Cathodic Behavior of Impure Aluminum in Aqueous Media

̧ancioǦlu, Kemal Nis; Davanger, Knut Yngve; Strandmyr, Oystein; Holtan, Hans

doi:10.1149/1.2127675

Cited by 38 publications

(15 citation statements)

References 8 publications

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“…Nisanciog 4lu also observed ditches at E < Ϫ0.9 V (vs. SCE) for Al-1050 alloy and suggested local alkalization created in that case by H ϩ cathodic reaction on the intermetallics was responsible for the formation of ditches. 1 Shape evolution during local dissolution around the intermetallics was investigated by obtaining ex situ AFM images. Figure 2 shows large-area AFM scans of different locations after various periods of exposure between 0 and 230 min.…”

Section: Resultsmentioning

confidence: 99%

“…It is well known that the corrosion behavior of aluminum alloys is significantly affected by the presence of Fe-rich intermetallic particles which form inclusions in the host metal. [1][2][3][4] Such inclusions are the sites where corrosion pits form, although the chemical aspects of the process by which pit initiation occurs are not entirely clear. The present work investigated electrochemical behavior of Al 3 Fe inclusions and their role in creating locally aggressive chemical environment which influences local metal dissolution.…”

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confidence: 99%

“…The formation of the layer was proposed to cause the shift of the corrosion potential to the more positive and stable value. Nisanciog 4lu et al 1 also investigated the cathodic behavior of Al 3 Fe inclusions and found that a cathodic potential of Ϫ1.2 V SCE was necessary to remove these particles and thus avoid pitting. These authors attributed pitting near inclusions to local alkalization at the Al 3 Fe cathodic sites and also to the limited buffer capacity of the solution against large pH excursions.…”

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confidence: 99%

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Influence of Fe‐Rich Intermetallic Inclusions on Pit Initiation on Aluminum Alloys in Aerated NaCl

Park

Paik

Huang

et al. 1999

J. Electrochem. Soc.

197

126

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The role that Al3normalFe intermetallic inclusions play during initiation of pitting corrosion on aluminum alloys was investigated in 0.6 M NaCl. In aerated solutions microscopic observations showed the growth of cavities in the host metal adjacent to inclusions. The rest potential of synthetic Al3normalFe was measured in aerated and deaerated NaCl solutions over a range of bulk pH values between 2 and 12 and was found to act as a cathode. In aerated solutions rotating disk electrode experiments on synthetic Al3normalFe electrodes verified that the cathodic reaction corresponded to the reduction of dissolved oxygen. With scanning pH microelectrodes, measurements were carried out near synthetic Al3normalFe electrodes which were coupled in a galvanic cell with Al-6061 in NaCl solution. In addition, the pH measured over Al-6061 at a distance of 25–30 μm from the surface was observed to fluctuate between pH 4 and 8.5 for the first 2 h of immersion in NaCl solutions. Atomic force microscopy images of Al-6061 immersed in buffered aerated 0.6 M NaCl solution (pH 5.5) did not show any evidence of dissolution of the Al around intermetallics. These measurements support the view that Al3normalFe particles in Al-6061 serve as local cathodes, that a high pH develops around the intermetallic particles and creates cavities in the host metal, and that interactions among a cluster of intermetallic particles causes a large number of slowly dissolving alkaline cavities to evolve into a small number of rapidly dissolving acidic pits. © 1999 The Electrochemical Society. All rights reserved.

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Section: Resultsmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Influence of Fe‐Rich Intermetallic Inclusions on Pit Initiation on Aluminum Alloys in Aerated NaCl

Park

Paik

Huang

et al. 1999

J. Electrochem. Soc.

197

126

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“…1) that at potentials of -0?9 and -1 V(SCE), the current densities are at their maximum values initially and after a short time become constant. Nisancioglu and his coworkers, 8,12,21 believe that in such a condition, cathodic reactions are intense initially, so that intermetallic particles are detached from the pits; the bottoms of the pits are passivated soon after the detachment of particles.…”

Section: Discussionmentioning

confidence: 99%

Effect of cathodic polarisation on pitting corrosion of AA5083-H321 aluminium–magnesium alloy in stagnant 3·5% NaCl solution

Jafarzadeh¹,

Shahrabi²,

Hosseini³

2009

Corrosion Engineering, Science and Technology

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Aluminium-magnesium alloy AA5083-H321 is a suitable material for construction of high speed boats, submarines, desalination systems etc. Cathodic protection is the proposed method for protection against its pitting corrosion. In this research, cathodic polarisation of this alloy has been studied in stationary 3?5% sodium chloride solution at 20?9, 21, 21?1 and 21?2 V(SCE). The electrochemical behaviour of the surface was investigated with EIS and DC methods. Morphological changes on the surface and cross-section of the samples were studied using scanning electron microscope (SEM) and EDAX analyser. The results showed that the fraction of the surface covered by pits, increases with applying more negative potentials. More alkaline electrolyte inside the pits on the surface tends to show non-ideal behaviour for capacitance inside the oxide layer and for oxide layer/solution interface. This behaviour is intensified with increasing of negative potential by deepening of pits during cathodic polarisation of the alloy. The final result is that cathodic protection of this alloy immersed in stationary conditions is impossible.

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“…show the caustic etched and desmutted surface of the AA6111-T4PNA alloy in the as-received condition and following aging treatments at various temperatures. In general, all etched surfaces exhibited a scalloped topography, which is the characteristic of an aluminium surface uniformly etched in alkaline solutions[15]. The significant scalloping of the etched surfaces is an indication to the considerable amounts of the α-intermetallic particles, which have been trenched and lost to the solution during the etching process, leaving cavities at their original locations.…”

mentioning

confidence: 96%

The Influence of Heat Treatment on the Caustic Etching Behaviour of the Automotive AA6111 Alloy

Abouarkoub¹,

Thompson²,

Zhou³

et al. 2016

JMMCE

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The caustic etching behaviour of the automotive AA6111 alloy with different aging conditions that simulate the various levels of heat input within the heat affected zone during the welding heating cycles has been investigated. The alloy dissolution rate was found to substantially increase with the pre-aging temperature, which enhances precipitation of the cathodic Q-phase and results in depletion of the alloy solid solution in magnesium and silicon. On the other hand, enhancing the kinetics of precipitation at high temperatures induces a more uniform distribution the Q-phase precipitates, which minimizes the potential difference between the interiors and boundaries of the adjacent grains. This was observed to reduce the severity of the surface topography developed by subsequent caustic etching surface pre-treatment.

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Cathodic Behavior of Impure Aluminum in Aqueous Media

Abstract: not Available.

Cited by 38 publications

References 8 publications

Influence of Fe‐Rich Intermetallic Inclusions on Pit Initiation on Aluminum Alloys in Aerated NaCl

Influence of Fe‐Rich Intermetallic Inclusions on Pit Initiation on Aluminum Alloys in Aerated NaCl

Effect of cathodic polarisation on pitting corrosion of AA5083-H321 aluminium–magnesium alloy in stagnant 3·5% NaCl solution

The Influence of Heat Treatment on the Caustic Etching Behaviour of the Automotive AA6111 Alloy

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