Atmospheric corrosion of aluminium alloy 2024-T3 exposed to salt lake environment in Western China
Por: tondsl • 9/9/2015 • Artigo • 8.271 Palavras (34 Páginas) • 379 Visualizações
Corrosion Science 59 (2012) 63–70[pic 5]
Atmospheric corrosion of aluminium alloy 2024-T3 exposed to salt lake environment in Western China
B.B. Wang, Z.Y. Wang ⇑, W. Han, W. Ke[pic 6]
State Key Laboratory for Corrosion and Protection, Institute of Metal Research, Chinese Academy of Sciences, Wencui Road 62, Shenyang 110016, PR China[pic 7][pic 8]
a r t i c l e i n f o [pic 9]
Article history:
Received 20 August 2011
Accepted 21 February 2012
a b s t r a c t
Atmospheric corrosion of aluminium alloy 2024-T3 exposed to salt lakes environment for 6 years was investigated by weight loss, analysis of morphology and corrosion products. The results showed an increase in the mass loss with a high rate in the first 2 years, and tended to stabilise over time. A main
Available online 28 February 2012[pic 10][pic 11]
crystalline component of corrosion products, ½Mg1 x
Alx ðOHÞ2
Cl
mH2 O, was determined by XRD.
Keywords:
A. Aluminium
B. XRD
C. Atmospheric corrosion
C. Stress corrosion[pic 12]
Besides pitting and intergranular corrosion, stress corrosion cracks (SCC) were observed in all test peri- ods. According to the analysis, causes for the corrosion behaviour were attributed to the deposition of salts particles (mainly MgCl2 6H2O) and the arid climate.
2012 Elsevier Ltd. All rights reserved.[pic 13]
1. Introduction
Aluminium and its alloys have been extensively used outdoors, especially in the fields of transport, building, electrical engineering, aircraft and aerospace. In those fields, aluminium and its alloys are usually exposed in various atmospheric environments and they can be affected by different forms of atmospheric corrosion like pitting corrosion, intergranular corrosion and even stress corrosion.
In the past decades, the weather exposure tests of aluminium and its alloys have been performed in different atmosphere all over the world by many countries [1–13]. Most of these field tests are performed in high contamination (mainly Cl , SO2) atmospheric environments with high relative humidity (>80% RH), as well as large numbers of laboratory-simulated tests [14–21]. However, few studies have focused on arid and salt-rich atmosphere with characteristics of low relative humidity (<50% RH, even about
30% RH) and high contamination (mainly Cl ). The salt lake zone is a typical representative of arid and salt-rich environments. Salt lakes are widely distributed on the globe and are mainly located in arid and semi-arid areas [22].
Since salt lakes are abundant in mineral resources (for example, salt lakes hold more than 70% of world lithium reserves in store which is a key point for development of Li battery) [22], many countries pay more and more attention to the development and utilisation of salt lakes including China. Characteristics of salt lake atmosphere are extremely dry and high salt content which are different from those of desert atmosphere and marine[pic 14]
⇑ Corresponding author. Tel./fax: +86 24 2389 3544.
E-mail address: zhywang@imr.ac.cn (Z.Y. Wang).
atmosphere [23]. As a result of the particularity, metals exposed in salt lake atmosphere suffered special corrosion behaviours [6,9,12]. It was shown that in arid and salt-rich atmosphere, the cor- rosion rate of carbon steels were much lower than that in other typ- ical climate areas in a preliminary corrosion survey in Western China. On the contrary, stainless steels and aluminium suffered much more severe corrosion (even more severe than marine envi- ronment and acid rain environment) and was simply attributed to the high salts deposited.
Meanwhile, different from seawater, some salt lakes are abun- dant in magnesium ions, such as the Dead Sea, the Chaerhan salt lake [22]. However, except for studies on the effect of NaCl, investi- gations of the influence of other cations like Mg2+ on the corrosion of metals are scarce. Furthermore, few laboratory investigations in controlled environments provide discrepancy results about the effect of different cations [19–21]. Blücher et al. investigated the corrosion of aluminium exposed to high relative humidity (95%) environments with NaCl, MgCl2 salts particles deposited, and con- cluded that in the presence of carbon dioxide, the corrosion induced by the salts studied exhibited similar rates and no corrosion prod- ucts containing magnesium element were observed [19]. Zheng et al. studied the atmospheric corrosion of aluminium deposited with different soluble salts using a laboratory-accelerated test of cyclic wet–dry. It was found that due to its lower deliquescence rel- ative humidity (DRH) which extended time of wetness, MgCl2 had stronger influence on atmospheric corrosion of aluminium than NaCl [20].
Therefore, the corrosiveness of the salt lake atmosphere for com- mon metals has drawn enormous attention. However, it is scarce of system research on corrosion laws and mechanism of metals
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0010-938X/$ - see front matter 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.corsci.2012.02.015
exposed in salt lake atmosphere. At present, atmospheric corrosion studies on common metals for 8 years have been carried out around the Chaerhan salt lake since it is the biggest salt lake in China and has been developed for a long time [24–26]. In this work, a field exposure test of aluminium alloy 2024-T3 in salt lake atmosphere for 6 years has been performed to investigate the influence of arid climate and salts deposited on the atmospheric corrosion.
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