Intermetallic Phases in Aluminum Alloys and Their Roles in Localized Corrosion

Zhu, Yakun; Sun, Kai; Frankel, G. S.

doi:10.1149/2.0931811jes

Cited by 156 publications

(124 citation statements)

References 43 publications

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“…The electrochemical behavior of constituent phases may change over time. In a recent study, Zhu et al studied the evolution of corrosion behavior of intermetallic phases in Al alloys over time [43]. At the early stages, the corrosion attack occurred in the form of de-alloying.…”

Section: Resultsmentioning

confidence: 99%

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Relationship between Phase Occurrence, Chemical Composition, and Corrosion Behavior of as-Solidified Al–Pd–Co Alloys

et al. 2019

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The microstructure, phase constitution, and corrosion performance of as-solidified Al70Pd25Co5 and Al74Pd12Co14 alloys (element concentrations in at.%) have been investigated in the present work. The alloys were prepared by arc-melting of Al, Pd, and Co lumps in argon. The Al74Pd12Co14 alloy was composed of structurally complex εn phase, while the Al70Pd25Co5 alloy was composed of εn and δ phases. The corrosion performance was studied by open circuit potential measurements and potentiodynamic polarization in aqueous NaCl solution (3.5 wt.%). Marked open circuit potential oscillations of the Al70Pd25Co5 alloy have been observed, indicating individual breakdown and re-passivation events on the sample surface. A preferential corrosion attack of εn was found, while the binary δ phase (Al3Pd2) remained free of corrosion. A de-alloying of Al from εn and formation of intermittent interpenetrating channel networks occurred in both alloys. The corrosion behavior of εn is discussed in terms of its chemical composition and crystal structure. The corrosion activity of εn could be further exploited in preparation of porous Pd–Co networks with possible catalytic activity.

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Section: Resultsmentioning

confidence: 99%

“…At the early stages, the corrosion attack occurred in the form of de-alloying. However, as the time progressed, the particles became nobler as a result of Al dissolution [43]. This particle ennoblement may accelerate the galvanic dissolution of the surrounding matrix.…”

Section: Resultsmentioning

confidence: 99%

Relationship between Phase Occurrence, Chemical Composition, and Corrosion Behavior of as-Solidified Al–Pd–Co Alloys

et al. 2019

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“…This effect is due to the seawater flow, which accelerates the corrosion process, causing detachment of the destroyed passive layer and the appearance of new "fresh" areas, where the oxygen diffuses and is the oxidising agent in the cathodic corrosion reaction. It is also observed that on both surfaces (Figure 3c and d), some particles remained (named as D and F), and according to EDS (Table 3), they correspond to cathodic rich in Fe [7], reported in the reference sample as α-Al(Fe,Mn,Cu)Si [35]; these intermetallic particles promoted the preferential dissolution of the aluminium matrix [40,41]. Figure 4 compares the φ corr fluctuations of AA6061-T6 specimens exposed for different periods of times (0, 5 and 30 days) under laminar flow conditions (Figure 4a) and without flow (Figure 4b).…”

Section: Surface Analysismentioning

confidence: 81%

Effect of Laminar Flow on the Corrosion Activity of AA6061-T6 in Seawater

Acosta¹,

Véleva²,

Chávez³

et al. 2021

Direct Numerical Simulations - An Introduction and Applications

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The electrochemical behaviour and surface changes on AA6061-T6 alloy exposed to Caribbean seawater from the Cozumel Channel for 30 days under laminar flow (0.1 ms À1) were studied, these contrasting then with stationary conditions. Open circuit potential monitoring and electrochemical current fluctuations, considered as electrochemical noise (EN), were employed as two nondestructive methods. The calculated corrosion current, based on Rn, was one order higher in laminar flow. The fluctuations of current were transformed in the frequency domain. Their power spectral density (PSD) plots were obtained in order to gain information concerning the dynamic of the spontaneous release of energy during the corrosion process. The value of the exponent β in PSD graphs suggested that the localised corrosion on AA6061-T6 surface occurs as a persistent stationary process, which dynamic is controlled by oxygen diffusion. The changes in the morphology and elemental composition of the formed layers revealed that the localised attacks occurred in the vicinity of intermetallic particles rich in Fe and Cu, which act as cathodes.

