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REGENERATION OF CHROMATED ALUMINUM DEOXIDIZERS. IMPROVED DIAPHRAGM FABRICATION AND PERFORMANCE
Citation:
Hicks, H. AND D. Sekits. REGENERATION OF CHROMATED ALUMINUM DEOXIDIZERS. IMPROVED DIAPHRAGM FABRICATION AND PERFORMANCE. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/2-77/194.
Description:
In the metal finishing industry highly concentrated hexavalent chromium solutions are used extensively to deoxidize aluminum surfaces prior to anodizing, conversion coatings, prepaint preparation, welding and adhesive bonding. A regeneration process was conceived and tested to reduce the frequency of discarding the spent chromated deoxidizers. The engineering techniques developed in this project involve reoxidation of trivalent chromium to the hexavelent state by electrolysis thru a diaphragm plus removal of undesirable dissolved metals by crystallization and separation. Results of the accomplished work establish that regeneration of chromated aluminum deoxidizers is feasible, practical and economical. In the second phase of this project diaphragm fabrication techniques were refined to produce an improved diaphragm in terms of cost and performance. In addition, electrolytic regeneration equipment installed in a large production tank for six months exceeded technical and economic objectives.