Supporting Information

© Wiley-VCH 2008

69451 Weinheim, Germany

Supporting Information for

Corrosion Resistance of Superhydrophobic Layered Double Hydroxide Films

on Aluminum

Fazhi Zhang, Lili Zhao, Hongyun Chen, Sailong Xu, David G. Evans and Xue Duan*

State Key Laboratory of Chemical Resource Engineering,

Beijing University of Chemical Technology, Beijing, China,100029

Email:duanxbuct@163.com

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(a)

(b)

(c)

(d) (e)

100μm 100μm

100μm 100 μm

5μm 100μm 5μm

100μm

2μm

100μm

2μm

100μm

2μm

100μm 100μm 100μm

0 days 12 days 21 days

Figure S1. SEM micrographs of samples before and after immersion in 3.5%

aqueous sodium chloride solution for different times at room temperature: (a) bare

Al substrate, (b) PAO/Al film, (c) ZnAl-LDH-NO3– film, (d) PAO/Al-laurate film, and

(e) ZnAl-LDH-laurate film. 2

Figure S2. Cross-section SEM image of the ZnAl-LDH-laurate hybrid film

showing the continuous polycrystalline LDH coating under its surface.

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1mm 1mm

(a) (b)

Figure S3. SEM images of (a) ZnAl-LDH-NO3– film, and (b) ZnAl-LDH-laurate

film after testing for adhesion. The samples were treated according to the method

reported by Beving et al. (D. E. Beving, A. M. P. McDonnell, W. S. Yang, Y. S. Yan,

J. Electrochem. Soc. 2006, 153, B325.)

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The anti-corrosion coating of the superhydrophobic LDHs film has also been applied

to aluminum alloys, which usually have small amount of other elements, such as Cu,

Mg, and Fe, making the corrosion problems much worse. As shown in Figures S4 and

S5, a ZnAl-LDH-NO3– film can be formed directly on the aluminum alloy substrate.

After treatment with a solution of sodium laurate, an anion-exchange reaction of

laurate with the ZnAl-LDH-NO3– film occurred, affording a ZnAl-LDH-laurate film with

many microscale hemispherical protrusions on its surface. The film possesses highly

superhydrophobic properties with a water contact angle of about 150°. DC

polarization measurements (Figure S6) show that the superhydrophobic LDH-laurate

hybrid film exhibits current densities as low as 10-8 A/cm2, providing much better

corrosion resistance than the LDH-nitrate film. The above experimental data illustrate

that the film formation can be repeated successfully on an aluminum alloy and

broadens the potential range of applications of the film.

10 20 30 40 50 60 70

I(CP

S)

2 theta/deg

a

b

c

003

006009

0024

0027

003006

Figure S4. XRD patterns of (a) aluminum alloy, (b) ZnAl-LDH-NO3– precursor film

with aluminum alloy as substrate, and (c) ZnAl-LDH-laurate hybrid film on

aluminium alloy substrate.

5

200μm 5μm

200μm 20μm

(a) (b)

(c) (d)

Figure S5. SEM images of (a) the ZnAl-LDH-NO3– film with aluminum alloy as

substrate at low magnification, (b) the ZnAl-LDH-NO3– film at high magnification, (c)

the ZnAl-LDH-laurate hybrid film showing the hemispherical protrusions, and (d) a

high magnification image of a hemispherical protrusion.

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Figure S6. Polarization curves of samples immersed in 3.5% aqueous sodium

chloride solution at room temperature for 30 minutes: (a) ZnAl-LDH-NO3– film with

aluminum alloy as substrate, and (b) ZnAl-LDH-laurate film.

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Table S1 XRD peak positions and relative intensities for the ZnAl-LDH-laurate film

Miller indices, hkl 2 θ/o I/Io (%)

003 2.511 10

006 5.089 3

009 7.686 3

0018 14.307 4

0021 17.253 4

0024 20.757 100

0027 23.060 18

012 34.995 11

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Table S2 Chemical composition for aluminum alloy AA2024

Si Fe Cu Mn Mg Zn Ti Ni

0.50 0.50 3.80-4.90 0.30-0.90 1.20-1.80 0.30 0.15 0.10

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