Characterization of Conversion-Coated Aluminum Using Fourier Transform Infrared and Raman Spectroscopies

Abstract

Fourier transform infrared and Raman spectroscopies have been employed to define the molecular composition of chromium phosphate conversion coatings on aluminum. Attenuated total reflectance at 55° can be employed to probe the structure of conversion coatings present on aluminum at relatively high coating weights (≥23 mg Cr/m²). Both reflection-absorption infrared and surface-enhanced Raman spectroscopic techniques can discern the presence of conversion coatings at coverages as low as 9 mg Cr/m². On the basis of the vibrational spectra from these techniques, we have determined that hydrated chromium phosphate is the major component in these conversion coatings on aluminum. Reflection-absorption infrared and surface-enhanced Raman spectroscopies also provide a means to determine the molecular structure of the nascent oxide layer on aluminum as a function of processing conditions. Specular reflection, attenuated total reflectance at 35°, diffuse reflectance, and Raman spectroscopic methods, in general, lack the surface sensitivity necessary to probe thin (≤23 mg/m²) inorganic films on aluminum.

Keywords

FT-IR Raman spectroscopy Aluminum Conversion coating Chromium phosphate

Get full access to this article

View all access options for this article.

References

Eppensteiner

F. W.

and Jenkins

M. R

, Met. Finish. 88, 443 (1990).

Treverton

J. A.

and Davies

N. C

, Metals Technology 4, 480 (1977).

Strohmeier

B. R.

, unpublished data, Alcoa Technical Center, Pennsylvania (1990).

Miller

A. C.

and Evans

W. T

, unpublished Alcoa data, Alcoa Technical Center, Pennsylvania (1985).

For further information regarding the techniques employed in this investigation, the reader is referred to: (a) Griffiths

P. R.

and De Haseth

J. A

, Fourier Transform Infrared Spectrometry (John Wiley and Sons, New York, 1986), pp. 187–202; (b) Garrell

R. L.

, Anal. Chem. 61, 401A (1989).

Nimon

L. A.

and Korpi

G. K

, Plating 59, 421 (1972).

Suetaka

, Nippon Kinzoku Gakkaishi 32, 1233 (1968).

Schlegel

V. L.

and Cotton

T. M

, Anal. Chem. 63, 241 (1991).

Hatanaka

Fukui

Mukai

and Toyose

, Kobelco Technology Review, 28 (August 1989).

10.

Cielo

Cole

Remmers

Fairlie

and Zouikin

, Materials Evaluation 48, 898 (1990).

11.

Greenler

R. G.

, J. Phys. Chem. 44, 310 (1966).

12.

Ahern

A. M.

, unpublished Alcoa data, Alcoa Technical Center, Pennsylvania (1990).

13.

Breysse

Coudurier

Claudel

and Faure

, J. Luminescence 26, 239 (1982).

14.

Vlaev

Damyanov

and Mohamed

M. M

, Colloids and Surfaces 36, 427 (1989).

15.

Takahashi

Yamagami

Furuichi

and Nagayama

, Report of the Research Group for Functionalizing Aluminum and Its Surface Films (The Light Metal Educational Foundation, Osaka, Japan, 1988), p. 84.

16.

Kopylova

E. A.

L. P.

Zakharova

M. V.

and Klyuchnikov

Y. F

, Zhurnal Prikladnoi Khimi 47, 2336 (1974).

17.

Thomas

P. V.

Ramakrishnan

and Vaidyan

V. K

, Thin Solid Films 170, 35 (1989).

18.

Porter

M. D.

, Anal. Chem. 60, 1143A (1988).

19.

Hatch

J. E.

, Aluminum: Properties and Physical Metallurgy (American Society for Metals, Metals Park, Ohio, 1984), pp. 105–106.

20.

Cooney

R. P.

Howard

M. W.

Mahoney

M. R.

and Mernaugh

T. P

, Chem. Phys. Lett. 79, 459 (1981).

21.

Hardcastle

F. D.

and Wachs

I. E

, J. Molecular Catalysis 46, 173 (1988).

22.

England

W. A.

Jenny

S. N.

and Greenhalgh

D. A

, J. Raman Spectrosc. 15, 156 (1984).

23.

Graves

P. R.

, J. Chem. Soc., Chem. Commun., 1418 (1986).

24.

Molt

Egelkraut

and Gottwald

K.-H

, Mikrochim. Acta [Wien] II, 62 (1988).

25.

Mansour

T. M.

, Materials Evaluation 41, 302 (1983).

26.

Cheever

G. D.

, J. Coating Technology 50, 78 (1978).

27.

Nyquist

R. A.

and Kagel

R. O

, Infrared Spectra of Inorganic Compounds (Academic Press, New York, 1971), pp. 216–217.