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Atmospheric corrosion of aluminium alloy 2024-T3 exposed to salt lake environment in Western China

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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

[pic 15]

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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