Influence of microstructure and composition on the corrosion behaviour of Mg/Al alloys in chloride media

Pardo, Á.; Merino, M.C.; Coy, A.E.; Viejo, F.; Arrabal, R.; Feliú, S.

doi:10.1016/j.electacta.2008.06.001

Cited by 320 publications

(164 citation statements)

References 42 publications

Supporting

Mentioning

148

Contrasting

Unclassified

Order By: Relevance

“…Finally, when the exposure time increased even further (43 hours) the corrosion resistance of both alloys increased due to the presence of the quasipassive film, and the overall number of bubbles decreased. 12,17 The bubbles that remained on the surface were preferentially located on the AZ80 side, with some preference being given to sites near the dissimilar interface. Similar observations were made on the corresponding uncoupled based metals ( Figure 9).…”

Section: Resultsmentioning

confidence: 99%

“…These results correspond with the electrochemical output during polarization testing of AZ31 and AZ80 in 3.5 wt% NaCl. 17,18 Padro et al postulated that the effect of aluminum alloying on the corrosion resistance properties of magnesium alloys was related to two discrete mechanisms. 17,18 The higher aluminum content in AZ80 increased the volume fraction and size of β-Mg 17 Al 12 intermetallic particles that acted as a barrier to the progression of the corrosion attack.…”

Section: Resultsmentioning

confidence: 99%

“…17,18 Padro et al postulated that the effect of aluminum alloying on the corrosion resistance properties of magnesium alloys was related to two discrete mechanisms. 17,18 The higher aluminum content in AZ80 increased the volume fraction and size of β-Mg 17 Al 12 intermetallic particles that acted as a barrier to the progression of the corrosion attack. 18 The higher aluminum content in the matrix of AZ80 also facilitated the formation of a semi-protective oxide layer enriched in aluminum.…”

Section: Resultsmentioning

confidence: 99%

See 2 more Smart Citations

Corrosion Mechanisms in Dissimilar AZ31/AZ80 Friction Stir Welds

Savguira

North

Thorpe

2018

J. Electrochem. Soc.

View full text Add to dashboard Cite

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...

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Corrosion Mechanisms in Dissimilar AZ31/AZ80 Friction Stir Welds

Savguira

North

Thorpe

2018

J. Electrochem. Soc.

View full text Add to dashboard Cite

show abstract

“…It has been shown that the eutectic (α +β) and α-Mg (matrix) phases have different aluminium contents [23,26]. These dissimilar aluminium distributions give rise to different corrosion behaviours: areas with aluminium concentrations of less than approximately 8 % have been found to be more prone to corrosion attack than areas with higher amounts of aluminium or areas containing the β-phase [13].…”

Section: Introductionmentioning

confidence: 99%

“…The influence of intermetallic phases on the corrosion behaviour of magnesium alloys has been investigated in a number of papers [4, 13, 14, 16-21, 23-30, 32, 33]. It has been shown that an increase in Al content (8-9 wt%) significantly improves the corrosion resistance of these alloys [23]. The AZ91 alloy consists of two intermetallic phases: β-Mg 17 Al 12 and η-Al 8 Mn 5 .…”

Section: Introductionmentioning

confidence: 99%

The use of a multiscale approach in electrochemistry to study the corrosion behaviour of as-cast AZ91 magnesium alloy

Kot

Krawiec

2015

J Solid State Electrochem

View full text Add to dashboard Cite

The microstructure of as-cast AZ91 alloy is complex, with the presence of Mg 17 (Al, Zn) 12 precipitates surrounded by an eutectic phase, AlMn intermetallic particles and an α-Mg solid solution. In addition, the distribution of aluminium in the alloy was found to be heterogeneous. Under these conditions, a multiscale approach coupling global and local electrochemical measurements seems to be a promising method to study its corrosion behaviour. Results show that the multiscale approach can be used in 0.1 M NaCl. In this case, AZ91 is susceptible to pitting corrosion. By contrast, the multiscale approach is not valid for AZ91 in 0.1 M Na 2 SO 4 . At the global scale, filiform corrosion and pitting corrosion are observed in the matrix, whereas only pits initiate when using the microcapillary techniques. The obtained results show that the local electrochemical techniques have to be used carefully in some environments.

show abstract