Processing and properties of chromate-free conversion coatings on aluminum

Conference · Sat Dec 31 04:00:00 EST 1994

OSTI ID:10108372

Buchheit, R G; Drewien, C A; Martinez, M A ^[1]; Stoner, G E ^[2]

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1. Sandia National Labs., Albuquerque, NM (United States)
2. Virginia Univ., Charlottesville, VA (United States). Dept. of Materials Science and Engineering

A conversion coating method has been developed based on precipitation of Li{sub 2}[Al{sub 2}(OH){sub 6}]{sub 2}{center_dot}CO{sub 3}{center_dot}3H{sub 2}O from alkaline lithium salt solutions. The process is procedurally similar to chromate conversion coating but does not use or produce hazardous chemicals. The coating that forms is polycrystalline, continuous and conformal. The coating meets the MIL-C-5541E corrosion resistance, electrical contact resistance and paint adhesion requirements for certain aluminum alloys, but does not match the levels of performance exhibited by chromate conversion coatings. In this paper, methods for producing the coating are described. Corrosion resistance has been characterized using electrochemical impedance spectroscopy and salt spray exposure. The structural, compositional and property changes attending post-coating thermal exposure are discussed. Performance in standardized corrosion, electrical and paint adhesion tests is also presented.

• Research Organization: Sandia National Labs., Albuquerque, NM (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States); Virginia Univ., Charlottesville, VA (United States)
• DOE Contract Number: AC04-94AL85000
• OSTI ID: 10108372
• Report Number(s): SAND--94-3141C; CONF-950304--8; ON: DE95004768; BR: GB0103012
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360105
360601
ADHESION
ALUMINIUM ALLOYS
COATINGS
CORROSION AND EROSION
CORROSION PROTECTION
CORROSION RESISTANCE
LITHIUM COMPOUNDS
PRECIPITATION
PREPARATION AND MANUFACTURE
SALTS