Molybdate Coatings for Protecting Aluminum Against Corrosion

Calle, Luz Marina; MacDowell, Louis G.

Conversion coatings that comprise mixtures of molybdates and several additives have been subjected to a variety of tests to evaluate their effectiveness in protecting aluminum and alloys of aluminum against corrosion. Molybdate conversion coatings are under consideration as replacements for chromate conversion coatings, which have been used for more than 70 years. The chromate coatings are highly effective in protecting aluminum and its alloys against corrosion but are also toxic and carcinogenic. Hexavalent molybdenum and, hence, molybdates containing hexavalent molybdenum, have received attention recently as replacements for chromates because molybdates mimic chromates in a variety of applications but exhibit significantly lower toxicity. The tests were performed on six proprietary formulations of molybdate conversion coatings, denoted formulations A through F, on panels of aluminum alloy 2024-T3. A bare alloy panel was also included in the tests. The tests included electrochemical impedance spectroscopy (EIS), measurements of corrosion potentials, scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS), and x-ray photoelectron spectroscopy (XPS).

Document ID

20110014690

Acquisition Source

Kennedy Space Center

Document Type

Other - NASA Tech Brief

External Source(s)

http://www.techbriefs.com/component/content/article/159

Authors

Date Acquired

August 25, 2013

Publication Date

January 1, 2005

Publication Information

Publication: NASA Tech Briefs, January 2005

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Report/Patent Number

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Public

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