Using EIS to analyse samples of Al–Mg alloy AA5083 treated by thermal activation in cerium salt baths

Bethencourt, M.; Botana, Francisco; Cano, M.J.; Marcos, M.; Sánchez-Amaya, J.M.; González-Rovira, L.

doi:10.1016/j.corsci.2007.12.009

Cited by 42 publications

(18 citation statements)

References 19 publications

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“…Both events bring about a reduction in the activity of the system. In accordance with the previous observations, it is proposed in [30,31] to use the value of the slope of the passivity section of the LP curves, on a linear scale, as a measure of the resistance of the mixed layer R cp (Eq. [2]).…”

Section: Resultsmentioning

confidence: 74%

“…[30] In this work, the authors showed the beneficial effect of the temperature in cerium baths with the formation of a layer of oxide of sufficient thickness and compacity. In these treatments, not only the cathodic sites of the alloy are blocked and a layer of aluminum oxide/hydroxide is formed on the metal matrix, but also the dielectric properties of this layer are modified; this makes the layer act as a better insulating barrier.…”

Section: Resultsmentioning

confidence: 96%

“…For this reason, to perform the electrochemical characterization of the mixed layer, it is necessary only to analyze the zone of the spectrum between 10 kHz and 1 Hz. [26,30] Table III presents the values associated with the layer, after the evaluation of the EIS spectra. What is notable in this table is that, as indicated, the samples protected present a higher R c in the Nyquist diagrams for all the cases; this is indicative of the greater degree of protection.…”

Section: Resultsmentioning

confidence: 99%

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Protection by Thermal and Chemical Activation with Cerium Salts of the Alloy AA2017 in Aqueous Solutions of NaCl

Bethencourt

Botana

Cano

et al. 2011

Metall Mater Trans A

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A wide variety of anticorrosive treatments for aluminum alloys that can be employed as ''green'' alternatives to those based on Cr(VI) are currently under development. This article reports a study of the morphological and anticorrosive characteristics of surface layers formed on the AlCu alloy AA2017 by immersion treatment in baths of cerium salt, accelerated by increased temperature and the employment of hydrogen peroxide. Scanning electron microscopy (SEM)/ X-ray energy dispersive spectroscopy (XEDS) studies of the samples treated have demonstrated the existence of a heterogeneous layer formed by a film of aluminum oxide/hydroxide on the matrix, and a series of dispersed islands of cerium over the cathodic intermetallics. The protective efficacy has been evaluated using electrochemical techniques, linear polarizations (LP) and electrochemical impedance spectroscopy (EIS), and salt spray tests. The results obtained indicate that the layer provided good resistance to corrosion in media with chlorides, and the method gives a considerable reduction of the time required for the immersion treatments.

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Section: Resultsmentioning

confidence: 74%

Section: Resultsmentioning

confidence: 96%

Section: Resultsmentioning

confidence: 99%

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Protection by Thermal and Chemical Activation with Cerium Salts of the Alloy AA2017 in Aqueous Solutions of NaCl

Bethencourt

Botana

Cano

et al. 2011

Metall Mater Trans A

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“…Other bodies of work in this area include the work of Mansfeld and co-workers, 154,[167][168][169][170][171][172] as well as those of Botana, Abelle, Bethencourt and co-workers 68,102,173,174 who developed boehmite-like coatings on the matrix of alloys using conversion coating solutions containing cerium nitrate. It is diffi cult to draw general conclusions from the literature in this area as a variety of pretreatments are used.…”

