Long-Term Atmospheric Corrosion Behavior of Alclad LC4 Aluminium Alloy
Abstract:
Atmospheric corrosion behaviors of alclad LC4 were investigated in rural, marine and industrial atmospheres in China for over 20 years.Corrosion weight loss and loss in mechanical properties were measured.Appearance, cross-section photomicrograph and corrosion products were observed and analyzed by SEM, EDS and FTIR.The results demonstrated that the weight loss was higher in industrial and marine atmospheres and lower in rural atmosphere.The relation of weight losses versus exposure time was linear approximately.Alclad LC4 still performed excellent mechanical properties after 20 years exposed in the three kinds of atmosphere, and the pitting did not penetrate the cladding of LC4.The corrosion products were all composed of hydrated aluminum hydroxide in industrial and marine atmospheres.
Fig.2 Loss in tensile strength and elongation of alclad LC4 exposed for 20 years at three sites
图3 带包铝层的LC4在3个试验站暴露20年后的表面腐蚀形貌
Fig.3 Appearances of alclad LC4 exposed for 20 years at three sites
(a) Front face at Beijing; (b) Back face at Beijing; (c) Front face at Jiangjin; (d) Back face at Jiangjin; (e) Front face at Wanning; (f) Back face at Wanning
图4 带包铝层的LC4暴露20年后的截面腐蚀形貌
Fig.4 Cross-section photomicrograph LC4 exposed for 20 years
(a) Front face at Beijing; (b) Back face at Beijing; (c) Front face at Jiangjin; (d) Back face at Jiangjin; (e) Front face at Wanning; (f) Back face at Wanning
Fig.5 EDS spectrums correspond to the inner layer cladding and outer layer cladding of alclad LC4 after 20 years exposure at Wanning
(a) Cross-sectional SEM morphology, alclad LC4 exposed for20 years exposure at the wanning test site; (b) EDS spectrum at the“D”point; (c) EDS spectrum at the“A”point
Fig.6 Cross-section photomicrograph of corrosion products exposed for 20 years
(a) Front face at Beijing; (b) Back face at Beijing; (c) Front face at Jiangjin; (d) Back face at Jiangjin; (e) Front face at Wanning; (f) Back face at Wanning
表2带包铝层的LC4在3个试验站暴露20年后表面腐蚀产物的化学成分
Table 2 Chemical compositions of corrosion products of alclad LC4 exposed for 20 years at three sites (%, mass fraction)
Sites
C
O
Na
Al
Si
S
Cl
K
Ca
Beijing
46.03
2.60
30.62
7.18
7.16
1.85
2.27
2.28
Jiangjin
16.50
59.05
12.24
5.26
6.13
0.54
0.28
Wanning
49.88
37.36
2.89
7.53
2.34
图7 带包铝层的LC4在江津和万宁试验站暴露20年后腐蚀产物的红外光谱
Fig.7 FTIR spectrums of corrosion products of alclad LC4 exposed for 20 years at Jiangjin and Wanning sites