Chromate Conversion Coatings on 2024 Al Alloy

Hughés, A.E.; Taylor, Roger; Hinton, Bruce

doi:10.1002/(sici)1096-9918(199704)25:4<223::aid-sia225>3.0.co;2-d

Cited by 151 publications

(114 citation statements)

References 7 publications

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“…25 The driving force for Cr(III) deposition comes from the rise in pH near the metal surface [26][27][28][29] caused by redox reactions on the heterogeneous, heat-treated alloy. 30 The oxidation reaction occurs on Al-rich matrix (similar to our alloy substrates) accompanied by proton reduction on Cu-rich inclusions, which are absent in our films.…”

Section: Film Structure Of Tcp Immersion Filmsmentioning

confidence: 99%

Morphology and Mechanism of Benign Inhibitors

Schaefer¹,

Wang²,

Xin³

2012

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Section: Film Structure Of Tcp Immersion Filmsmentioning

confidence: 99%

Morphology and Mechanism of Benign Inhibitors

Schaefer¹,

Wang²,

Xin³

2012

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“…Cr(VI) Cr(III) 5,7,8) Cr ( Cr(VI) (DPC) 9,10) Cr(VI) 11,12) Cr(VI) X (XPS) [13][14][15] Tetsu-to-Hagané Vol. 95 (2009) [20][21][22][23][24] Cr K X XANES…”

Section: Eu Elv Rohsmentioning

confidence: 99%

Analysis of Valence for Chromate Conversion Coatings Using Laboratory XAFS Spectrometer and a Comparison with X-ray Photoelectron Spectroscopy

Miyauchi¹,

Yamamoto²,

Kitagaki³

et al. 2009

Tetsu-to-Hagane

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Synopsis :We performed a nondestructive and in laboratory evaluation technique of hexavalent chromium (Cr(VI)) in chromate conversion coatings using a laboratory X-ray absorption fine structure (XAFS) spectrometer equipped with W anode X-ray tube. The recorded XANES spectrum of a chromate conversion coating sample with fluorescence mode possessed the Cr-K X-ray absorption edge. We have obtained calibration curves of the ratio of Cr(VI)/Cr(III) by the height of pre-edge peak and the Cr-K X-ray absorption edge energy of the reference samples prepared by Cr 2 O 3 (Cr(III)) and CrO 3 (Cr(VI)) particle reagents. The calibration curves showed the high correlation coefficients such as 1.00 for the height of pre-edge peak and 0.99 for the value of the energy on the Cr-K X-ray absorption edge. The ratio of Cr(VI)/Cr(III) in the chromate conversion coating has also been evaluated by the X-ray photoelectron spectroscopy (XPS) and 1,5-diphenyl-carbazide absorption spectrometry (DPC) methods. The ratio of Cr(VI)/Cr(III) evaluated by the laboratory XAFS spectrometer was almost identical to that by XPS method.

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“…5 Chromate conversion coatings (CCC) have been subjected to intensive study over the past decades due to the effective corrosion protection they confer to Al alloys and the desire to develop an effective and environment-friendly replacement. [6][7][8] The composition and structure of CCC formed on pure Al and Al alloys have been investigated extensively using a variety of analytical tools. However, this work deals with commercially available Cr(VI)-free alternatives.…”

Section: Introductionmentioning

confidence: 99%

Alternative corrosion protection pretreatments for aluminum alloys

et al. 2017

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Aluminum alloys are extensively used in space programs for both structural and nonstructural applications. As is well known, the corrosion resistance of these alloys is quite limited and anticorrosion treatment is needed. Currently, the treatment most often used for improving the corrosion resistance of aluminum alloys is chromate (CrVI-based) conversion coatings (CCC). Due to the high environmental impact of these compounds, the REACH Regulation of the European Union decided to limit/restrict the use of hexavalent chromium. A sunset date of mid-2017 has been already set. For the time being, many chromatefree alternative products are available, but they have been found to be significantly inferior in terms of corrosion protection performances with respect to the chromate options. In this regard, there is a great need to develop high-performance hexavalent chromiumfree anticorrosion coatings with low environmental impact and conformity with the EU regulations. The European Space Agency (ESA) is currently involved in a frame contract with Instituto de Soldadura e Qualidade (ISQ) that is currently ongoing. The objective of this study is to evaluate the anticorrosion behavior of the different alternative pretreatments applied to the most used aluminum alloys. The outcome of this activity will be the identification and the optimization of the most promising anticorrosion pretreatment. Several commercial Cr(VI)-free processes were applied onto aluminum alloys (2024-T3 and 2024-T81) used in the construction of ESA spacecraft in order to investigate their anticorrosive properties compared with Alodine 1200, a widely used conventional CCC. One of these commercial processes presented good anticorrosion performance, even better than Alodine 1200, and these results are presented in this paper. Salt spray resistance is included in the testing program as well as metallurgical coating evaluations that include microscopy observations before and after testing and electrochemical impedance spectroscopy in order to evaluate surface and microstructural modifications due to degradation mechanisms. Further studies must be performed with this promising alternative, modifying application parameters in order to achieve improved corrosion protection efficiency.

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Chromate Conversion Coatings on 2024 Al Alloy

Cited by 151 publications

References 7 publications

Morphology and Mechanism of Benign Inhibitors

Morphology and Mechanism of Benign Inhibitors

Analysis of Valence for Chromate Conversion Coatings Using Laboratory XAFS Spectrometer and a Comparison with X-ray Photoelectron Spectroscopy

Alternative corrosion protection pretreatments for aluminum alloys

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