Section: Boehmite Formation In Solutions Containing Rare Earthsmentioning

confidence: 99%

Coatings for corrosion prevention based on rare earths

Hughes

Harvey

Birbilis

et al. 2014

Rare Earth-Based Corrosion Inhibitors

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“…1,2 Investigations into improving the corrosion properties of AA5xxx have focused on suppressing precipitation by alloying addition or changing the microstructure, [3][4][5][6] or on application of corrosion inhibitors. [7][8][9][10][11][12][13][14][15] Aballe et al studied the corrosion mechanism of the Al-Mg alloys in 3.5 wt% NaCl and concluded that localized corrosion results from the alkalinization around the cathodic sites, such as Fe-rich intermetallic particles in the metal matrix. 7 Based upon this idea, inhibiting the cathodic reaction is expected to be a promising method to mitigate the corrosion on Al-Mg alloys.…”

mentioning

confidence: 99%

Corrosion Inhibition of Sensitized and Solutionized AA5083

Seong

Frankel

Sridhar³

2015

J. Electrochem. Soc.

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Al-Mg alloys can precipitate β phase, Mg 2 Al 3 , along grain boundaries during long-term exposure to moderate temperatures, resulting in susceptibility to intergranular corrosion. It is of interest to investigate the corrosion inhibition of this alloy in this sensitized condition. Furthermore, recent work has shown that the presence of an altered surface layer (ASL) affects the corrosion behavior of polished AA5083, making it difficult to determine the effectiveness of corrosion inhibitors. The combined effects of the presence of the ASL and inhibitors are not well understood. In this work, the effects of adding potassium chromate (K 2 CrO 4 ), sodium silicate (Na 2 SiO 3 ), and sodium vanadate (NaVO 3 ) to NaCl solution were examined using electrochemical methods on sensitized and solutionized AA5083 with and without the ASL present on the surface. The ASL alone may protect the alloy depending on whether or not the alloy was sensitized. All of the tested inhibitors exhibited a suppression of the cathodic reaction, with chromate causing mixed inhibition on sensitized AA5083 without the ASL present. The composition and surface morphology of samples exposed to inhibitors were also investigated. When β phase (Mg 2 Al 3 ) precipitates on the grain boundaries of AA5xxx (Al-Mg alloys), which can happen even at moderate temperatures over long periods of time, they become sensitized and susceptible to intergranular corrosion (IGC).1,2 Investigations into improving the corrosion properties of AA5xxx have focused on suppressing precipitation by alloying addition or changing the microstructure, 3-6 or on application of corrosion inhibitors. 7-15Aballe et al. studied the corrosion mechanism of the Al-Mg alloys in 3.5 wt% NaCl and concluded that localized corrosion results from the alkalinization around the cathodic sites, such as Fe-rich intermetallic particles in the metal matrix.7 Based upon this idea, inhibiting the cathodic reaction is expected to be a promising method to mitigate the corrosion on Al-Mg alloys. Chromates are cathodic inhibitors that have been widely used as pre-treatments of all aluminum alloys. 16 However, because chromates are toxic and carcinogenic, other inhibitors have been investigated. 17,18 Much research has been performed on the corrosion inhibition provided by rare earth element ions, which have been shown to provide good corrosion resistance by cathodic inhibition and to prevent localized corrosion of Al-Mg alloys. Aballe et al. and Bethencourt et al. showed that weight loss measurement results in 3.5 wt% NaCl solution decreased significantly with the addition of rare earth inhibitors. 9,10,14 Electrochemical impedance spectroscopy (EIS) was utilized to confirm the effect of CeCl 3 , by observing that the thickness of cerium in the compact film increased with exposure time. 8,19 Yasakau et al. used scanning Kelvin probe force microscopy (SKPFM) to investigate the dependence of the surface potential on the presence of cerium and lanthanide inhibitors. 20 The cathodic sites were preferent...

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Using EIS to analyse samples of Al–Mg alloy AA5083 treated by thermal activation in cerium salt baths

Cited by 42 publications

References 19 publications

Protection by Thermal and Chemical Activation with Cerium Salts of the Alloy AA2017 in Aqueous Solutions of NaCl

Protection by Thermal and Chemical Activation with Cerium Salts of the Alloy AA2017 in Aqueous Solutions of NaCl

Coatings for corrosion prevention based on rare earths

Corrosion Inhibition of Sensitized and Solutionized AA5083

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