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

Zhang, X.; Bos, C. van den; Sloof, Willem G.; Hovestad, A.; Terryn, Herman; Wit, J.H.W. de

doi:10.1149/1.2215586

Cited by 3 publications

(5 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In Figure , typical curve-fitted Cr 2p core level spectra of 3% and 15% Cr/Co 3 O 4 catalysts are shown. Observed Cr 2p 3/2,1/2 peaks around 576.2 and 585.9 eV with 9.7 eV spin–orbit separation correspond to Cr 3+ species. , Weak component peaks at 578.6 and 588.3 eV with 9.7 eV spin–orbit separation can be attributed to either Cr 3+ species in Cr(OH) 3 or Cr 6+ species. , The possibility of formation of hydroxide species may be higher as a component peak related to hydroxide species is observed in O 1s core level spectra (discussed later). It has been noticed that surface concentrations of hydroxide/Cr 6+ are observed to be in 10–23% in these catalysts.…”

Section: Resultsmentioning

confidence: 95%

“…43,44 Weak component peaks at 578.6 and 588.3 eV with 9.7 eV spin−orbit separation can be attributed to either Cr 3+ species in Cr(OH) 3 or Cr 6+ species. 45,46 The possibility of formation of hydroxide species may be higher as a component peak related to hydroxide species is observed in O 1s core level spectra (discussed later). It has been noticed that surface concentrations of hydroxide/ Cr 6+ are observed to be in 10−23% in these catalysts.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Low-Temperature CO Oxidation over Combustion Made Fe- and Cr-Doped Co₃O₄ Catalysts: Role of Dopant’s Nature toward Achieving Superior Catalytic Activity and Stability

et al. 2017

View full text Add to dashboard Cite

Co3O4 with a spinel structure shows unique activity for CO oxidation at low temperature under dry conditions; however the active surface is not very stable. In this study, two series of Fe- and Cr-doped Co3O4 catalysts were prepared by a single-step solution combustion technique. Fe was chosen because of its redox activity corresponding to the Fe2+/Fe3+ redox couple and compared to Cr, which is mainly stable in the Cr3+ state. The catalytic activity of new materials for low-temperature CO oxidation was correlated to the nature of the dopant. As a function of dopant concentration, the temperature corresponding to the 50% CO conversion (T 50) demonstrated significant differences. The maximal activity was achieved for 15% Fe-doped Co3O4 with T 50 of −85 °C and remained almost constant up to 25% Fe. In the case of Cr, the activity was observed to be maximum for 7% of Cr with T 50 of −42 °C and significantly decreased for higher Cr loadings. Similarly, there was a contrasting behavior in catalyst stability too. 100% CO conversion was achieved below −60 °C for 15% Fe/Co3O4 catalyst and remained unchanged even after calcination at 600 °C. In contrast, Co3O4 or 15% Cr/Co3O4 catalysts strongly deactivated after the same treatment. These differences were correlated to the oxidation states, coordination numbers, the nature of surface planes, and the redox properties. We observed that both Cr and Fe were typically present in the +3 oxidation state, occupying octahedral sites in the spinel structure. The catalysts were mainly exposed to (111) and (220) planes on the surface. H2-TPR indicated clear differences in the redox activity of materials due to Fe and Cr substitutions. The reducibility of surface Co3+ species remained similar in all Fe-doped Co3O4 catalysts in contrast to nonreducible Cr-doped analogs, which shifted the reduction temperature to the higher values. As the Fe3+/Fe2+ redox couple partly substituted the Co3+/Co2+ redox couple in the spinel structure, similar bond strength of Fe–O keep redox activity of Co3+ species almost unchanged leading to higher activity and stability of Fe/Co3O4 catalysts for low-temperature CO oxidation. In contrast, nonreducible Cr3+ species characterized by strong Cr–O bond substituting active Co3+ sites can make the Cr/Co3O4 surface less active for CO oxidation.

show abstract

Section: Resultsmentioning

confidence: 95%

Section: Resultsmentioning

confidence: 99%

Low-Temperature CO Oxidation over Combustion Made Fe- and Cr-Doped Co₃O₄ Catalysts: Role of Dopant’s Nature toward Achieving Superior Catalytic Activity and Stability

et al. 2017

View full text Add to dashboard Cite

show abstract

“…The Cr 2p 3/2,1/2 peaks found at 576.2 and 585.8 eV with 9.6 eV spin–orbit separation are attributed to Cr 3+ species . The low-intensity component peaks at 578.7 and 588.5 eV with 9.8 eV spin–orbit separation correspond to either Cr 3+ species in Cr(OH) 3 or Cr 6+ species. , The formation of hydroxide species may be more plausible, as a component peak associated with hydroxide species is found in the O 1s core level spectrum. However, it is evident from XPS studies that Cr 3+ species are the dominant species in the CoCr 2 O 4 catalyst.…”

