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Multi-Parameter Controller Solves Chromium Problem

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An FAA Certified Part 145 Repair Station MRO facility was unable to discharge to their POTW because the hexavalent chromium Cr(VI) concentration in their wastewater stream was over the regulated discharge limit.

Cr(VI) is an unavoidable waste product when refurbishing and manufacturing heat exchangers for aircraft using chemical conversion coatings approved by the FAA. The MRO uses a formulation of BONDERITE found in the Qualified Product List of products under performance specification MIL-DTL-81706 Chemical Conversion Materials for Coating Aluminum and Aluminum Alloys, as indicated by the FAA. Cleaned and prepared heat exchangers are dipped into the Cr(VI)-based BONDERITE (known as ALODINE) solution to dissolve and displace aluminum at the very surface with chromate. This passivated layer provides corrosion protection and improves paint adherence post process. Because the heat exchangers are comprised of many thin tubes, they retain a large amount of the Bonderite solution after processing such that there is a tremendous amount of carryover of Cr(VI) into the rinse tanks.

To find out more, read the full case study here.