Influence of pre-treatment on the surface composition of Al–Zn alloys

Gentile, M.; Королева, Е. В.; Skeldon, P.; Thompson, G.E.; Bailey, Paul; Noakes, T.C.Q.

doi:10.1016/j.corsci.2009.10.023

Cited by 4 publications

(4 citation statements)

References 20 publications

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“…This observation complicates the analysis of the true near-surface Zn after etching. Moreover, enrichment of Zn on the more active grains by dealloying is an expected result, 7 assuming that the aluminum matrix is more active in alkaline solution than the Zn component of the alloy. If Zn enrichment were a result of a dissolution-redeposition mechanism, then Zn enrichment of the surface of the more noble grains would be expected.…”

Section: C426mentioning

confidence: 99%

Preferential Grain Etching of AlMgSi(Zn) Model Alloys

Holme

Ljones

Bakken

et al. 2010

J. Electrochem. Soc.

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Preferential grain etching is a problem occurring on aluminum products during alkaline etching prior to anodizing, especially if the etching bath contains small amounts of dissolved Zn. The visually uneven, “grainy” surface is caused by different etch rates for different grains, giving a terracelike surface topography. Polished samples of an AlMgSi alloy with different amounts of Zn were etched in NaOH solution. Grain orientations in selected areas were determined by electron backscatter diffraction. The low-Zn samples did not show preferential grain etching. On the higher-Zn alloys, grains with surface planes close to {111} were found to etch at a higher rate than those with other orientations. Secondary ion mass spectrometry depth profiling and imaging, combined with white light interferometry analysis, showed a clear correlation between the deep lying grains and a surface enriched in Zn, suggesting that Zn enrichment by alkaline etching occurred by selective dissolution of aluminum rather than a dissolution–redeposition mechanism. Zn-enriched grains become more active than the other grains as a result of a decrease in the rate of the water reduction reaction.

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Section: C426mentioning

confidence: 99%

Preferential Grain Etching of AlMgSi(Zn) Model Alloys

Holme

Ljones

Bakken

et al. 2010

J. Electrochem. Soc.

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“…The surface enrichment of Cu, Fe, and Mn on the metal side of the metal/oxide interface and the growing oxide precursor layer with etching time lets us reason that the transport of these alloy elements into the solution must occur through the oxide precursor layer. Also other studies found enrichment of Zn, 79,80 and Cu 32,81 on the metal side of the metal/oxide interface. Furthermore, the presence of an enrichment of Cu, Mn, Cr and Fe on the oxide side of the metal/ oxide interface can be because of either the redeposition of these elements from the etching solution, or their transport through the oxide precursor layer.…”

Section: Discussion: Surface Enrichment Of Alloy Elements and Effect ...mentioning

confidence: 71%

Recycled Aluminium Alloys and their Models: Role and Behaviour of Alloying Elements during Alkaline Etching

Mysliu¹,

Storli²,

Kjørsvik³

et al. 2023

J. Electrochem. Soc.

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Alkaline etching is a common pretreatment for aluminium surfaces. Etching behaviour was compared between an alloy based on post-consumer scrap (PCS) and several model alloys of rolled AA3005 and extruded AA6060 with systematically varied amounts of Mn, Cu, and Ni. Analysis of concentrations of alloy elements in the etching solution by inductively coupled plasma mass spectrometry (ICP-MS) shows that significant fractions of the investigated elements Cu, Fe, Mg, Mn, Ni, and Zn dissolve. Surface analysis of samples in different stages of the etching process show (i) an increase in oxide layer thickness with etching time, (ii) an enrichment of important alloy elements and impurities (Cr, Cu, Fe, Mg, Mn, Si) near the metal/oxide interface, and (iii) the deposition of Mg, Fe, Si-containing aluminium hydroxide on the surface. A comparison with open circuit potential measurements and time-resolved electrochemical polarisation resistance measurements enables a detailed analysis of the etching mechanism. The aluminium dissolution rate during etching is limited by the transport of species through the oxide precursor layer, making it potential-independent. Differences in etching rates between different alloy classes, evidenced by mass loss measurements, are related to differences in the cathodic or anodic reaction mechanisms (hydrogen evolution or metal dissolution) during etching.

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“…However, a few small pits the size of a few micrometers were observed on the brass-RCE surface. This is possibly the result of the enrichment of the Zn element beneath the oxide/hydroxide films on the brass surface [19]. Figure 5a-d shows the surface morphologies of the brass-RCEs potentiostatically etched at the end of their limiting-current plateau at different rotational speeds.…”

Section: Potentiostatic Polishing On the Limiting-current Plateaumentioning

confidence: 99%

“…Based on the latter mechanism, the mass transport is controlled by the transportation of complex ions from electrode into the anode surface. In the acceptor mechanism, the mass transport is limited by the acceptor species, such as water molecules or anions [18,19], adjacent to the anode in which the concentration of acceptor species is exhausted through reaction with the metallic cations.…”

Section: Introductionmentioning

confidence: 99%

Electropolishing Behaviour of 73 Brass in a 70 vol % H3PO4 Solution by Using a Rotating Cylinder Electrode (RCE)

Huang

Chen

Sun

2017

Metals

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Abstract:The electropolishing behaviour of 73 brass was studied by means of a rotating cylinder electrode (RCE) in a 70 vol % H 3 PO 4 solution at 27 • C. Owing to the formation of a blue Cu 2+ -rich layer on the brass-RCE, an obvious transition peak was detected from kinetic-to diffusion-controlled dissolution in the anodic polarisation curve. Electropolishing was conducted at the potentials located at the transition peak, the start, the middle, and the end positions in the limiting-current plateau corresponding to the anodic polarisation curve of the brass-RCE. A well-polished surface can be obtained after potentiostatic electropolishing at the middle position in the limiting-current plateau. During potentiostatic etching in the limiting-current plateau, a blue Cu 2+ -rich layer was formed on the brass-RCE, reducing its anodic dissolution rate and obtaining a levelled and brightened brass-RCE. Moreover, a rod climbing phenomenon of the blue Cu 2+ -rich layer was observed on the rotating brass-RCE. This enhances the coverage of the Cu 2+ -rich layer on the brass-RCE and improves its electropolishing effect obviously.

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Influence of pre-treatment on the surface composition of Al–Zn alloys

Cited by 4 publications

References 20 publications

Preferential Grain Etching of AlMgSi(Zn) Model Alloys

Preferential Grain Etching of AlMgSi(Zn) Model Alloys

Recycled Aluminium Alloys and their Models: Role and Behaviour of Alloying Elements during Alkaline Etching

Electropolishing Behaviour of 73 Brass in a 70 vol % H3PO4 Solution by Using a Rotating Cylinder Electrode (RCE)

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