A new chemical treatment for aluminum alloys with a dilute solution of sodium oxalate was found to improve the corrosion resistance when compared with the conventional boehmite treatment with water and/or triethanolamine solution. When a specimen is treated with the sodium oxalate solution, porous film about 1 μm thick deposits on the alloy surface. The film consists of pseudo-boehmite with a high water content and a small amount of oxalate. The corrosion potential of the treated alloy moves in the negative direction compared with the untreated alloy while the pitting potential moves in the positive, and hence the specimen exhibits higher resistance to pitting corrosion in sodium chloride solution containing cupric ion. The high corrosion resistance is attributed to the diminution of oxygen permeation through the oxide film.

Subject
Ions, Corrosion resistant alloys, Metal surfaces, Aluminum, Sodium chloride solution, Solutions, Sodium, Pitting, Immersion, Aluminum alloys, Alloys, Corrosion potential, Chemical treatment
Keywords:
aluminum alloy, chemical treatment, pitting corrosion
National Association of Corrosion Engineers
1990
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