Pre-Treatment Method for Plating and Instrument for Waterworks of Lead-Contained Copper Alloy

Abstract

A pre-treatment method for plating wherein lead or the like dissolved in an etching liquid is not electro-deposited (re-adhesion) on a lead-contained copper alloy to be plated even without adding a chelating agent forming an insoluble inert combined substance. The lead-contained copper alloy to be plated is dipped in an alkaline etching liquid without adding a chelating agent which would form an insoluble inert combined substance. In this state, electrolysis where the lead-contained copper alloy functions as one of a positive electrode and a negative electrode, and electrolysis where the lead-contained copper alloy functions as the other of the positive electrode and the negative electrode are performed alternately (PR electrolysis).

1 . A plating pre-treatment method for plating of preliminarily removing lead existing on a surface layer of a lead-contained copper alloy prior to carrying out plating on the surface, comprising the steps of:
 alternately performing electrolysis where said lead-contained copper alloy functions as one of a positive electrode and a negative electrode, and electrolysis where said lead-contained copper alloy functions as the other of the positive electrode and the negative electrode, the steps being performed in a state where said lead-contained copper alloy is dipped in an alkaline etching liquid.   
   
   
       2 . The pre-treatment method for plating according to  claim 1 , wherein said lead-contained copper alloy functions as the positive electrode in a last-performed one of said electrolysis steps. 
   
   
       3 . The pre-treatment method for plating according to  claim 1 , wherein the electrolysis steps are performed with conditions of an electric current density of 1 A/dm 2  r more and 25 A/dm 2  or less and a current reversing period of 2 seconds or more and 30 seconds or less. 
   
   
       4 . The pre-treatment method for plating according to  claim 1 , said alkaline etching liquid contains an oxidizing agent. 
   
   
       5 . The pretreatment method for plating according to  claim 1 , wherein nickel plating is carried out and thereafter chromium plating is carried out as said plating on the surface of the lead-contained copper alloy after said electrolysis steps. 
   
   
       6 . A plating pre-treatment method for a surface of an instrument for waterworks of a lead-contained copper alloy comprising the steps of: alternately performing electrolysis where said lead-contained copper alloy functions as one of a positive electrode and a negative electrode, and electrolysis where said lead-contained copper alloy functions as the other of the positive electrode and the negative electrode, the steps being performed in a state where said lead-contained copper alloy is dipped in an alkaline etching liquid. 
   
   
       7 . The plating pre-treatment method according to  claim 6 , wherein in the electrolysis performed alternately with the positive electrode and the negative electrode, said lead-contained copper alloy functions as the positive electrode in a last-performed one of the electrolysis steps. 
   
   
       8 . The plating pre-treatment method according to  claim 6 , wherein the electrolysis steps are performed with conditions of an electric current density of 1 A/dm 2  or more and 25 A/dm 2  or less and a current reversing period of 2 seconds or more and 30 seconds or less 
   
   
       9 . The plating pre-treatment method according to  claim 6 , wherein said alkaline etching liquid contains an oxidizing agent. 
   
   
       10 . The pre-treatment method for plating according to  claim 2 , wherein the electrolysis steps are performed with conditions of an electric current density of 1 A/dm 2  or more and 25 A/dm 2  or less and a current reversing period of 2 seconds or more and 30 seconds or less. 
   
   
       11 . The pre-treatment method for plating according to  claim 2 , said alkaline etching liquid contains an oxidizing agent. 
   
   
       12 . The pre-treatment method for plating according to  claim 2 , wherein nickel plating is carried out and thereafter chromium plating is carried out as said plating on the surface of the lead-contained copper alloy after said electrolysis steps. 
   
   
       13 . The plating pre-treatment method according to  claim 7 , wherein the electrolysis steps are performed with conditions of an electric current density of 1 A/dm 2  or more and 25 A/dm 2  or less and a current reversing period of 2 seconds or more and 30 seconds or less 
   
   
       14 . The plating pre-treatment method according to  claim 7 , wherein said alkaline etching liquid contains an oxidizing agent.