Characterization of chromate conversion coatings on zinc using XPS and SKPFM

Zhang, X.; Sloof, W.G.; Hovestad, A.; Westing, E.P.M. van; Terryn, Herman; Wit, J.H.W. de

doi:10.1016/j.surfcoat.2004.08.196

Cited by 92 publications

(53 citation statements)

References 22 publications

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“…[34,35] Then, an increase in the number of microcracks, porosity, and thickness can appear in the CCCs on Fe-Al-Zn and Fe-Zn alloys when the dipping time is longer than 10 seconds. These results are also in agreement with the results obtained by Zhang et al, [36] who additionally suggested that for Fe-Zn alloys, the chromate layer displays cathodic inhibition.…”

Section: B Microstructural Characterization Of Cccssupporting

confidence: 93%

“…[36] However, from the SEM measurements, it was clear that the treatment thickness increases with the immersion time. From these micrographs, the semiquantitative measurements of the chromate film thicknesses ranged from 900 to 1500 nm, which are higher than those reported in the literature and could explain the high light dispersion.…”

Section: B Microstructural Characterization Of Cccsmentioning

confidence: 98%

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Synthesis and Characterization of Chromate Conversion Coatings on GALVALUME and Galvanized Steel Substrates

Domínguez‐Crespo

Onofre-Bustamante

Torres‐Huerta

et al. 2009

Metall Mater Trans A

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The morphology, composition, and corrosion performance of chromate conversion coatings (CCCs) formed on GALVALUME (Fe-Al-Zn) and galvanized steel (Fe-Zn) samples have been studied, and different immersion times (0, 10, 30, and 60 seconds) have been compared. The coated surfaces were analyzed using light microscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical measurements in a NaCl solution (3 wt pct). The electrochemical measurements were carried out using the polarization resistance, Tafel, and ac impedance methods. A nonuniform growth of the CCCs having a porous morphology and cracks that appear extended to the base metal was observed. The XRD patterns show that the coatings mainly consist of CrO 3 , Cr 2 O 3 , and traces of Cr 2 O 7 À2 . The electrochemical results show that GALVALUME presents a better behavior than that of the galvanized steel alloys at each dipping time. The SEM micrographs show that the galvanized steel treatments resulted in the formation of a more uniform film, but their protection barrier broke down faster than that of the GALVALUME samples in contact with the aggressive media. The samples that underwent the lowest degree of dissolution were those with a dipping time of 30 seconds. The difference in the corrosion protection given by the two substrate types could be attributed to the structural properties, grain size, composition, and roughness, which affect oxygen diffusion.

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Section: B Microstructural Characterization Of Cccssupporting

confidence: 93%

Section: B Microstructural Characterization Of Cccsmentioning

confidence: 98%

Synthesis and Characterization of Chromate Conversion Coatings on GALVALUME and Galvanized Steel Substrates

Domínguez‐Crespo

Onofre-Bustamante

Torres‐Huerta

et al. 2009

Metall Mater Trans A

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“…Similar results were reported by Worn Park et al [43] in the case of the photoreduction of Ce(IV) to Ce(III) in CeO 2 : these authors have observed that the extent of reduction increased rapidly with time up to approximately 180 min, whereas for longer analysis times, the change in reduced CeO 2 amount was less obvious and the reduced fraction stabilizes around 25%. Concerning the photoreduction of Cr(VI) in chromate conversion coatings on zinc substrates, Zhang et al [44] have shown, following the Cr2p 3/2 photoelectron peak located at 579.0 eV, that the Cr(VI) concentration was around 40 at.% after the first measurement (about 45 min of X-ray exposure) and afterwards, the reduction rate became slow and the Cr(VI) amount represents about 33 at.% of the total chromium. Wallbank et al [45] have reported similar conclusions in the case of CuF 2 photoreduction (Cu 2+ → Cu 0 ).…”

Section: X-ray Photoelectron Spectroscopymentioning

confidence: 99%

X‐ray photoreduction of U(VI)‐bearing compounds

Mercier‐Bion

Drot

Ehrhardt

et al. 2011

Surface & Interface Analysis

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During XPS analysis, the soft X-ray-induced reduction of metals such as Cr(VI) and Ce(IV) in oxides has been reported in the literature and some mechanisms have been proposed to explain this phenomenon. The reduction of U(VI) by the beam during X-ray Photoelectron Spectroscopy has been already reported in the literature but only for U(VI) sorbed or precipitated onto solids with reducing properties (as micas or pyrites) for whose Fe(II) can also induce the reduction of U(VI), or onto TiO2 whose the photocatalytic properties are well known. The objective of this paper is to investigate the effects of X-ray beam on U(VI) bulk compounds (UO3, UO2(OH)2, (UO2)2SiO4, UO2(CH3COO)2 and UO2C2O4). Successive U4f, U5f, C1s XPS spectra were recorded and compared as a function of the irradiation time. The XPS photoreduction of U(VI) into U(IV) is only observed for uranyl compounds containing organic matter (uranyl acetate and uranyl oxalate). Considering the evolution of the C1s signal during the X-ray irradiation, a significant decrease of the C O component simultaneously to the U(VI) reduction is observed, which suggests a desorption of CO or other volatile organic products from the solid surface. All these results on U(VI) bulk compounds indicate the important role of organic carbon species in the photoreduction process and to explain these observations, a photoreduction mechanism has been suggested

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“…For the Cr(III) coatings, no Cr(VI) peak was observed near 579.2 eV, which means that there is no Cr(VI) in the layer. The Cr 2p 3/2 curves were fitted for chromium in the form of Cr 2 O 3 (576.3 ± 0.2 eV), Cr(OH) 3 or CrOOH (577.4 ± 0.2 eV) and Cr(VI) (579.2 ± 0.2 eV) in the chromate layer (12)(13)(14)(15). The fitting results show that the ratio of Cr(VI) to total Cr is about 0.4.…”

Section: Methodsmentioning

confidence: 99%

Drying Effects on Corrosion Properties of Cr(VI)- and Cr(III)- Treated Electrogalvanized Steel

Zhang¹,

Bos

Sloof

et al. 2006

ECS Trans.

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Drying effects on corrosion performance of Cr(VI)-and Cr(III)-treated electro-galvanized steel have been studied in NaCl solution using potentiodynamic measurements and electrochemical impedance spectroscopy (EIS). The Cr(VI) and the Cr(III) treated specimens were dried at three different temperatures: 60, 110 and 210°C. The surface layers were investigated using SEM, AES and XPS. The results show that the drying temperature not only affects the morphology of the surface layer, but also changes the chromium oxidation states in the layer. The corrosion protection given to the EG steel by Cr(VI) and Cr(III) pretreatments can be severely reduced if the pretreated surfaces are heated above 110°C. Both types of coating undergo some dehydration during heat treatments, which is undesirable for good corrosion protection. For Cr(VI) coatings, additional degradation mechanisms include widening of the cracks in the coating, and reduction of Cr(VI) to the Cr(III) oxidation state.

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Characterization of chromate conversion coatings on zinc using XPS and SKPFM

Cited by 92 publications

References 22 publications

Synthesis and Characterization of Chromate Conversion Coatings on GALVALUME and Galvanized Steel Substrates

Synthesis and Characterization of Chromate Conversion Coatings on GALVALUME and Galvanized Steel Substrates

X‐ray photoreduction of U(VI)‐bearing compounds

Drying Effects on Corrosion Properties of Cr(VI)- and Cr(III)- Treated Electrogalvanized Steel

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