ELECTROLYSIS PROCEDURES FOR REGENDING AN EISEN-III CHLORIDE OR EISEN-III SULPHICLE SOLUTION, MORE SPECIFIC TO THE PROCESSING OF STEEL

摘要

An electrolysis process for regenerating a ferric chloride or sulphate solution (etchant), in particular for spray etching steel, is disclosed. The etchant to be regenerated continuously flows through the anode chamber (17) of an electrolytic cell (10) whose cathode chamber (14) is filled with a diluted conductive acid. Anode and cathode chambers (12 and 14) are separated by a cation exchange membrane (16) through which Fe(II) ions, excess Fe(III) and dissolved non-ferrous metals, in particular nickel and chromium ions, reach the cathode chamber (14), while Fe(II) ions are oxidised into FE(III) ions at the anode. The metals accumulated in the catholyte preferably precipitate as a powder in the cathode chamber (14) or are electrolytically precipitated in a subsequent electrolytic cell whose cathode and anode chambers are separated by an anion exchange membrane. This process allows the etchant to be continuously regenerated in a closed circuit, ensures the depletion of non-ferrous metals and excess iron, as well as the electrolytic precipitation of the depleted metal ions.