comprising: 
 electroplating a zinc-nickel coating on said article in an aqueous, basic plating solution containing zinc ions and nickel ions, an electrolyte in the form of a soluble hydroxide salt, the weight ratio of zinc ions to nickel ions in said solution being sufficient to provide said coating comprising from about 85% to about 95% by weight zinc, and about 5% to about 15% by weight nickel, provided that said plating solution is substantially free of brightening agents.    
   
   
       2 . The method of  claim 1 , wherein said plating solution is substantially free of said brightening agents which retard hydrogen bake-out.  
   
   
       3 . The method of  claim 1 , wherein said article when coated is dull in appearance relative to an article coated in the presence of the brightening agents.  
   
   
       4 . The method of  claim 1 , wherein the article comprises high-strength steel and the article when coated has low hydrogen embrittlement.  
   
   
       5 . The method of  claim 1 , wherein the article when coated has the low hydrogen embrittlement being low relative to an article coated in the presence of brighteners.  
   
   
       6 . The method of  claim 1 , wherein the article is plated at a current density of at least about 25 amperes per square foot.  
   
   
       7 . The method of  claim 1 , wherein the article is coated at a current density of less than 75 amperes per square foot.  
   
   
       8 . The method of  claim 1 , wherein the article is coated at a current density of about 30 amperes per square foot up to about 70 amperes per square foot.  
   
   
       9 . The method of  claim 1 , wherein the current density is about 30 to about 68 amperes per square foot.  
   
   
       10 . The method of  claim 1 , wherein the zinc ions of said solution are provided by a precursor zinc compound.  
   
   
       11 . The method of  claim 1 , wherein the nickel ions of said solution are provided by a precursor nickel compound.  
   
   
       12 . The method of  claim 1 , wherein the hydroxide salt contains a group one alkali metal.  
   
   
       13 . The method of  claim 1 , wherein the hydroxide salt is sodium hydroxide.  
   
   
       14 . The method of  claim 1 , wherein the plating solution comprises a nickel complexing agent.  
   
   
       15 . The method of  claim 14 , wherein the nickel complexing agent is diethylene triamine.  
   
   
       16 . The method of  claim 1 , wherein the plating solution is at a pH in a range of at least about 12 and less than 14.  
   
   
       17 . The method of  claim 1 , wherein the zinc ion is present in an amount ranging from about 1.17 to about 1.45 ounces per gallon; the nickel ion is present in an amount ranging from about 0.12 to about 0.15 ounces per gallon and the sodium hydroxide is present in an amount ranging from about 17.4 to about 21.2 ounces per gallon.  
   
   
       18 . The method of  claim 1 , wherein the weight ratio of zinc to nickel is in a range of about 10:1 to about 11:1.  
   
   
       19 . An aqueous composition for the electrodeposition of zinc-nickel alloys which comprises: 
 at least one ounce per gallon zinc, at least 0.1 ounce per gallon nickel, at least 15 ounces per gallon sodium hydroxide, a weight ratio of zinc/nickel of at least 10:1, a pH of at least 12 and less than 14, and being substantially free of brightening agents.    
   
   
       20 . An aqueous composition for the electrodeposition of zinc-nickel alloys which consists essentially of: 
 at least one ounce per gallon zinc, at least 0.1 ounce per gallon nickel, at least 15 ounces per gallon sodium hydroxide, a weight ratio of zinc/nickel of at least 10:1, a pH of at least 12 and less than 14, and being substantially free of organics except for nickel-complexing agents.