The anodic and cathodic dissolution of Al and Al–Cu–Mg alloy

The cathodic dissolution of aluminium in neutral medium was studied by electrochemical methods. It is shown that oxygen reduction at the surface of the metal is kinetically controlled and that the diffusion regime is never reached due to the poor conductivity of the oxide film and consequently a high potential drop across the layer. Nevertheless, at E < -1.4 V/MSE, the rate of hydroxyl production during oxygen reduction is high enough to raise the interfacial pH

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“…A more accurate value for C ox can be obtained from C HF and C dl values according to equation (16):…”

Section: Eis Modelmentioning

confidence: 99%

“…Ogle et al [16,17] used atomic emission spectroelectrochemistry (AESEC) to follow the Al dissolution rate during the cathodic polarization of an aluminium electrode. They demonstrated that cathodically generated hydroxide is responsible for chemical dissolution of the oxide/hydroxide layer formed at the open-circuit potential.…”

Section: Introductionmentioning

confidence: 99%

New insights into the cathodic dissolution of aluminium using electrochemical methods

Tran

Tribollet

Sutter

2016

Electrochimica Acta

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“…Indeed, sharp spikes are revealed, representing the release of Cu rich particles that are transported to the plasma. 44,45 In previous work, we have demonstrated that solid particles entering the plasma will give rise to a peak of <10 ms in duration.…”

Section: Resultsmentioning

confidence: 99%

“…It is noted that ν Cu in NaOH may be theoretically underestimated if undetected Cu rich particles are too large to be measured efficiently by ICP-OES. 44,45 To determine this, the quantities of Al and Cu released during the NaOH exposure were measured by collecting the electrolyte downstream from the plasma (Fig. 1).…”

Section: Resultsmentioning

confidence: 99%

“…The result shows that Cu dissolution is remarkably enhanced by the surface pretreatment sequence. For the untreated surface, Cu dissolution is almost exclusively in the form of particles with very little background Cu dissolution suggesting a non-faradaic Cu release, 14,45 where Cu nanoparticulates physically detach from the surface during the dissolution of Al and Mg. For the treated surface however, a steady signal of Cu dissolution increases along with j e and j Al . Nevertheless, Cu dissolution is well below that expected for a stoichiometric dissolution.…”

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confidence: 99%

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In-Situ Monitoring of Alloy Dissolution and Residual Film Formation during the Pretreatment of Al-Alloy AA2024-T3

Gharbi

Birbilis

Ogle

2016

J. Electrochem. Soc.

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The dissolution of intermetallic phases in AA 2024-T3 aluminum alloy sheet was investigated during a coating pretreatment sequence. The atomic emission spectroelectrochemistry (AESEC) technique was used to quantitatively measure the dissolution rates of individual alloying elements during a complete pretreatment sequence. The results demonstrate the significant selective dissolution of Al in 1.25 M NaOH, leading to the enrichment of alloying elements such as Cu. Subsequent 2.8 M HNO 3 treatment contributes toward dissolving the excess residual layer and passivates the alloy matrix, however the presence of a residual Cu layer at the alloy surface was evidenced. The real-time alloy dissolution profiles are presented herein, and discussed in the context of the surface morphology via microscopy. The surface treatment of aluminum (Al) alloys is required prior to the application of corrosion protective coatings.1 Protective coatings are essential in order to allow microstructurally complex alloys, which are nominally prone to localized corrosion, 2-7 to be used in service; particularly in aerospace applications.8 Coatings for Al-alloys are nominally multilayered coating 'systems', with the first coating being a chemical conversion coating. The surface treatment prior to this chemical conversion coating is as important as the coating itself, since it determines the efficacy of any conversion coating.1,9 Such surface treatment, often termed pre-treatment, generally involves alkaline etching and acid pickling. Sodium hydroxide (NaOH) is often used to remove any organic residue and also to remove several micrometers of the alloy surface.10 This is followed by acid pickling, usually performed in nitric acid (HNO 3 ) to remove any residue, products, films, or particles remnant from -or caused by -the prior alkaline step. The purpose of surface pretreatment is to provide a chemically homogeneous surface chemistry prior to subsequent coating processes. The chemical heterogeneity of the Al-alloy surfaces is due to the many alloying elements present, such as copper (Cu), magnesium (Mg), iron (Fe) and manganese (Mn). Cu improves the mechanical properties of AA 2024-T3 11 however decreases corrosion resistance due to stimulating various phases which serve as local electrochemical entities, in addition to raising the alloy potential to above the pitting potential of the matrix phase 7,[12][13][14][15][16] . This element is considered to be a major contributor to the localized corrosion of Al 2,17,18 and its elimination is one of primary goals of aluminum alloy surface pretreatment.Knowledge of the elementary dissolution kinetics during the pretreatment sequence would be very useful for the development of surface treatment formulations, however, this information is often very difficult to obtain. In situ monitoring of the corrosion reactions during surface treatment is difficult as the corrosion reactions occur within a relatively short time with large reaction rates and may involve extensive precipitation of dissolution products a...

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Deposition of Environmentally Compliant Cerium‐Containing Coatings and Primers on Copper‐Containing Aluminium Aircraft Alloys

Kozhukharov

2016

Biobased and Environmental Benign Coatings

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The anodic and cathodic dissolution of Al and Al–Cu–Mg alloy

Cited by 86 publications

References 28 publications

New insights into the cathodic dissolution of aluminium using electrochemical methods

New insights into the cathodic dissolution of aluminium using electrochemical methods

In-Situ Monitoring of Alloy Dissolution and Residual Film Formation during the Pretreatment of Al-Alloy AA2024-T3

Deposition of Environmentally Compliant Cerium‐Containing Coatings and Primers on Copper‐Containing Aluminium Aircraft Alloys

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