PRACTICAL AND THEORETICAL ASPECTS OF REGENERATION OF CHROMIC-ACID PLATING SOLUTIONS VIA ELECTROLYTIC PURIFICATION (POROUS POT METHOD)

Most common metallic impurities, such as Ni, Zn, Fe, Cu and Cr(III) io ns found in decorative (bright) or functional (hard) hexavalent chromi um plating solutions can be effectively removed and concentrated as a sludge by electrolytic coagulation, using a porous ceramic separator, Experiments were carried out in a laboratory-scale porous pot at two c urrent levels, The Sargent type, hard chromium plating solution contai ning simulated metallic impurities was used, In the same process, Cr(I II) is effectively oxidized to Cr(VI) at the outside insoluble lead an ode, The results show that optimum conditions for efficient operation depend on current density, initial pH and nature of the cathode. From cyclic voltammograms, pH measurements, metal removal rates and theoret ical principles, complex electrochemical and chemical processes involv ed were analyzed, They are presented as much as possible in simplified form, A set of practical guidelines is detailed.