Characterization of tellurium-based conversion coatings by X-ray absorption near-edge structure and Fourier transform infrared spectroscopy
- Calgon Vestal Labs. Inc., St. Louis, MO (United States)
- Brookhaven National Lab., Upton, NY (United States)
To improve paint adhesion and extend protection of carbon (C) steel surfaces exposed to a variety of environmental conditions, these surfaces typically are phosphatized. These iron phosphate-based conversion coatings require a chromic acid sealing rinse for enhanced performance. However, the use of chromate increasingly is being limited because of the safety problems of handling carcinogenic chromate solutions and because of environmental concerns. Tellurium-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 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.
- Research Organization:
- Brookhaven National Lab. (BNL), Upton, NY (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC02-76CH00016
- OSTI ID:
- 187053
- Journal Information:
- Corrosion, Vol. 51, Issue 1; Other Information: PBD: Jan 1995
- Country of Publication:
- United States
- Language:
- English
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