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“…On amphoteric alloys such as Al, there is concern for the initiation of alkaline corrosion as well (Aballe et al, 2001;Tran et al, 2016). Alkaline corrosion phenomena may be especially severe when constituent particles intersect the alloy surface to act as fast cathodic reaction sites, which will form local alkaline regions that aggravate amphoteric substrate dissolution (Aballe et al, 2001(Aballe et al, , 2003Huang and Frankel, 2007;Zhu et al, 2018;McMahon et al, in review). Thus, the barrier and galvanic properties of the MRP must be properly balanced to optimize performance for specific substrates, with particular attention to reducing the risk for exacerbation of degradation.…”

Section: Optimization and Effectivenessmentioning

confidence: 99%

A Review of Modern Assessment Methods for Metal and Metal-Oxide Based Primers for Substrate Corrosion Protection

et al. 2019

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Pigmented coatings developed for the corrosion protection of engineering alloys have been successful in the field of corrosion control, and thus are ubiquitous in application. Supporting this success are an array of methods to diagnostically assess these systems and measure their state of degradation. These methods assist the development of next generation coatings, in-service evaluation, and post-mortem analysis of performance. This review comprehensively explores these modern assessment methods, used to screen candidate corrosion prevention pigments, assess pigment protection efficiency, quantify overall pigment effectiveness, and/or predict coating service lifetime. Coating service life assessment is conducted based on the class of coating considered, as categorized by (1) chemical inhibition, (2) galvanic protection, (3) high impedance ion barrier, or a combination of these protection mechanisms. Exciting new in-situ and operando methods are growing in use to enable high fidelity measurement of chemical inhibitor release and deposition, such as micro and in-situ Raman spectroscopy and inductively coupled plasma atomic emission spectrometry (ICP-AES), to name a few. In the galvanic protection coating class, service life and the state of coating performance are now being quantified through methods such as galvanostatic pulse and accelerated cycle testing. Galvanic throwing power is assessed by scanning vibrating electrode technique (SVET), multi-electrode array (MEA), and scanning kelvin probe (SKP). The performance of high impedance ion barrier coatings has traditionally been understood through use of electrochemical impedance spectroscopy (EIS) and equivalent circuit modeling, which have been applied to all coating classes. Finite element analysis (FEA) models the combined effects of coating resistance, water layer thickness, and pigment potential on galvanic coupling and/or inhibitor species release as well. The development of effective corrosion prevention pigments and the in-service evaluation of their efficiency/effectiveness demands a broad collection of techniques. These methods now include new advances in thermodynamic modeling via chemical stability diagrams to McMahon et al. Assessment Methods for Metal-Rich Primer Performance assess pigment function in specific conditions, in-situ pH measurement, as well as energy dispersive (EDS) and x-ray photoelectron spectroscopic (XPS) analyses to determine elemental distribution and corrosion product formation. These techniques and more are explored in this review to document the state-of-the-art in the field.

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Intermetallic Phases in Aluminum Alloys and Their Roles in Localized Corrosion

Cited by 156 publications

References 43 publications

Relationship between Phase Occurrence, Chemical Composition, and Corrosion Behavior of as-Solidified Al–Pd–Co Alloys

Relationship between Phase Occurrence, Chemical Composition, and Corrosion Behavior of as-Solidified Al–Pd–Co Alloys

Effect of Laminar Flow on the Corrosion Activity of AA6061-T6 in Seawater

A Review of Modern Assessment Methods for Metal and Metal-Oxide Based Primers for Substrate Corrosion Protection

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