Surface modification of Al alloys and Al-based metal-matrix composites by chemical passivation

Technical Report · Sun Jan 01 04:00:00 EST 1989

OSTI ID:6787330

Mansfeld, F; Lin, S; Kim, S; Shih, H

Chemical passivation by immersion of Aluminum 6061 and Aluminum 6061/Silicon Carbide and Al 6061/graphite metal matrix composites in a Cerous Chloride solution produces very corrosion resistant surfaces. Al 6061 which had been immersed in 1000 ppm Cerous Chloride for one week did not suffer from pitting corrosion during immersion in aerated 0.5 N Sodium Chloride for 90 days. A comparison with the corrosion resistance of Aluminum alloys treated with chromate conversion coatings shows that chemical passivation provides a valuable alternative to this process. The passivation process in CeCl3 and the corrosion process in NaCl have been monitored continuously with electrochemical impedance spectroscopy (EIS) which has been shown to be a very sensitive technique for the evaluation of these reactions. Pitting can be detected by the occurrence of a new time constant at low frequencies and a decrease of the impedance in the capacitive region. A model which describes the impedance for a surface which undergoes pitting and a fitting procedure for the analysis of the experimental EIS-data are presented.

• Research Organization: University of Southern California, Los Angeles, CA (USA). Dept. of Materials Science
• OSTI ID: 6787330
• Report Number(s): AD-A-219346/4/XAB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360105* -- Metals & Alloys-- Corrosion & Erosion
360205 -- Ceramics
Cermets
& Refractories-- Corrosion & Erosion
360604 -- Materials-- Corrosion
Erosion
& Degradation
ALKALI METAL COMPOUNDS
ALLOYS
ALUMINIUM ALLOYS
CARBIDES
CARBON
CARBON COMPOUNDS
CERIUM CHLORIDES
CERIUM COMPOUNDS
CHEMISTRY
CHLORIDES
CHLORINE COMPOUNDS
CHROMATES
CHROMIUM COMPOUNDS
COATINGS
COMPOSITE MATERIALS
CONVERSION
CORROSION PROTECTION
CORROSION RESISTANCE
ELECTROCHEMISTRY
ELEMENTAL MINERALS
ELEMENTS
GRAPHITE
HALIDES
HALOGEN COMPOUNDS
IMPEDANCE
MATERIALS
MINERALS
MODIFICATIONS
NONMETALS
OXYGEN COMPOUNDS
PASSIVATION
PASSIVITY
RARE EARTH COMPOUNDS
SENSITIVITY
SILICON CARBIDES
SILICON COMPOUNDS
SODIUM CHLORIDES
SODIUM COMPOUNDS
SPECTROSCOPY
SURFACE FINISHING
TRANSITION ELEMENT COMPOUNDS