Influence of chloride ion concentration and temperature on the corrosion of Mg–Al alloys in salt fog

Merino, M.C.; Pardo, Á.; Arrabal, R.; Merino, S.; Casajús, P.; Mohedano, M.

doi:10.1016/j.corsci.2010.01.020

Cited by 149 publications

(87 citation statements)

References 28 publications

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“…The new insight includes elucidating the complex role played by the alloyed Al: (i) forming an enriched metallic layer at the intact film-substrate interface and (ii) incorporating into the intact film and aged corrosion filaments. Both aspects have been argued to be beneficial from a corrosion resistance perspective: the enriched metallic layer providing a more tortuous path for Mg dissolution, 30,31,[37][38][39][40][41][42][43][44][45][46][47][48][49] and its incorporation into the film reducing the film growth rate. [30][31][32] Interestingly, neither was effective in preventing the corrosion filaments from initiating on and propagating across the AM30 surface during immersion.…”

Section: Discussionmentioning

confidence: 99%

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Cathodic Activity of Corrosion Filaments Formed on Mg Alloy AM30

Cano

McDermid

Kish

2015

J. Electrochem. Soc.

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The filiform-like corrosion of extruded Mg alloy AM30 immersed in a dilute near-neutral NaCl solution was investigated using electrochemical techniques coupled with transmission electron microscopy (TEM). Scanning vibrating electrode technique (SVET) measurements showed that the filament-like corrosion consisted of an intensely anodic propagation front supported by a cathodicallyactivated filament behind. The TEM examination of the corroded and intact surface films in cross-section using thin foils prepared by focused-ion-beam (FIB) milling indicated that the cathodic activity was likely a combined result of the formation of a thick, highly-defective MgO film and the ability of Al-Mn intermetallic particles to catalyze the cathodic H 2 gas evolution reaction. The formation of an Al-rich layer at the film/alloy interface with time, due to the incongruent dissolution of the alloy, was not able to stop the initiation and propagation of the filaments. Mg and Mg alloys have been shown to be susceptible to the formation of laterally-spreading products, which tend to manifest as thread-like "filaments" or radially-expanding "discs" during corrosion in aqueous NaCl solutions. [1][2][3][4][5][6][7][8][9][10][11][12] Williams et al. have offered critical insights into the electrochemical mechanism of this unique localized corrosion mode on pure Mg 1,5,7 and the Mg-Al-Zn-Mn alloy AZ31B 9 by employing the scanning vibrating electrode technique (SVET), where their SVET measurements showed that the corrosion filaments/discs became cathodically-activated following their formation. It was proposed that the net cathode on the locally corroded regions galvanically coupled with the adjacent intensely anodic regions to drive the lateral propagation of the corrosion products across the exposed surface. The formation of discs versus filaments was suggested to depend on whether the catalytic efficiency of the locally corroded region allowed for galvanic coupling with its perimeter, or merely along the most anodic pathways of the microstructure.7 This "differential electrocatalytic" mechanism was also shown to drive filiform corrosion on coated Mg as determined by scanning Kelvin probe (SKP) measurements. 1The mechanism, however, by which the cathodic reaction (H 2 gas evolution) is enhanced on corroded Mg or Mg alloys continues to be unclear. Proposed mechanisms include (i) the enrichment of noble secondary phase constituents such as iron (Fe) impurity particles (for pure Mg) or Al-Mn intermetallic particles (for AZ31B) within the corroded regions 5,9,13,14 (ii) an increased catalytic tendency of the corroded regions caused either by undissolved metallic Mg "chunks," 15 a significantly roughened surface film 5 or the formation of Mg(OH) 2 as a corrosion product. 16 The SVET measurements reported by Williams et al. suggested that a significantly reduced cathodic activation was exhibited by the as-cast AZ31B corrosion filaments 9 relative to the corrosion discs on pure Mg.5 This finding agrees well with the noble secondary phase theory,...

