Atmospheric corrosion of field-exposed magnesium alloy AZ91D

Jönsson, Martin; Persson, Dan; Leygraf, Christofer

doi:10.1016/j.corsci.2007.12.005

Cited by 89 publications

(70 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…15 According to Jönsson et al, 40,41 who investigated the NaCl-induced atmospheric corrosion of MgAl alloys, micro-galvanic elements are established where the anodic dissolution mainly occurs in the middle of the primary α-dendrite grains and the cathodic process mainly occurs on the intermetallic phases, i.e. β and η particles.…”

Section: Discussionmentioning

confidence: 99%

Effect of Rheocasting on Corrosion of AM50 Mg Alloy

Esmaily

Mortazavi

Shahabi-Navid

et al. 2014

J. Electrochem. Soc.

View full text Add to dashboard Cite

The corrosion behavior of magnesium-aluminum (Mg-Al) alloy AM50 produced by a rheocasting (RC) technique was examined in the presence and absence of CO 2 at three temperatures −4, 4 and 22 • C. The slurry preparation in the RC material was performed with the newly developed RheoMetal process. For reference, 99.97% Mg was included in the corrosion exposures. The influence of the microstructure on the atmospheric corrosion of alloy AM50 produced by RC and high pressure die casting (HPDC) was investigated. The RC AM50 alloy showed better corrosion resistance than HPDC AM50 in all the exposure environments studied. For both materials, there was a strong positive correlation between temperature and the atmospheric corrosion rate. The superior atmospheric corrosion behavior of RC AM50 compared to HPDC AM50 is carefully discussed in relation to differences in the as-cast microstructure. This study demonstrates that producing the alloy AM50 by this type of RC technique opens the door to Mg-Al alloys as a promising candidate for various applications where corrosion resistance is of importance. Magnesium-aluminum (Mg-Al) alloys are being employed in the automotive and many other engineering sectors owing to their high specific strength, high specific stiffness, good castability and recycleability, excellent machinability and abundant resources.1-4 Thus, they offer several advantages from the weight reduction and energy savings points of view. However, the more widespread use of MgAl alloys is limited by their low corrosion resistance and poor high temperature mechanical properties. [5][6][7][8] The corrosion properties of MgAl alloys have therefore attracted scientific attention. Currently, the majority of Mg-Al cast components are produced by conventional high-pressure die casting (HPDC). One of the main problems of thickwalled Mg-Al components made by HPDC is the relatively high fraction of porosity caused by the turbulent die filling. The pores function as local stress concentrators and can severely degrade mechanical properties and porosity also interferes with the heat-treatment of cast components. 9,10 Semi-solid casting is an alternative manufacturing technique that can be used to produce castings with a high level of complexity. In this process, a semi solid slurry is used, which shows non-turbulent or thixotropic flow behavior. Semi-solid cast alloys offer some advantages over their HPDC counterparts. For instance, porosity is lower due to laminar mould-filling and lower solidification shrinkage. 11,12Thixo-forming and rheocasting (RC) are the main semi-solid manufacturing processes. In thixo-forming, a near-net shape forming process is achieved using a partially melted, non-dendritic alloy slug. 12In contrast, RC involves preparation of a semi-solid slurry from the liquid alloy by cooling. In the RheoMetal process (also called the RSF process or the Rapid S process) cooling is performed by using an enthalphy exchange material (EEM) attached to a stirrer. 13 Thus, the metal is cooled internally which eliminates t...

show abstract

Section: Discussionmentioning

confidence: 99%

Effect of Rheocasting on Corrosion of AM50 Mg Alloy

Esmaily

Mortazavi

Shahabi-Navid

et al. 2014

J. Electrochem. Soc.

View full text Add to dashboard Cite

show abstract

“…In a very thin film the electric field is enormous, but as the film thickens the effect of the electric field is reduced and the growth rate soon falls to a very low value. 4 The thickness of the film formed in air on magnesium-based materials is initially around 2-3 nm, and can slowly increase up to some 4-7 nm after months of exposure at room temperature [1,3,4,30,32]. The surface composition of this oxide film can change significantly during ambient storage.…”

Section: Introductionmentioning

confidence: 99%

“…The surface composition of this oxide film can change significantly during ambient storage. Extra layers of hydrated and carbonated products of the magnesium oxide can be added to the original oxide film [1,3,32], and an increase in water molecules in the film has been reported for long ambient exposure times [33]. Hydrophobic organic-matter can also be picked up from the atmosphere [ 3 ].…”

Section: Introductionmentioning

confidence: 99%

Effect of naturally formed oxide films and other variables in the early stages of Mg-alloy corrosion in NaCl solution

Feliú

Maffiotte

Samaniego

et al. 2011

Electrochimica Acta

View full text Add to dashboard Cite

“…The anodic reaction (Mg dissolution) under a thin electrolyte layer is diminished compared to a bulk electrolyte [13]. Additionally, the main cathodic process in solution is water reduction, while oxygen reduction is the main cathodic reaction during atmospheric corrosion in thin electrolyte layers [14,15]. The overall rate of corrosion and nature of corrosion products are strongly influenced by the RH and chloride ion concentration.…”

Section: Interaction Of Mg and Its Alloys With The Atmospherementioning

confidence: 99%

Magnesium-Based Sacrificial Anode Cathodic Protection Coatings (Mg-Rich Primers) for Aluminum Alloys

Pathak

Mendon

Blanton

et al. 2012

Metals

View full text Add to dashboard Cite

Abstract:Magnesium is electrochemically the most active metal employed in common structural alloys of iron and aluminum. Mg is widely used as a sacrificial anode to provide cathodic protection of underground and undersea metallic structures, ships, submarines, bridges, decks, aircraft and ground transportation systems. Following the same principle of utilizing Mg characteristics in engineering advantages in a decade-long successful R&D effort, Mg powder is now employed in organic coatings (termed as Mg-rich primers) as a sacrificial anode pigment to protect aerospace grade aluminum alloys against corrosion. Mg-rich primers have performed very well on aluminum alloys when compared against the current chromate standard, but the carcinogenic chromate-based coatings/pretreatments are being widely used by the Department of Defense (DoD) to protect its infrastructure and fleets against corrosion damage. Factors such as reactivity of Mg particles in the coating matrix during exposure to aggressive corrosion environments, interaction of atmospheric gases with Mg particles and the impact of Mg dissolution, increases in pH and hydrogen gas liberation at coating-metal interface, and primer adhesion need to be considered for further development of Mg-rich primer technology.

show abstract

Atmospheric corrosion of field-exposed magnesium alloy AZ91D

Cited by 89 publications

References 9 publications

Effect of Rheocasting on Corrosion of AM50 Mg Alloy

Effect of Rheocasting on Corrosion of AM50 Mg Alloy

Effect of naturally formed oxide films and other variables in the early stages of Mg-alloy corrosion in NaCl solution

Magnesium-Based Sacrificial Anode Cathodic Protection Coatings (Mg-Rich Primers) for Aluminum Alloys

Contact Info

Product

Resources

About