Method of electroplating and pre-treating aluminium workpieces

Abstract

Disclosed is a method of applying a metal layer onto at least one surface of an aluminium or aluminium alloy workpiece, including the steps of pre-treating the surface by cathodic activation in a pre-treatment bath containing sulphuric acid and metal-ions selected from the group consisting of nickel, iron and cobalt, and applying a metal layer by electroplating the pre-treated workpiece. The metal layer is selected from the group consisting of nickel, iron, cobalt, and alloys thereof.

1 . A method of applying a metal layer onto at least one surface of an aluminium or aluminium alloy workpiece, comprising the steps of pre-treating the surface by cathodic activation in a pre-treatment bath containing sulphuric acid and metal-ions selected from the group consisting of nickel, iron and cobalt, and applying a metal layer by electroplating the pre-treated workpiece, and wherein the metal layer is selected from the group consisting of nickel, iron, cobalt, and alloys thereof.  
   
   
       2 . The method according to  claim 1 , wherein the pre-treatment bath comprises 15 to 200 g/l of NiSO 4 .H 2 O and 50 to 350 g/l of H 2 SO 4.    
   
   
       3 . The method according to  claim 1 , wherein the pre-treatment bath comprises 80 to 150 g/l of NiSO 4 .H 2 O and 150 to 250 g/l of H 2 SO 4.    
   
   
       4 . The method according to  claim 1 , wherein the pre-treatment bath further comprises boric acid (H 3 BO 3 ).  
   
   
       5 . The method according to  claim 1 , wherein the pre-treatment bath further comprises 1 to 50 g/l boric acid (H 3 BO 3 ).  
   
   
       6 . The method according to  claim 1 , wherein the pre-treatment bath further comprises 20 to 40 g/l boric acid (H 3 BO 3 ).  
   
   
       7 . The method according to  claim 1 , wherein the plating bath comprises a Watts bath.  
   
   
       8 . The method according to any one of claims  1 , wherein the plating bath comprises a Watts bath comprising a mixture of nickel sulphate (NiSO 4 ), nickel chloride (NiCl 2 ) and boric acid (H 3 BO 3 ).  
   
   
       9 . The method according to  claim 1 , wherein the plating bath comprises a citrate-gluconate bath comprising a mixture of NiSO 4 , and (NH 4 ) 2 SO4 and sodium citrate and sodium gluconate.  
   
   
       10 . The method according to  claim 1 , wherein the plating bath comprises a citrate-gluconate bath comprising a mixture of NiSO 4 , nickel chloride, (NH 4 ) 2 SO 4 , bismuth concentrate, sodium citrate and sodium gluconate.  
   
   
       11 . The method according to  claim 1 , wherein the plating bath comprises a citrate-gluconate bath comprising a mixture of 100 to 180 g/l of NiSO 4 .6H 2 O, 10 to 50 g/l of NiCl 2 .6H 2 O, 1 to 10 ml/l of a bismuth concentrate containing 100 g/l of Bi, 10 to 50 g/l of (NH 4 ) 2 SO 4 , 100 to 180 g/l of sodium citrate.2H 2 O, and 10 to 50 g/l of sodium gluconate.  
   
   
       12 . The method according to  claim 1 , wherein the plating bath comprises a citrate-gluconate bath comprising a mixture of NiSO 4 , nickel chloride, (NH 4 ) 2 SO 4 , sodium citrate and sodium gluconate.  
   
   
       13 . The method according to  claim 1 , wherein the plating bath comprises a citrate-gluconate bath comprising a mixture of 100 to 180 g/l of NiSO 4 .6H 2 O, 10 to 50 g/l of NiCl 2 .6H 2 O, 10 to 50 g/l of (NH 4 ) 2 SO 4 , 100 to 180 g/l of sodium citrate.2H 2 O, and 10 to 50 g/l of sodium gluconate.  
   
   
       14 . The method according to  claim 1 , wherein the pre-treatment bath is devoid of any fluoride containing components.  
   
   
       15 . The method according to  claim 1 , wherein the temperature of the pre-treatment bath is maintained at an elevated temperature in a range of above room temperature to 95° C.  
   
   
       16 . The method according to  claim 1 , wherein the temperature of the pre-treatment bath is maintained at a temperature in a range of 55° C. to 80° C.  
   
   
       17 . The method according to  claim 1 , wherein the temperature of the pre-treatment bath is maintained at a temperature in a range of between about 60° C. and 70° C.  
   
   
       18 . The method according to  claim 1 , wherein the cathodic activation applies an activation current in a range of −200 to −2000 A/m 2 ,  
   
   
       19 . The method according to  claim 1 , wherein the cathodic activation applies an activation current in a range of −500 to −1400 A/m 2 .  
   
   
       20 . The method according to  claim 1 , wherein the time spent by the product in the pre-treatment bath is in the range of 1 to 50 sec.  
   
   
       21 . The method according to  claim 1 , wherein the time spent by the product in the pre-treatment bath is in the range of 5 to 15 sec.  
   
   
       22 . The method according to  claim 1 , wherein the applied metal layer has an average thickness of less than 2 μm.  
   
   
       23 . The method according to  claim 1 , wherein the applied metal layer has an average thickness of less than 1.0 μm.  
   
   
       24 . The method according to  claim 1 , wherein the applied metal layer has an average thickness of 0.2 to 1.0 μm.  
   
   
       25 . The method according to  claim 1 , further comprising applying a second metal layer on top of the layer of Ni, Fe, Co, or alloys thereof.  
   
   
       26 . The method according to  claim 1 , wherein the layer of Ni, Fe, Co, or alloys thereof is a nickel-containing layer, further comprising applying a tin-containing layer on top of the nickel-containing layer.  
   
   
       27 . The method according to  claim 1 , wherein the method is carried out as a continuous plating operation.  
   
   
       28 . The method according to  claim 1 , wherein the aluminium workpiece is a brazing sheet product, the brazing sheet product including a core layer and a clad layer formed of a brazing alloy including aluminium and 2-18 wt. % silicon, and whereby the metal layer is applied on the clad layer.  
   
   
       29 . The method according to  claim 28 , wherein the clad layer further comprises as alloying element a wetting agent in a range of up to 1 wt. %.  
   
   
       30 . The method according to  claim 29 , wherein the wetting agent is selected from the group consisting of lead, bismuth, lithium, antimony, tin, silver, thallium and any mixture thereof.  
   
   
       31 . The method according to  claim 1 , wherein the aluminium workpiece is an aluminium conductor, and preferably made of an alloy selected from the group consisting of AA1370, AA1110 and AA6101.  
   
   
       32 . An aluminium alloy product, electrolytically plated with a metal layer selected from the group consisting of nickel, iron, cobalt and alloys thereof by using the method of  claim 1.