TREATMENT OF LEAD-CONTAINING COPPER ALLOY FOR SUPPRESSING LEACHING OF LEAD AND IMPLEMENT FOR WATER SERVICE MADE OF LEAD-CONTAINING COPPER ALLOY

摘要

PROBLEM TO BE SOLVED: To effectively prevent the leaching of lead from an implement during use by immersing a lead-containing copper alloy in a phosphoric acid added chromate solution after immersion in an alkali etching solution to form a chromate coating.;SOLUTION: A lead-containing copper alloy is immersed in a phosphoric acid added chromate solution. By the synergistic effect of chromic acid and phosphoric acid contained in the chromate solution, a chemical reaction in which lead in the surface of the copper alloy is dissolved and a chemical reaction in which a chromate coating is formed occur. Even a little lead remaining in the surface of the copper alloy is dissolved and removed and the lead-free surface is protected with the chromate coating. The leaching of lead from the interior of the copper alloy by corrosion due to long- term water circulation can be suppressed over a long period of time. When the copper alloy is immersed in an alkali etching solution containing an added oxidizing agent before the immersion in the chromate solution, lead in the surface of the copper alloy is converted into a water-soluble alkali metallic plumbite and the dissolution of lead is accelerated.;COPYRIGHT: (C)2000,JPO