Process for the electrolytic copper plating of zinc diecasting having a reduced tendency to blister formation

Abstract

In the electroplating of zinc diecastings with a copper layer, the electrolyte penetrates into the pores of the zinc diecasting. When the temperature is increased later, this leads to vaporization of the electrolyte liquid in the pores and to blistering or flaking of the copper layer. It is proposed that plating be carried out in two steps. In the first step, only a thin copper layer of less than 1 μm is applied and the plated parts are then treated at a temperature which leads to vaporization of the electrolyte liquid. The thin copper layer is still sufficiently porous for the vapour to be able to escape. Only the solid constituents of the electrolyte remain. The copper layer is then thickened to a final thickness of from about 20 to 30 μm. In this plating step, electrolyte liquid no longer penetrates into the pores of the zinc diecasting. The parts which are coated in this way display no blistering or flaking of the copper layer after storage at a temperature of 150° C.

1 . Process for the copper plating of zinc diecastings having a reduced tendency to blister formation,
 characterized by the steps,   a) deposition of a first copper layer having a thickness of less than 1 μm from a pyrophosphate-containing copper electrolyte,   b) rinsing and drying of the parts at elevated temperature and   c) thickening of the first copper layer in a pyrophosphate-containing copper electrolyte to a thickness in the range from 10 to 20 μm.   
     
     
         2 . Process according to  claim 1 ,
 characterized in that,   in step a), the first copper layer is deposited to a thickness in the range from 0.1 to 0.5 μm.   
     
     
         3 . Process according to  claim 1 ,
 characterized in that,   in step b), the parts are stored at from 100 to 180° C. for a time of from 10 to 60 minutes.