The Role of Intermetallic Particles in Localized Corrosion of an Aluminum Alloy Studied by SKPFM and Integrated AFM/SECM

Davoodi, Ali; Pan, Jinshan; Leygraf, Christofer; Norgren, Stefan

doi:10.1149/1.2883737

Cited by 119 publications

(96 citation statements)

References 45 publications

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“…Therefore, respectively. The arrows indicate that the Mg atom is pulled towards the surface whereas the Si atom is repulsed towards the bulk interior a driving force for localized attack can be expected which indeed is commonly observed in aluminum and magnesium alloys [34,[63][64][65][66].…”

Section: Discussionmentioning

confidence: 84%

“…A technique of special interest in this context is the SKPFM which can provide information about the Volta potential of a locally-probed metallic area in nanometer resolution while the surface is typically in contact with the ambient air [33]. The Volta potential can provide meaningful information about the relative electrochemical nobility of microstructural phases during initial aqueous corrosion of metals or alloys [34,35], yet without a clear understanding of the theory behind.…”

Section: Introductionmentioning

confidence: 99%

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Volta Potential Evolution of Intermetallics in Aluminum Alloy Microstructure Under Thin Aqueous Adlayers: A combined DFT and Experimental Study

et al. 2018

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In this work, first-principle density functional theory (DFT) was used to calculate the work function and Volta potential differences between aluminum alloy matrix and two intermetallic phases (Mg 2 Si and Al 2 Cu) with varying surface terminations as a function of adhering monolayers (ML) of water. The calculated data were compared with experimental local Volta potential data obtained by the scanning Kelvin probe force microscopy (SKPFM) on a commercial aluminum alloy AA6063-T5 in atmospheric environments with varying relative humidity (RH). The calculations suggest that the surface termination has a major effect on the magnitude and polarity of the Volta potential of both intermetallic phases (IMP's). The Volta potential difference between the IMP's and the aluminum matrix decreases when the surface is gradually covered by water molecules, and may further change as a function of adhering ML's of water. This can lead to nobility inversions of the IMP's relative to the aluminum matrix. The measured Volta potential difference between both IMP's and their neighboring matrix is dependent on RH. Natural oxidation in ambient indoor air for 2 months led to a nobility inversion of the IMP's with respect to the aluminum matrix, with the intermetallics showing anodic nature already in dry condition. The anodic nature of Al 2 Cu remained with the introduction of RH, whereas Mg 2 Si became cathodic at high RH, presumably due to de-alloying of Mg and oxide dissolution. The DFT calculations predicted an anodic character of both IMP's in reference to the oxidized aluminum matrix, being in good agreement with the SKPFM data. The DFT and SKPFM data were discussed in light of understanding localized corrosion of aluminum alloys under conditions akin to atmospheric exposure.

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Section: Discussionmentioning

confidence: 84%

Section: Introductionmentioning

confidence: 99%

Volta Potential Evolution of Intermetallics in Aluminum Alloy Microstructure Under Thin Aqueous Adlayers: A combined DFT and Experimental Study

et al. 2018

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“…Examples include; spontaneous passivity of Mg 2 Si at alkaline pH and the increase in the ability of Fe-containing intermetallics to sustain ORR as either pH or [Cl − ] increase, to name but a couple of important factors. 7,9 Similarly, such richness is not predicted by methods such as SKPFM, which has been previously used to predict localized corrosion on the basis of Volta potentials measured in air; [14][15][16] highlighting that kinetic information, in the electrolyte and conditions of interest cannot be simply substituted.The role of temperature on corrosion of bulk AA7075-T651 was reported by Cavanaugh, 12,17 whereby it was revealed temperature played a more significant role than alloy orientation (relative to the rolling direction) or chloride concentration. The only environmental variable more significant than temperature was the realization of extremes * Electrochemical Society Active Member.…”

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confidence: 99%

Electrochemical Characterization of Intermetallic Phases Common to Aluminum Alloys as a Function of Solution Temperature

