Chloride Ion Effects in the Corrosion Kinetics of Intermetallics in Acidic Solutions

Ito, C.; Nobe, Ken

doi:10.1149/1.3229969

Cited by 5 publications

(5 citation statements)

References 7 publications

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“…4,14 It has been shown that the perchlorate (ClO 4 − ) anions tend to complex less with the surface metal atoms as compared to chloride anions (Cl − ). 15 As a result perchlorate ions are less corrosive than chloride anions but still cause localized pitting corrosion on magnesium alloys (in a similar fashion to Cl − ions). 14 The chosen electrolyte for this investigation is 0.1M sodium perchlorate (NaClO 4 ) as to allow sufficient conductivity, reduce the corrosion rates, prevent tip blockage, and allow longer time periods for investigation.…”

Section: Resultsmentioning

confidence: 99%

Corrosion Mechanisms in Dissimilar AZ31/AZ80 Friction Stir Welds

Savguira

North

Thorpe

2018

J. Electrochem. Soc.

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Corrosion of dissimilar friction stir welds (FSW) made in AZ31/AZ80 magnesium alloys was investigated using the scanning reference electrode technique (SRET), and microcapillary polarization technique, complemented by optical and SEM/EDX microscopy. The corrosion rate of the base metals along with the welded specimen was estimated by mass loss testing. The stir zone material in both alloys showed a higher corrosion potential than the base metal due to the partial dissolution of β-Mg 17 Al 12 and Al-Mn particles. The basic corrosion mechanism in dissimilar welds was determined to be different from that of a similar joint. The corrosion behavior of the dissimilar FSW joint was governed by the galvanic coupling of the two alloys, and not by the microstructural evolution occurring during the welding process. The corrosion behavior of the joint was governed by the galvanic coupling between the α-Mg matrix in AZ31 and the Al-rich intermetallics in AZ80. The welded specimens exhibited the highest corrosion rate, while AZ80 was the most corrosion resistant material. Magnesium alloys can be successfully joined by friction stir welding (FSW) to achieve excellent mechanical integrity in completed welds. 1,2 One challenge arising from the utilization of this joining method is an increased susceptibility to localized corrosion in the material immediately adjacent to the welded joint. 3-6 Previous microcapillary polarization and scanning reference electrode technique (SRET) studies have revealed that the stir zones in AZ31B spot and seam welds are more cathodic than the bulk material. [3][4][5][6] Due to the difference in electrochemical potentials, a macrogalvanic cell is formed causing pitting corrosion in the thermo-mechanically affected zone (TMAZ) and the heat affected zone (HAZ) regions, which are located between the noble stir zone and the active base metal. 5 The differences in the electrochemical behavior of different regions in completed joints have been related to their microstructural evolution that occurred during the welding operation. The stir zone microstructure comprised a dynamically recrystallized matrix which was nominally devoid of intermetallics. The increase in the corrosion potential of the stir zone has been attributed to the dissolution of β-Mg 17 Al 12 and Al-Mn particles via two mechanisms: 4,5 1. Dissolution of intermetallics, which increases the concentration of Al in the α-Mg matrix, resulting in a higher corrosion potential of this region, 7 and 2. The absence of the intermetallics, which eliminates the microgalvanic coupling between the intermetallic particles (IMPs) and the α-Mg matrix, and reduces the susceptibility of the welded joint to localized pitting corrosion. [8][9][10][11] Many industrial applications require joining of dissimilar alloys, and therefore it is essential to understand the influence of the welding process on the corrosion behavior of dissimilar joints. It is currently unknown whether the corrosion behavior of dissimilar welds is governed by the microstructural changes o...

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Section: Resultsmentioning

confidence: 99%

Corrosion Mechanisms in Dissimilar AZ31/AZ80 Friction Stir Welds

Savguira

North

Thorpe

2018

J. Electrochem. Soc.

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“…Its corrosion in chloride-containing environments has been studied even less. Such studies have been carried out to investigate antimony as a part of intermetallic compounds [29], galvanic coupled to carbon steel [30] as well as in connection with the development of binary intermetallic compounds and antifriction composite materials [31].…”

Section: Introductionmentioning

confidence: 99%

Corrosion behaviour of heterogeneous antimony-copper layers in chloride media

Tzaneva,

Kostov

2023

Corrosion Engineering, Science and Technology: The Internationa

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The electrodeposited antimony-copper coatings demonstrate a varying degree of chemical and structural heterogeneity that determines their corrosion behaviour in 0.5M sodium chloride. The electrochemical and corrosion properties of layers at open circuit potential were investigated by electrochemical impedance spectroscopy and optical surface observation. Corrosion polarisation tests revealed that anodic behaviour of Sb-Cu alloys is similar for the all tested samples and depends on the antimony chemical resistance. Under anodic polarisation up to about −0.03 V Ag/AgCl a multistep process of anodic oxide film transformation was registered. The observations by SEM revealed that at a higher anodic polarisation many submicron-sized pits are formed. The formation of microgalvanic corrosion cells results in preferential dissolution of the antimony phase at both OCP and anodic polarisation.

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“…Our previous study [2,4] showed that, when alloyed potentiostatically, the uppermost surface of the resultant Cu-Sn phase depends on the potential during the alloying: The main phase obtained at +5 mV vs. Sn 2+ /Sn 0 is Cu 6 Sn 5 intermetallic compound, while that at +20 mV is Cu 3 Sn. In other words, this process will be a convenient tool to compare various surface properties of these two intermetallic phases.…”

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“…The electrochemical deposition of alloys and compounds is a fundamental technology for thin-layer processing in the fields of, for example, surface finishing and electronic materials. Recently, we have demonstrated that Cu-Sn alloy layers with composition of 40-60 wt.% Sn can be formed by an electrochemical reductiondiffusion (RD) method using galvanic contact [1][2][3] or potentiostatic [2,4] technique. The target Cu-Sn alloy called "speculum metal" appears silver-gray and has been investigated as a promising hypoallergenic coating to replace Ni underlayer for Cr or Au electroplating.…”

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confidence: 99%

“…Although this metallization requires two steps to obtain the alloy layer, the consecutive use of two baths containing a single-metal component can simplify the waste bath treatment. In the RD process, solid-state interdiffusion of the two metal components is important; hence, we employed nonvolatile and nonflammable hydrophobic ionic liquids, trimethyl-nhexylammonium bis[(trifluoromethyl)sulfonyl]amide (TMHA-Tf 2 N) [1,2] and 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]amide (EMI-Tf 2 N) [3,4], as green solvents for the RD process at 110-190 ˚C.…”

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confidence: 99%

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