Microstructure and corrosion of AA2024

Hughés, A.E.; Parvizi, Reza; Forsyth, Maria

doi:10.1515/corrrev-2014-0039

Cited by 77 publications

(31 citation statements)

References 64 publications

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“…A second group of particles of irregular appearance, whose dimensions range from a few micrometres up to 15 µm, are composed of Al-Cu-Mn-Fe-Si or Al-Cu-Fe-Mn; these are present on the surface as both isolated particles and clusters or clumps of several particles, Figure 2 (see black arrows). The stoichiometry of this second type is more difficult to assign [4,5], but it has been defined as Al-Cu-Mn-Fe-(Si). Conversely, some intermetallic particles have been removed after Pretreatment 2, giving rise to cavities that appear in positions in which there were Al(Cu,Mg) phases, see white arrows in Figure 4a.…”

Section: Surface Morphology and Microstructure Of Uncoated Samplesmentioning

confidence: 99%

“…In fact, the intermetallic particles provide sites on the substrate surface where O 2 reduction can take place, leading to corrosion such as pitting or filiform corrosion. The principal alloy phases in 2024 are Al(Cu,Mg) and Al-Cu-Fe-Mn-Si [1][2][3][4][5][6][7], with different stoichiometry depending on the author consulted. As a consequence, Al-Cu alloys surfaces are often treated in order to reduce the corrosion extension.…”

Section: Introductionmentioning

confidence: 99%

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Influence of Aerospace Standard Surface Pretreatment on the Intermetallic Phases and CeCC of 2024-T3 Al-Cu Alloy

Alba-Galvín

González-Rovira

Bethencourt

et al. 2019

Metals

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A standard three-step surface pretreatment employed in the aerospace sector for Al alloys have been investigated prior to the generation of cerium conversion coatings (CeCC) on aluminium-copper alloy 2024. Two pretreatments were analysed, one without final acid etching (Pretreatment 1) and another with this step (Pretreatment 2). Both pretreatments affect the alloy intermetallic phases, playing a key role in the development of the CeCC, and also in the susceptibility to localised corrosion in NaCl medium. Scanning electron microscopy coupled with energy-dispersive X-ray analysis (SEM-EDX) revealed that after Pretreatment 2, Al(Cu,Mg) phases were partially or totally removed through dealloying with their subsequent copper enrichment. Conversely, none of these intermetallic phases were affected when the final acid step was not employed (Pretreatment 1). Meanwhile, Al-Cu-Fe-Mn-(Si) phases, the other major Al–Cu alloys intermetallics, suffers minor changes through the whole pretreatments chain. The protective efficiency of CeCC was evaluated using electrochemical techniques based on linear polarisation (LP) and electrochemical impedance spectroscopy (EIS). Samples with CeCC deposited after the Pretreatment 1 gave higher polarisation resistance and impedance module than CeCC deposited after Pretreatment 2. SEM-EDX and X-ray photoelectron spectroscopy analysis (XPS) indicate that the main factors explaining the corrosion resistance of the coatings is the existence of Al(Cu,Mg) intermetallics in the surface of the alloy, which promote the deposition of a cerium-based coating rich in Ce4+ compounds. These Al(Cu,Mg) intermetallics were kept in the 2024 alloy when acid etching was not employed (Pretreatment 1).

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Section: Surface Morphology and Microstructure Of Uncoated Samplesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Influence of Aerospace Standard Surface Pretreatment on the Intermetallic Phases and CeCC of 2024-T3 Al-Cu Alloy

Alba-Galvín

González-Rovira

Bethencourt

et al. 2019

Metals

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“…Cu and Mn were detected both in the matrix and constituent IM particles, and Fe only in the constituent particles [59][60][61][62][63][64][65][66][67]. The presence of Cu and Mn in the matrix can be explained by a small but significant solubility of Cu in Al, as well as Cu and Mn being present in a number of IM particles (hardening precipitates (Cu) and dispersoids (Al 20 Mn 3 Cu 2 )), which are much smaller than the resolution of the technique [68]. Elements such as Ga have been reported before when using Rutherford Backscattering spectroscopy (RBS) to examine aluminium alloys [69].…”

