METHOD FOR REMOVING IMPURITIES OF Fe IONS IN SULFURIC ACID BASE ELECTROPLATING SOLUTION TO SUPPRESS BLACKENING DUE TO Fe IONS BY ADDING HYDROGEN PEROXIDE IN ELECTROPLATING LINE

摘要

PURPOSE: To provide a method for removing impurities of Fe ions in sulphuric acid base electroplating solution to produce a blackening suppressed electro-galvanized steel sheet excellent in paintability, corrosion resistance and anti-finger printing property by adding hydrogen peroxide to electroplating solution and adding zinc carbonate to oxidized plating solution, thereby removing Fe ions precipitated in the plating solution. CONSTITUTION: The method comprises a process of analyzing content of Fe ions in the plating solution in real time through a solution component analyzer during an operation of supplying a sulfuric acid base plating solution into a plating bath; a process of performing an oxidation by injecting a predetermined quantity of hydrogen peroxide into the plating solution after stopping supply of the plating solution into the plating bath contained in the oxidation tank if analyzed values exceed a standard value and supplying the plating solution into an oxidation tank(126); a process of forming Fe ions into sludge by adding zinc carbonate to the oxidized plating solution contained in the neutralization tank after transferring an oxidized plating solution into a neutralization tank(128); and a process of filtering the plating solution so that the sludge is separately discharged, and supplying a filtered plating solution only into a circulation tank(110) again.