Phosphate and chromate conversion coatings on aluminum have been studied by absorption-reflection Fourier Transform IR spectroscopy. Effects due to composition and temperature of the solutions used, as well as to time of immersion have been observed and discussed. In phosphate solutions aluminum hydroxides and oxyhydroxides containing acid phosphate ions are formed: they can undergo further evolution into zinc phosphate layers if the solution also contains zinc cations (e.g. commercial Bonderite). In chromate solutions, the initial steps are similar but the mechanism of further coating formation depends on the chemical composition of the solution. From acid chromate solutions, the coating contains aluminum/chromium oxyhydroxides, while from basic chromate solutions containing carbonate ions the main components are aluminum/chromium hydroxycarbonates. © 1982.
FT-IR spectroscopic study of phosphate and chromate conversion coatings on aluminum
BUSCA, GUIDO;
1982-01-01
Abstract
Phosphate and chromate conversion coatings on aluminum have been studied by absorption-reflection Fourier Transform IR spectroscopy. Effects due to composition and temperature of the solutions used, as well as to time of immersion have been observed and discussed. In phosphate solutions aluminum hydroxides and oxyhydroxides containing acid phosphate ions are formed: they can undergo further evolution into zinc phosphate layers if the solution also contains zinc cations (e.g. commercial Bonderite). In chromate solutions, the initial steps are similar but the mechanism of further coating formation depends on the chemical composition of the solution. From acid chromate solutions, the coating contains aluminum/chromium oxyhydroxides, while from basic chromate solutions containing carbonate ions the main components are aluminum/chromium hydroxycarbonates. © 1982.
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