Section: Pixe/pigementioning

confidence: 99%

Particle Characterisation and Depletion of Li2CO3 Inhibitor in a Polyurethane Coating

et al. 2017

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The distribution and chemical composition of inorganic components of a corrosion-inhibiting primer based on polyurethane is determined using a range of characterisation techniques. The primer consists of a Li 2 CO 3 inhibitor phase, along with other inorganic phases including TiO 2 , BaSO 4 and Mg-(hydr)oxide. The characterisation techniques included particle induced X-ray and γ-ray emission spectroscopies (PIXE and PIGE, respectively) on a nuclear microprobe, as well as SEM/EDS hyperspectral mapping. Of the techniques used, only PIGE was able to directly map the Li distribution, although the distribution of Li 2 CO 3 particles could be inferred from SEM through using backscatter contrast and EDS. Characterisation was also performed on a primer coating that had undergone leaching in a neutral salt spray test for 500 h. Overall, it was found that Li 2 CO 3 leaching resulted in a uniform depletion zone near the surface, but also much deeper local depletion, which is thought to be due to the dissolution of clusters of Li 2 CO 3 particles that were connected to the external surface/electrolyte interface.

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“…Only pits deeper than 20 m were taken into account, as the effect of shallower pits on the reduction of strength properties can be considered negligible compared to the effect of deeper pits. 28 Since the areas of examination have been randomly selected, the average depth of the 10 deepest pits that have been detected was considered as the representative value concerning the maximum depth of attack. 1 Figure 1 shows the evolution of corrosion damage in representative cross sections of specimens exposed to 3.5% NaCl solution after each period.…”

Section: Metallographic Analysismentioning

confidence: 99%

Effect of environment's aggressiveness on the corrosion damage evolution and mechanical behavior of AA 2024‐T3

Vasco

Chamos

Pantelakis

2017

Fatigue Fract Eng Mat Struct

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The aim of this work is to contribute on establishing correlations between corrosion damage from accelerated laboratory corrosion tests of varying aggressiveness; by accounting for both, the metallographic features of corrosion damage and the mechanical properties of the corroded material. The work is based on the investigation of corrosion damage caused by the exposure of 2024‐T3 aluminum alloy to 3.5% NaCl solution, which is presently considered to properly represent in‐service exposure. Corrosion damage evolution was quantified for periods ranging between 500 and 3000 hours by evaluating pitting density, depth, and diameter. It was compared to available results of corrosion damage of the same alloy subjected to exfoliation corrosion test. Furthermore, the tensile properties of precorroded material in each solution were evaluated. The results allow the formulation of correlation functions between corrosion damage geometrical metallographic features from low‐ to high‐aggressiveness environment exposures. On the other hand, the degradation of tensile properties, and particularly of tensile ductility, is more pronounced in specimens exposed to higher corrosion rate environments, even when damage in both environments leads to equivalent metallographic features. This suggests significant differences in the underlying physical mechanisms of the damage accumulation process when the same material is exposed to different corrosive solutions. This work suggests the need to expand current corrosion damage interpretation, to account not only for geometrical metallographic features but also for mechanical properties of the affected material.

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Microstructure and corrosion of AA2024

Cited by 77 publications

References 64 publications

Influence of Aerospace Standard Surface Pretreatment on the Intermetallic Phases and CeCC of 2024-T3 Al-Cu Alloy

Influence of Aerospace Standard Surface Pretreatment on the Intermetallic Phases and CeCC of 2024-T3 Al-Cu Alloy

Particle Characterisation and Depletion of Li2CO3 Inhibitor in a Polyurethane Coating

Effect of environment's aggressiveness on the corrosion damage evolution and mechanical behavior of AA 2024‐T3

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