Grantee Research Project Results
Final Report: New Environmentally Benign Heteropolymolybdate Conversion Coatings for Aluminum Alloys
EPA Contract Number: 68D98127Title: New Environmentally Benign Heteropolymolybdate Conversion Coatings for Aluminum Alloys
Investigators: Minevski, Zoran
Small Business: Lynntech Inc.
EPA Contact:
Phase: I
Project Period: September 1, 1998 through March 1, 1999
Project Amount: $70,000
RFA: Small Business Innovation Research (SBIR) - Phase I (1998) RFA Text | Recipients Lists
Research Category: SBIR - Pollution Prevention , Nanotechnology , Pollution Prevention/Sustainable Development , Small Business Innovation Research (SBIR)
Summary/Accomplishments (Outputs/Outcomes):
Use of chemical conversion coatings on aluminum alloys to achieve long-term corrosion resistance of painted spacecraft and aircraft structures have found widespread military and commercial applications. With increasing environmental regulations, the use of chemical conversion coatings that do not contain harmful chemicals is of particular interest to DOD, NASA, and other federal agencies. Conventional baths currently in use for conversion coatings contain chromates, which are highly toxic and known carcinogens. Alternatives for chromate conversion coatings which exhibit the same corrosion resistance as chromate coatings and are formulated from environmentally acceptable chemicals are needed.Lynntech, Inc. has developed and tested during this Phase I research a new type of heteropolymolybdate-based conversion coating that provides both features. Tests demonstrate an exceptional corrosion resistance of the new coating prepared from formulations consisting of heteropolymolybdates and several important additives. Some coatings outperformed the chromate-based conversion coatings in electrochemical corrosion resistance tests and passed a standard 14 day salt fog test.
Key advantages of heteropolymolybdate conversion coatings are:
Environmentally friendly (coatings are inorganic and do not contain chemicals or materials that are hazardous, toxic, or give rise to health and safety concerns),
Excellent protection (protects 2024-T3 and 6061-T6 aluminum alloys for at least 336 hours of exposure in a salt fog chamber according to ASTM B117),
Versatile (can be applied by dipping, painting or spraying methods),
Simple application (short treatment times, can be applied at room temperature, and is compatible with existing cleaning and pretreatment procedures)
Low cost (Only commercially available chemicals and materials are used in the conversion coating formulations. These chemicals can easily be adapted into existing application methods, and none of the chemicals require special storage provisions).
Results of this Phase I research establish a sound technical feasibility for the proposed conversion coating and have shown the ability of heteropolymolybdates to effectively promote the formation of a thick, corrosion protective coating of hexavalent molybdenum and aluminum oxides. In addition, it has been shown that, even in the reduced state, molybdenum ions remain in heteropolymolybdate clusters. These reduced clusters have been observed to oxidize slowly in air from Mo4+ to Mo6+, which promotes the self-healing process.
The cost of the process of the heteropolymolybdate conversion coating is attractive when compared to that of existing chromate-based conversion coatings since the need for toxic waste disposal, special handling, and human protection is greatly reduced. The heteropolymolybdate conversion coating, when fully developed, would have wide spread application in the treatment of a variety of aluminum alloys (e.g. 2024, 6061, and 7075) and will effect installations of DOD (e.g. Navy: Std Missile, Phalanx, RAM, Tomahawk; Air Force: ACM, AMRAAM; Army: TOW, Stinger), NASA, DOD prime contractors (Boeing, Grumman, Northrop, Rockwell, Lockheed, Hughes), and civil industry applications (boilers, air conditioners, aluminum construction materials).
Initial parameters have been identified to recommend further studies and technology demonstration for this environmentally safe, corrosion protective, and cost effective process under a possible Phase II follow-on project.
Journal Articles:
No journal articles submitted with this report: View all 1 publications for this projectSupplemental Keywords:
Sustainable Industry/Business, RFA, Air, Scientific Discipline, Toxics, National Recommended Water Quality, Technology for Sustainable Environment, Chemical Engineering, Chemistry, Sustainable Environment, HAPS, Environmental Chemistry, 33/50, Engineering, Chemistry, & Physics, Chemistry and Materials Science, cleaner production/pollution prevention, Environmental Engineering, chromium & chromium compounds, clean technology, Chromium, pollution prevention, coatings, heteropolymolybdate, heteropolymolybdate conversion coatings, Chromium Compounds, conversion coating, cleaner production, alternative coatingsSBIR Phase II:
New Environmentally Benign Heteropolymolybdate Conversion Coatings for Aluminum Alloys | Final ReportThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.