Tellurium (Te)-based conversion coatings grown at two different pH values were characterized by x-ray absorption near-edge structure (XANES) and Fourier transform infrared (FTIR) spectroscopy. At pH 3.5, a brown coating formed that contained reduced forms of Te as Te(0) and Te(IV). At pH 5.5, a colorless coating formed that contained traces of Te as Te(IV) and possibly Te(VI). Results suggested that iron (Fe) is soluble at low pH values and undergoes redox reactions with telluric acid, while at higher pH values, telluric acid thickens the passive film on Fe.

Subject
Acids, Steel structures, Films, Coating performance, Steel surfaces, Coatings, Absorption, Passive films, Acidity, Fourier transform infrared spectrography, Salt spray corrosion testing, Chemical conversion coatings, Paints
Keywords:
carbon steel, conversion coatings, Fourier transform infrared spectroscopy, iron, pH, phosphatizer, telluric acid, tellurium, x-ray absorption near-edge structure
NACE International
1995
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