Cavanaugh

Birbilis

et al. 2014

J. Electrochem. Soc.

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A practically important scenario in the corrosion of aluminum (Al) alloys is the variation in damage characteristics, i.e. mode, rate and morphology, as function of environmental temperature. In order to address this problem from a mechanistic point of view, this paper presents results for corrosion potentials, pitting potentials and electrochemical characteristics for intermetallic particles commonly present in high strength aluminum alloys, for tests conducted in 0.1M NaCl of varying temperature. Tests were conducted between 0 and 60 • C via the use of a micro-capillary electrochemical cell. The intermetallics investigated were Mg 2 Si, MgZn 2 , Al 7 Cu 2 Fe, Al 2 Cu, Al 2 CuMg and Al 3 Fe. Analysis of the results reveals that the electrochemical behavior of such compounds is heavily dependent on temperature, with ramifications for localized corrosion (and protection) In the most general sense, corrosion represents the adverse intersection between a material and the environment; while in the case of aluminum (Al) alloys, their prescription is widespread and covers many environmental exposure conditions. For a given material, the environment is responsible for the type and extent of corrosion that may result; warranting an investigation of the electrochemical characteristics as function of environment. [1][2][3][4][5][6] In an attempt to unambiguously characterize the mechanistic aspects of localized corrosion of heterogeneously structured high-strength Al-alloys, we have presented the electrochemical characteristics for a number of intermetallic particles and phases common to a large range of such alloys, [7][8][9][10] paying particular attention to the effect of chloride concentration 9 and the effect of solution pH.7 This approach has also recently been followed for investigation of the second phases that occur in magnesium alloys. 11It has been shown that both [Cl − ] and pH have a significant effect upon the corrosion morphology and rate of bulk Al-alloys, as demonstrated for AA7075-T651. 12 Of key relevance to the work herein, it was shown that the resultant alloy corrosion was able to be reconciled in terms of both morphology and rate, from knowledge of the individual electrochemical characteristics of the alloy constituents.13 Furthermore, it is of importance to note that the associated electrochemical kinetics upon alloy constituents is not trivial, in that kinetics may not be accurately predicted based upon composition or knowledge of corrosion potentials alone. However, polarization testing was able to reveal significant quantitative insights allowing a leap in understanding the origins of localized corrosion (and in some cases the absence of localized corrosion). Examples include; spontaneous passivity of Mg 2 Si at alkaline pH and the increase in the ability of Fe-containing intermetallics to sustain ORR as either pH or [Cl − ] increase, to name but a couple of important factors. 7,9 Similarly, such richness is not predicted by methods such as SKPFM, which has been previously used to predict loca...

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“…The Al 3+ ions being released into the solution reduced I 3 -to I -which was detected at the probe. The initiation of pitting corrosion [214] as well as the influence of intermetallic particles on the corrosion behavior of the Al alloy EN AW-3003 [244][245][246] and the development of active corrosion sites [247] was followed. A comparison between the corrosion properties of EN AW-3003 and a recently developed Al-Mn-Si-Zr alloy has shown a significantly higher number of corroding sites and pits on EN AW-3003 [247].…”

Section: +mentioning

confidence: 99%

Investigation of Localized Catalytic and Electrocatalytic Processes and Corrosion Reactions with Scanning Electrochemical Microscopy (SECM)

Pust¹,

Maier²,

Wittstock³

2008

Zeitschrift Für Physikalische Chemie

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Scanning Electrochemical Microscopy (SECM) . Catalytic Electrodes .Electrochemical Energy Conversion . Fuel Cells . Oxygen Reduction Reaction . CorrosionScanning electrochemical microscopy (SECM) has developed into a very versatile tool for the investigation of solid-liquid, liquid-liquid and liquid-gas interfaces. The arrangement of an ultramicroelectrode (UME) in close proximity to the interface under study allows the application of a large variety of different experimental schemes. The most important have been named feedback mode, generation-collection mode, redox competition mode and direct mode. Quantitative descriptions are available for the UME signal, depending on different sample properties and experimental variables. Therefore, SECM has been established as an indispensible tool in many areas of fundamental electrochemical research. Currently, it also spreads as an important new method to solve more applied problems, in which inhomogeneous current distributions are typically observed on different length scales. Prominent examples include devices for electrochemical energy conversion such as fuel cells and batteries as well as localized corrosion phenomena. However, the direct local investigation of such systems is often impossible. Instead, suitable reaction schemes, sample environments, model samples and even new operation modes have to be introduced in order to obtain results that are relevant to the practical application. This review outlines and compares the theoretical basis of the different SECM working modes and reviews the application in the area of electrochemical energy conversion and localized

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The Role of Intermetallic Particles in Localized Corrosion of an Aluminum Alloy Studied by SKPFM and Integrated AFM/SECM

Cited by 119 publications

References 45 publications

Volta Potential Evolution of Intermetallics in Aluminum Alloy Microstructure Under Thin Aqueous Adlayers: A combined DFT and Experimental Study

Volta Potential Evolution of Intermetallics in Aluminum Alloy Microstructure Under Thin Aqueous Adlayers: A combined DFT and Experimental Study

Electrochemical Characterization of Intermetallic Phases Common to Aluminum Alloys as a Function of Solution Temperature

Investigation of Localized Catalytic and Electrocatalytic Processes and Corrosion Reactions with Scanning Electrochemical Microscopy (SECM)

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