Cyanide-free pre-treating solution for electroplating copper coating layer on magnesium alloy surface and a pre-treating method thereof

Abstract

A pre-treating solution for electroplating magnesium alloy surface contains copper ions, a complexing agent and an additive, wherein the complexing agent is selected from potassium sodium tartrate, potassium tartrate, sodium tartrate, tartaric acid, and dissolvable salts derivative from tartaric acid and the additive is selected from sodium phosphate, sodium hypophosphite, phosphoric acid and dissolvable salts derivative from phosphoric acid or hypophosphite acid. The magnesium alloy is dipped in the pre-treating solution and electroplated with a copper coating layer. Then, the magnesium alloy is further dipped in a copper sulfate solution for thickening the copper coating layer and lastly coated with an anti-corrosion metal layer. Thereby, magnesium alloy has excellent anti-corrosion and anti-wearing efficiency and varnish appearance. Moreover, the pre-treating solution contains no cyanide and thus is low toxic and safe to operator during electroplating and to environment after discharging.

1 . A pre-treating method for magnesium alloy surface comprising steps of:
 (a) degreasing: a prepared workpiece made of magnesium alloy is degreased with a degreasing agent to remove oil and dirt from surface of the prepared workpiece;   (b) washing: the prepared workpiece is washed to remove the degreasing agent and to keep the surface of the prepared workpiece clean;   (c) copper electroplating: the prepared workpiece is dipped into a pre-treating solution with auxiliary electrodes and electroplated to obtain a copper coating layer by applying a fixed current from an additional power supplier; and   (d) drying: the pre-treating solution residual on the prepared workpiece is removed from the surface of the workpiece to make the surface dry rapidly.   
     
     
         2 . The pre-treating method as claimed in  claim 1  further comprising a washing step after (c) step of copper electroplating. 
     
     
         3 . The pre-treating method as claimed in  claim 1 , wherein the fixed current provided by the additional power supplier has a range from 0.01 to 0.15 ampere per square decimeter. 
     
     
         4 . The pre-treating method as claimed in  claim 1 , wherein the auxiliary electrodes are made of material selected from the group consisting of titanium core coated with platinum, titanium, platinum, graphite and stainless steel. 
     
     
         5 . The pre-treating method as claimed in  claim 1 , wherein surface temperature of the prepared workpiece in (c) step of copper electroplating is 10 to 90° C. 
     
     
         6 . The pre-treating method as claimed in  claim 1 , wherein the workpiece is further treated with another copper electroplating process and a nickel coating process after the step of drying. 
     
     
         7 . The pre-treating method as claimed in  claim 1 , wherein the pre-treatment solution comprises an aqua solution added with copper ions, a complexing agent and an additive. 
     
     
         8 . The pre-treating method as claimed in  claim 7 , wherein the pre-treatment solution comprises
 the complexing agent selected from the group consisting of potassium sodium tartrate, potassium tartrate, sodium tartrate, tartaric acid, and dissolvable salts derivative from tartaric acid; and   the additive selected from the group consisting of sodium phosphate, sodium hypophosphite, phosphoric acid and dissolvable salts derivative from phosphoric acid or hypophosphite acid.   
     
     
         9 . The pre-treating method as claimed in  claim 7 , wherein the additive is 5 to 50 g/L in concentration. 
     
     
         10 . The pre-treating method as claimed in  claim 7 , wherein the complexing agent is 25 to 150 g/L in concentration. 
     
     
         11 . The pre-treating method as claimed in  claim 7 , wherein the copper ions are obtained from the group consisting of copper chloride, copper sulfate, copper pyrophosphate and hydrates of foregoing motioned salts. 
     
     
         12 . The pre-treating method as claimed in  claim 7 , wherein the copper ions are 5 to 50 g/L in concentration. 
     
     
         13 . A pre-treatment solution for coating a copper layer on a magnesium alloy, the pre-treatment solution comprising an aqua solution added with copper ions, a complexing agent and an additive, wherein
 the complexing agent is selected from the group consisting of potassium sodium tartrate, potassium tartrate, sodium tartrate, tartaric acid, and dissolvable salts derivative from tartaric acid; and   the additive is selected from the group consisting of sodium phosphate, sodium hypophosphite, phosphoric acid and dissolvable salts derivative from phosphoric acid or hypophosphite acid.   
     
     
         14 . The pre-treating solution as claimed in  claim 13 , wherein the additive is 5 to 50 g/L in concentration. 
     
     
         15 . The pre-treating solution as claimed in  claim 13 , wherein the complexing agent is 25 to 150 g/L in concentration. 
     
     
         16 . The pre-treating solution as claimed in  claim 13 , wherein the copper ions are obtained from the group consisting of copper chloride, copper sulfate, copper pyrophosphate and hydrates of foregoing motioned salts. 
     
     
         17 . The pre-treating solution as claimed in  claim 13 , wherein the copper ions are 5 to 50 g/L in concentration.