An Air Force pollution prevention initiative ''Demonstration of a non-chromate conversion coating for ion vapor deposition (IVD) aluminum''

The goal of this project is to demonstrate a non-chromate alternative to chromate conversion coatings currently used for ND aluminum-coated parts. When successful, this effort will improve the work environment at Air Force Air Logistics Centers (ALCs), reduce hazardous waste production from the IVD aluminum/conversion coating process, and virtually eliminate the need for expensive pollution control equipment. This alternative technology will replace the chromate conversion coating, comply with MIL-C-83488, and reduces hazardous waste generation and disposal. Stringent environmental and occupational health regulations for Air Force electroplating facilities are restricting pollutant discharges from the ALCs and have escalated the cost of waste disposal. Chromate conversion coatings contain hexavalent chrome, a known human carcinogen. Demonstration and validation of alternative conversion coatings for IVD aluminum are needed to ensure that coatings for Air Force aircraft parts will meet performance criteria in military specifications in an environmentally friendly manner. The Air Force ALCs are eliminating the use of cadmium processing for aircraft maintenance and overhaul in order to eliminate hazardous cadmium wastestreams. With the exception of a sacrificial, corrosion-resistant barrier, the replacement process, ion vapor deposition (IVD) of aluminum, eliminates many of the environmental problems associated with cadmium processing. The traditional corrosion barrier used with the IVD process uses a chromate conversion coating to provide additional corrosion protection and an improved base for paint or primer adhesion. The Air Force (Armstrong Laboratory, Environics Directorate) entered a contract with McDonnell Douglas Aerospace-East (MDA-E) in 1993 to identify a non-chromate coating alternative to traditional chromate conversion coating for IVD aluminum A number of conversion coating candidates were tested for adhesion and corrosion protection. In addition, the candidate coatings were subjected to a number of performance tests which included electrical resistance, adhesion, corrosion, humidity resistance, and fluid resistance. Results were then compared with a baseline chromate conversion coated panel. Following the full test cycle, the best candidate non-chromate conversion coatings were selected for the Armstrong Laboratory's demonstration and validation project which began in May, 1996. Acurex Environmental Corp. is the contractor performing the demonstration and WR-ALC, Robins Air Force Base, Georgia is the demonstration facility.