Environmental Corrosion in Industrial-marine Atmosphere at Qingdao of 7050 Al-alloy Anodized in Boric- and Sulfuric-acid Electrolyte

doi:10.11902/1005.4537.2016.169

Journal of Chinese Society for Corrosion and protection

2016, Vol. 36

Issue (6): 580-586 DOI: 10.11902/1005.4537.2016.169

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Environmental Corrosion in Industrial-marine Atmosphere at Qingdao of 7050 Al-alloy Anodized in Boric- and Sulfuric-acid Electrolyte

Ziheng BAI^1,²,Yunhua HUANG^1,²,Xiaogang LI^1,^2,³,Lang YANG^1,²,Chaofang DONG^1,²,Lidan YAN^1,²,Kui XIAO^1,²(

)

1. Corrosion and Protection Center, University of Science and Technology Beijing, Beijing 100083, China
2. Institute of Advanced Materials and Technology, University of Science and Technology Beijing, Beijing 100083, China
3. Ningbo Institute of Material Technology & Engineering, Chinese Academy of Sciences, Ningbo 315201, China;

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Abstract

Corrosion behavior of 7050 Al-alloy, which was pre- anodized in electrolyte of boric-and sulfuric-acid, was assessed through field exposure in industrial-marine atmosphere for 2 a at Qingdao area. The corrosion rate was acquired from the relevant mass-lost data. The surface morphology, distribution of elements and the phase compositions of corrosion products were characterized by SEM, EDS and XRD, as well as the protectiveness of product scale and anodic film was evaluated by using EIS. It is indicated that the bare Al suffered from severe exfoliation corrosion with annual corrosion rate of 5.92 μma^-1, and its corrosion product mainly consists of Al(HSO₄)₃6H₂O, Al₄SO₄(OH)105H₂O and NaAlSi₃O₈; the formed corrosion product scale on the bare Al can provide protectiveness to the substrate to some extent, however, the anodized film can provide much better protectiveness in comparison with the formed oxide scale on bare Al.

Key words: atmospheric corrosion anodized aluminum alloy industrial marine atmosphere 7050 aluminum alloy

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	Ziheng BAI
	Yunhua HUANG
	Xiaogang LI
	Lang YANG
	Chaofang DONG
	Lidan YAN
	Kui XIAO

Cite this article:

Ziheng BAI,Yunhua HUANG,Xiaogang LI,Lang YANG,Chaofang DONG,Lidan YAN,Kui XIAO. Environmental Corrosion in Industrial-marine Atmosphere at Qingdao of 7050 Al-alloy Anodized in Boric- and Sulfuric-acid Electrolyte. Journal of Chinese Society for Corrosion and protection, 2016, 36(6): 580-586.

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https://www.jcscp.org/EN/10.11902/1005.4537.2016.169 OR https://www.jcscp.org/EN/Y2016/V36/I6/580

Table 1 Climatic parameters and atmospheric pollutants of Qingdao

Table 2 Corrosion rates of bare and anodized aluminumalloy in Qingdao atmosphere

Fig.1 Macroscopic morphologies of bare (a, c, e) and anodized (b, d, f) aluminum alloy samples after exposed for 0 a (a, b), 1 a (c, d) and 2 a (e, f)

Fig.2 Microscopic morphologies of corrosion products of bare (a, c) and anodized (b, d) aluminum alloysamples

Fig.3 Microscopic morphologies of bare (a) and anodized (b) aluminum alloy after removal of corrosion products

Table 3 Elements distribution of corrosion products in Fig.2 by EDS (atomic fraction / %)

Fig.4 XRD pattern of corrosion products on bare aluminumalloy after exposure for 2 a

Fig.5 Bode diagrams and fitted curves of bare (a) and anodized (b) aluminum alloy

Fig.6 Equivalent circuits of bare (a) and anodized (b) aluminum alloy for EIS analysis

Table 4 Fitting parameters of EIS equivalent circuit of bare and anodized aluminum alloy

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