Reflectance spectroscopy (0.03 to 6 eV) of Cr3+ and Cr(VI) products of chromate conversion coatings

Lenglet, M.; Petit, F.; Malvault, J. Y.

doi:10.1002/pssa.2211430220

Cited by 7 publications

(3 citation statements)

References 10 publications

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“…6 An important feature of a CCC is "self-healing," in which a scratch or defect in a mature CCC is protected without further treatment.7-9 Self-healing may be caused by migration of soluble Cr(VI) species incorporated into the CCC. 19 '11 The mechanism of corrosion protection by CCC films has been attributed to several effects, including inhibition of oxygen reduction kinetics,11 blocking of active pores by Cr(III) formed from Cr(VI) reduction,112 or an increase in film resistance. 13 The CCC formed on aluminum aircraft alloys is amorphous and not subject to analysis by X-ray diffraction techniques.…”

Section: Introductionmentioning

confidence: 99%

Chemistry of a Chromate Conversion Coating on Aluminum Alloy AA2024‐T3 Probed by Vibrational Spectroscopy

Xiao

McCreery

1998

J. Electrochem. Soc.

181

162

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Infrared and Raman spectroscopy were used to characterize a chromate conversion coating (CCC) on 2024-T3 aluminum aircraft alloy with a long range objective of determining the anticorrosion mechanism of the CCC. Spectra were compared to those from synthetic mixed oxides of aluminum, Cr(III), and Cr(VI) made by treating pure reagents with NaOH. The Fourier transform infrared (FTIR) and Raman spectra of the CCC showed similar behavior to the chromium Ill/VI mixed oxide for both the initial materials and after heat-treatment. Analysis of the CCC and chromium mixed oxide by UV-vis spectroscopy indicated that both have a 3:1 ratio of Cr(III) to Cr(VI). When the chromium mixed oxide was immersed in pH 4 HNO3, the ratio of released H to released Cr(VI) ranged from 0.98 to 1.07. In addition, a compound with a Raman spectrum very similar to that of a CCC was formed by a reaction of Cr(III) hydroxide with Cr2O2, CrO2, or the Alodine chromating bath. The results indicate a strong structural similarity between the Cr-mixed oxide and a major component of the CCC. A likely structure for this common material involves covalent bonding between polymeric Cr(III) hydroxide and Cr202 or CrO . This mixed oxide structure may hydrolyze to release H and soluble chromate.

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Section: Introductionmentioning

confidence: 99%

Chemistry of a Chromate Conversion Coating on Aluminum Alloy AA2024‐T3 Probed by Vibrational Spectroscopy

Xiao

McCreery

1998

J. Electrochem. Soc.

181

162

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“…anions. [22][23][24] The band near 1126 cm 21 can be attributed to SO 4 22 in the Cr(III)-A coating 25 and PO 4 32 in the Cr(III)-B coating. 24 The vibration bands at 580, 642 and 836 cm 21 are attributable to Cr(III)-O x .…”

Section: Morphology and Thickness Of Coatingsmentioning

confidence: 99%

“…98 V(SCE). The breakdown potential (defined as the potential at which the anodic current exceeds 10 25 A cm 22 ) is between 20 . 91 and 20 .…”

Section: Composition Of Coatingsmentioning

confidence: 99%

Investigation of Cr(III) Based Conversion Coatings on Electrogalvanised Steel

Zhang

Bos

Sloof

et al. 2004

Surface Engineering

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The corrosion behaviour of Cr(III) based conversion coatings on electrogalvanised steel was studied using polarisation and electrochemical impedance spectroscopy measurements in 0 . 01M NaCl solution (pH 6). The Cr(III) based conversion treatments were carried out in two different commercial trivalent chromium baths (pH 1 . 8-2 . 0). With an immersion time of 1 min, the thickness of the first type of Cr(III) based coating (blue) was about 94 nm and the thickness of the second type of coating (iridescent yellow) was about 250 nm; these thicknesses were determined by spectroscopic ellipsometry. As a comparison, a Cr(VI) based coating on electrogalvanised steel was also studied. The morphologies and compositions of the coatings were investigated by means of scanning electron microscopy, Fourier transform infrared spectroscopy and Auger electron spectroscopy. The Cr(III) coatings contained mainly a mixture of zinc oxides and chromium oxides/ hydroxides, and no Cr(VI) was detected in these coatings. The polarisation measurements in NaCl solution showed a retarded cathodic reaction for both the Cr(III) and the Cr(VI) based coatings. The corrosion resistance of the thicker Cr(III) coating was greater than that of the thinner Cr(III) coating. However, in the cases studied, the Cr(III) coatings still did not inhibit the corrosion of the electrogalvanised steel as effectively as did the Cr(VI) based coatings. The reason may be that the Cr(III) coatings do not possess the 'self-healing' properties that the Cr(VI) based coatings do. SE/S295

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Cathodic reduction and infrared reflectance spectroscopy of basic copper(II) salts on copper substrate

et al. 1995

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Reflectance spectroscopy (0.03 to 6 eV) of Cr3+ and Cr(VI) products of chromate conversion coatings

Cited by 7 publications

References 10 publications

Chemistry of a Chromate Conversion Coating on Aluminum Alloy AA2024‐T3 Probed by Vibrational Spectroscopy

Chemistry of a Chromate Conversion Coating on Aluminum Alloy AA2024‐T3 Probed by Vibrational Spectroscopy

Investigation of Cr(III) Based Conversion Coatings on Electrogalvanised Steel

Cathodic reduction and infrared reflectance spectroscopy of basic copper(II) salts on copper substrate

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