Surface charge at the oxide-covered aluminium-electrolyte interface

Bolanča, Zdenka; Korelić, O.; Lovreček, B.

doi:10.1016/0376-4583(84)90095-5

Cited by 6 publications

(3 citation statements)

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“…Therefore, we conclude that chloride mainly migrates into the oxide layer (is then less mobile) while sulfate mainly adsorbs at the oxide/solution interface. More quantitatively, , using the mobility argument, we may conclude that up to 70% of surface chloride and only 25% of surface sulfate are incorporated in the oxide layer.…”

Section: Discussionmentioning

confidence: 95%

Sorption of Sulfate and Chloride Anions on a Well-Characterized Al 2024 Electrode

et al. 1998

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We studied sorption processes, adsorption and incorporation, of sulfate and chloride anions on the surface of well-characterized aluminum 2024 alloy using electrochemical, radiochemical, and ultrahigh-vacuum spectroscopic techniques. The measurements were carried out at an open-circuit potential and in the electrode potential range on the negative side of the open-circuit potential (cathodic polarization conditions), at various pH values. The focus was on sorption reversibility as well as on the relationship between anion's surface concentration and the electrode potential. We have found that sorption of sulfate anion is controlled by pH, surface charge, and the stability of aluminum oxide films. We have also found that adsorption of chloride is weaker than sulfate and is more irreversible since chloride incorporation occurs more readily than sulfate. The change in the alloy surface composition and morphology induced by the electrochemical treatment and anion adsorption was monitored by scanning Auger microscopy and energy-dispersive X-ray spectroscopy. The characterization exhibits copper-rich intrusions and extrusions that may act as either local cathodes or anodes in the overall alloy dissolution process. The distribution and evolution of such Cu-rich inclusions under studied experimental conditions were monitored and are reported. The dissolution of aluminum from the alloy affects both sulfate and chloride adsorption/incorporation processes. While sulfate and chloride adsorption have no effect on cathodic current measured in the studied electrode potential range, the high anion surface concentration may have a detrimental effect on the alloy stability, particularly when the beneficial influence of the cathodic polarization (protection) ends.

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Section: Discussionmentioning

confidence: 95%

Sorption of Sulfate and Chloride Anions on a Well-Characterized Al 2024 Electrode

et al. 1998

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“…So far, changes in the oxide chemistry on aluminum have been explained in terms of changes in the acid-base properties [7][8] , the surface charge [9][10][11] and the hydroxyl fraction [12][13] . It is interesting to note that although the incorporation of anions during anodizing in sulfuric and phosphoric acids has been extensively reported (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…So far, changes in the oxide chemistry on aluminum have been explained in terms of changes in the acid–base properties, , the surface charge, − and the hydroxyl fraction. , It is interesting to note that although the incorporation of anions during anodizing in sulfuric and phosphoric acids has been extensively reported (e.g., refs − ), studies including these type of pretreatments did not explicitly account for their presence. ,, Because it is mostly the outer region of the oxide, the part that comes into contact with the organic resin, that is contaminated by these anions, , their consideration seems vital to understand how electrolyte variations will affect interfacial bonding with organic resins on a molecular and atomic level.…”

Section: Introductionmentioning

confidence: 99%

XPS Analysis of the Surface Chemistry and Interfacial Bonding of Barrier-Type Cr(VI)-Free Anodic Oxides

Abrahami

Hauffman

Kok³

et al. 2015

J. Phys. Chem. C

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In the transition to environmental friendly pretreatment of aerospace aluminum alloys, chromic acid anodizing (CAA) is being replaced by sulfuric acid (SAA), phosphoric acid (PAA) or phosphoric-sulfuric acid (PSA) anodizing. While generally the main concern is controlling the film morphology, such as the pore diameter, oxide-, and barrier layer thickness, little is known on how the anodic oxide chemistry affects the interactions at the interface upon adhesive bonding. To study the link between surface chemistry and interfacial bonding, featureless oxides were prepared by stopping the anodizing during the formation of the barrier layer. A model was developed to quantify the relative amounts of OH -, PO 4 3-and SO 4 2-by curve-fitting the XPS data.Calculations showed that almost 40% of the surface species in PAA oxide are phosphates (PO 4 3-), while about 15% are sulfates (SO 4 2 ) in SAA. When both anions were present in the electrolyte, phosphate incorporation was inhibited. Studies of the interaction between this set of Cr(VI)-free oxides and diethylenetriamine (DETA) -an amine curing-agent for epoxy resin, showed that all oxides interact with the nitrogen of DETA. However, larger ratios of Lewis-like acid-base bonding between the amine electron pair and the acidic hydroxyl on phosphate surface sites were observed.

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