Section: Resultsmentioning

confidence: 97%

“…Here, surface concentrations of Fe 2+ and Fe 3+ species or Cr 6+ species. 55,56 The formation of hydroxide species may be more plausible, as a component peak associated with hydroxide species is found in the O 1s core level spectrum. However, it is evident from XPS studies that Cr 3).…”

Section: Resultsmentioning

confidence: 99%

Ultra-Low-Temperature CO Oxidation Activity of Octahedral Site Cobalt Species in Co₃O₄ Based Catalysts: Unravelling the Origin of the Unique Catalytic Property

et al. 2019

View full text Add to dashboard Cite

Co 3 O 4 with spinel structure shows CO oxidation activity at very low temperature under dry conditions. This study aims at finding the origin of the unique catalytic activity of Co species in Co 3 O 4 based oxides. Although, octahedral site Co 3+ species have been reported to be active in Co 3 O 4 based catalysts, there is no solid explanation as to why Co is so special as compared with other metals like Fe having similar redox states. In this study, mainly, three model spinel catalysts including MnCo 2 O 4 , MnFe 2 O 4 , and CoCr 2 O 4 have been chosen. A detailed analysis of bulk and crystal surface structure, surface properties of the catalysts, and redox properties of the active metals has been performed to understand the unusual catalytic activity. Low-temperature CO oxidation activity decreases in the following order: MnCo 2 O 4 ≫ MnFe 2 O 4 > CoCr 2 O 4 . It indicates that the Co 2+ species in a tetrahedral site (in CoCr 2 O 4 ) remains inactive for lowtemperature catalytic activity, while Co 3+ in an octahedral site (in MnCo 2 O 4 ) is active in Co 3 O 4 based catalysts. This result is corroborated with CoFe 2 O 4 which shows a higher activity than CoCr 2 O 4 , as it has partial occupation of the octahedral site. Fe, being a weak redox metal, does not show low-temperature activity, although crystallite facets of MnCo 2 O 4 and MnFe 2 O 4 catalysts are predominantly exposed in the (100) and (110) lattice planes, which contain quite similar concentrations of Co 3+ and Fe 3+ species in both. The intensity of the redox peak for CO oxidation involving a Co 3+ /Co 2+ couple in MnCo 2 O 4 indicates a highly favorable reaction, while a nonresponsive behavior of Co species is observed in CoCr 2 O 4 . As expected, MnFe 2 O 4 is proven to be weak, giving a much lower intensity of electrochemical CO oxidation. Both CO-and H 2 -TPR indicate a much higher reducibility of Co species in MnCo 2 O 4 as compared with Co species in CoCr 2 O 4 or Fe in MnFe 2 O 4 .

show abstract

“…Our work does not demonstrate the link between the susceptibility to cracking of the conversion layer under vacuum and its corrosion resistance, as has been established by other researchers. 25,33,65,66 Laget et al 33 studied chromate conversion coating, and concluded that the dehydration of the coatings explains the losses in corrosion resistance observed after aging. Heller et al 65 found that inhibiting cracking improves the corrosion resistance of cerium conversion coatings but that elimination of cracking alone does not guarantee a good corrosion protection.…”

Section: Discussionmentioning

confidence: 99%

Role of Post-Treatment in Improved Corrosion Behavior of Trivalent Chromium Protection (TCP) Coating Deposited on Aluminum Alloy 2024-T3

