CHARACTERIZATION OF ANODIC FILMS ON ALUMINUM FORMED IN CARBOXYLATE-BASED NONAQUEOUS ELECTROLYTE-SOLUTIONS

Anodic films were formed on aluminum at 0.5 A dm(-2) to 50 V in a 1 mo l dm(-3) triethylmethylammonium hydrogen maleate/gamma-butyrolactone s olution of varying water content (10 to 1000 ppm). The resultant films were characterized by transmission electron microscopy, Auger electro n spectroscopy, Fourier transform infrared spectroscopy, and x-ray abs orption near edge structure analysis. The thickness, chemical composit ion, and structure of the resultant barrier-type films were affected m arkedly by water content with the incorporation of electrolyte compone nts into the anodic films enhanced by decreasing water content. The fi lm formed below 200 ppm of water proved to be an electropolymerized or ganic film containing a small amount of aluminum, while the film forme d above 700 ppm of water was a different aluminum oxide containing a s mall amount of carbon. Ln the transition region between 200 and 700 pp m of water, a laminated composite film of high carbon content in the o uter layer was produced. All the films showed a new infrared peak at 1 610 cm(-1), which did not change upon annealing at 300 degrees C. This peak was assigned to an Al=0 stretching vibration. The permittivity o f the films was lowered by incorporation of organic substances into th e film material.