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Section: Discussionmentioning

confidence: 99%

“…[37][38][39][40] Danie et al 40 examined this layer formed on Al-rich eutectic Mg grains of AM50 (Mg-4.4%Al-0.3%Mn) in some detail using low-loss and core-loss electron loss energy spectroscopy (EELS). They observed a sharp plasmon peak characteristic of the metallic state from the Al-enriched layer.…”

Section: Discussionmentioning

confidence: 99%

Cathodic Activity of Corrosion Filaments Formed on Mg Alloy AM30

Cano

McDermid

Kish

2015

J. Electrochem. Soc.

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“…Corrosion attack of Mg, AZ31, AZ80 and AZ91D materials under the salt fog tests increased with increasing temperature and chloride ion concentration [7]. Individual pitting characteristics, including pit surface area and pit volume, were greater for the salt spray surfaces [8]. Usually, the second phase in traditional Mg alloys consists of binary alloy such as Mg17Al12 & AlMn.…”

Section: Introductionmentioning

confidence: 99%

Effect of chloride ion concentration, spraying time and pH values on corrosion behavior of friction stir welded AZ61A magnesium alloy welds in salt fog environments

Dhanapal¹,

Boopathy²,

Balasubramanian³

2013

uujms

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The present research devoted to the investigation of the corrosion behavior of AZ61A FSW welds in accelerated conditions, including the influence of salt fog environmental parameters such as chloride ion concentration, pH, and duration of exposure. Significant numbers of tests were carried out that make possible to create the regression model (empirical equation) of influence of selected environmental parameters on corrosion rate. The corrosion products were analyzed by SEM and XRD analysis. This research demonstrates the effect of chloride ion concentrations, spraying time and pH values on corrosion rate, and it show the corrosion activity decelerates with the increasing pH value and spraying time respectively. It was found that the increase in chloride ion concentration accelerates the corrosion of AZ61A weldments. The corrosion morphology was predominantly influenced by the distribution of β-phase (e.g. Mg17Al12 intermetallic).

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“…Merino et al [16] have reported the corrosion attack of Mg, AZ31, AZ80 and AZ91D materials under the salt fog test increased with increasing temperature and Clˉ concentration. Individual pitting characteristics, including pit surface area and pit volume, were greater for the salt spray surfaces.…”

Section: Introductionmentioning

confidence: 99%

“…From the literature review [16][17][18][19][20], it is understood that most of the published information on corrosion behavior of Mg alloys were focused on general corrosion and pitting corrosion of magnesium alloys. Moreover, there is no literature available related to prediction of corrosion rate of magnesium alloys under salt fog environment by means of an empirical relationship incorporating chloride ion concentration, pH value, spraying time, and air pressure.…”

Section: Introductionmentioning

confidence: 99%

Prediction of corrosion rate of AZ31B magnesium alloy under salt fog environment in NaCl solution

even>D.Thirumalaikumarasamy¹,

Shanmugam²,

Balasubramanian³

2013

uujms

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Magnesium alloys have gained considerable interest as a material for automotive and aerospace applications due to its low density, high specific strength, and good castability. However, another considerable issue is their corrosion properties. This restricts their practical applications. In this present research, corrosion behavior of the AZ31B magnesium alloy was evaluated by conducting salt fog test in NaCl solution at different chloride ion concentrations, pH values, spraying times, and air pressures. The corrosion morphology observation was carried out by optical microscopy and the corrosion products were analyzed by SEM and XRD analysis. An attempt was also made to develop an empirical relationship to predict the corrosion rate of AZ31B magnesium alloy. Four factors five level central composite rotatable design matrix was used to minimize the number of experimental conditions. Response surface (RSM) methodology was used to develop the relationship. The developed relationship can be effectively used to predict the corrosion rate of AZ31B magnesium alloy at 95% confidence level.

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Influence of chloride ion concentration and temperature on the corrosion of Mg–Al alloys in salt fog

Cited by 149 publications

References 28 publications

Cathodic Activity of Corrosion Filaments Formed on Mg Alloy AM30

Cathodic Activity of Corrosion Filaments Formed on Mg Alloy AM30

Effect of chloride ion concentration, spraying time and pH values on corrosion behavior of friction stir welded AZ61A magnesium alloy welds in salt fog environments

Prediction of corrosion rate of AZ31B magnesium alloy under salt fog environment in NaCl solution

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