Ely

Światowska

Seyeux

et al. 2017

J. Electrochem. Soc.

View full text Add to dashboard Cite

The effects of post-treatment applied on Trivalent Chromium Protection (TCP) coatings deposited on aluminum alloy 2024-T3 was studied by electrochemical and surface analytical techniques: X-ray Photoelectron Spectroscopy (XPS) and Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS). The aim of the post-treatment was to improve the corrosion resistance of the TCP coating. To understand the influence of the post-treatment, using a bath containing H 2 O 2 and a lanthanum salt as an inhibitor, our approach was to study the effect of these two components separately. It was found that the improved corrosion protection provided by the post-treated TCP was related to a synergetic effect of the two components. XPS and ToF-SIMS analyses showed that (i) the thickness of the TCP coating is not modified by the post-treatment, (ii) lanthanum is present on the surface and in the bulk of the TCP and (iii) is found in very small amount only on the extreme surface. The total concentration of Cr(VI) (oxide/hydroxide) was estimated to be below 0.1 wt% in the post-treated TCP layer. It was concluded that lanthanum plays a significant role in improving the coating density and homogeneity and has a beneficial effect on the TCP coating cracking as observed by Scanning Electron Aluminum alloys are used for aerospace applications for their low weight and good mechanical properties.1-3 To improve the corrosion properties of aluminum alloys and to provide good paint adhesion, the first layer of coating applied on the aluminum alloy surface used to be a chromate conversion coating (CCC).4-6 However, hexavalent chromium used in the CCC coatings is highly toxic, 4,7 its use is very much restricted in Europe 8 and the United States 9 and will be forbidden by 2024 by the European Community with respect to the Registration, Evaluation, Authorization and Restriction of Chemicals (REACh).8 Therefore, new conversion coatings have been developed, and one of the most promising solutions is the Trivalent Chromium Protection coating called also as the Trivalent Chrome Process (TCP).10-14 TCP conversion coatings are formed by immersion in a solution containing Zr 4+ , Cr 3+ and F − ions, at a pH between 3.8 and 4.0. As it has already been widely discussed, the coating formation mechanism occurs by multiple chemical steps. 10,11,13,[15][16][17] The initial step involves dissolution of the aluminum oxide layer by fluorides. The removal of the oxide layer exposes the metal surface where cathodic reactions take place. Oxygen reduction reaction, and possibly hydrogen discharge, which counterbalance aluminum oxidation, consume protons and causes a pH increase at the interface between the metallic substrate and the solution, as measured by Li et al. 15 The high pH favors the precipitation of ions present in the solution, forming a hydrated layer of zirconium and chromium oxide. The thickness of the TCP layer is usually of the order of 100 nm, depending on the nature of the aluminum alloy, the concentration of the solution and the immersion time.11,12,18 ...

show abstract

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

Cited by 3 publications

References 12 publications

Low-Temperature CO Oxidation over Combustion Made Fe- and Cr-Doped Co₃O₄ Catalysts: Role of Dopant’s Nature toward Achieving Superior Catalytic Activity and Stability

Low-Temperature CO Oxidation over Combustion Made Fe- and Cr-Doped Co₃O₄ Catalysts: Role of Dopant’s Nature toward Achieving Superior Catalytic Activity and Stability

Ultra-Low-Temperature CO Oxidation Activity of Octahedral Site Cobalt Species in Co₃O₄ Based Catalysts: Unravelling the Origin of the Unique Catalytic Property

Role of Post-Treatment in Improved Corrosion Behavior of Trivalent Chromium Protection (TCP) Coating Deposited on Aluminum Alloy 2024-T3

Contact Info

Product

Resources

About

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

Cited by 3 publications

References 12 publications

Low-Temperature CO Oxidation over Combustion Made Fe- and Cr-Doped Co3O4 Catalysts: Role of Dopant’s Nature toward Achieving Superior Catalytic Activity and Stability

Low-Temperature CO Oxidation over Combustion Made Fe- and Cr-Doped Co3O4 Catalysts: Role of Dopant’s Nature toward Achieving Superior Catalytic Activity and Stability

Ultra-Low-Temperature CO Oxidation Activity of Octahedral Site Cobalt Species in Co3O4 Based Catalysts: Unravelling the Origin of the Unique Catalytic Property

Role of Post-Treatment in Improved Corrosion Behavior of Trivalent Chromium Protection (TCP) Coating Deposited on Aluminum Alloy 2024-T3

Contact Info

Product

Resources

About

Low-Temperature CO Oxidation over Combustion Made Fe- and Cr-Doped Co₃O₄ Catalysts: Role of Dopant’s Nature toward Achieving Superior Catalytic Activity and Stability

Low-Temperature CO Oxidation over Combustion Made Fe- and Cr-Doped Co₃O₄ Catalysts: Role of Dopant’s Nature toward Achieving Superior Catalytic Activity and Stability

Ultra-Low-Temperature CO Oxidation Activity of Octahedral Site Cobalt Species in Co₃O₄ Based Catalysts: Unravelling the Origin of the Unique Catalytic Property