Corrosion Resistance of Superhydrophobic Mg-Al Layered Double Hydroxide Coatings on Aluminum Alloys

doi:10.1007/s40195-015-0335-4

Abstract

Abstract:

A superhydrophobic surface was successfully constructed to modify the layered double hydroxide (LDH) coatings on aluminum alloy using stearic acid. The characteristics of the coatings were investigated using SEM, XRD, FT-IR and XPS. The corrosion resistance of the prepared coatings was studied using potentiodynamic polarization and electrochemical impedance spectrum. The results revealed that the superhydrophobic surface considerably improved the corrosion-resistant performance of the LDH coatings on the aluminum alloy substrate. The formation mechanism of the superhydrophobic surface was proposed.

Key words: Aluminum alloy, Layered double hydroxide, Superhydrophobic, Stearic acid, Corrosion

Fen Zhang, Chang-Lei Zhang, Liang Song, Rong-Chang Zeng, Lan-Yue Cui, Hong-Zhi Cui. Corrosion Resistance of Superhydrophobic Mg-Al Layered Double Hydroxide Coatings on Aluminum Alloys[J]. Acta Metallurgica Sinica (English Letters), 2015, 28(11): 1373-1381.

Figures/Tables 12

Fig. 1 XRD patterns of the bare aluminum alloy substrate and LDH coatings formed on aluminum alloy

Fig. 2 Surface morphologies of the samples with different coatings of original LDH coating a, SA1-LDH coating b, SA2-LDH coating c and SA3-LDH coating d, and the cross-sectional microstructure of LDH coating e

Fig. 3 Photographs of water droplets on the surface of different samples: a bare aluminum alloy; b LDH coating; c SA1-LDH coating; d SA2-LDH coating; e SA3-LDH coating

Fig. 4 XPS survey spectra of SA2-LDH coating a, and high-resolution XPS spectra in Al2p b, C1s c, O1s d and Mg1s e spectral regions

Fig. 5 FT-IR spectra of the LDH coating a and SA1-LDH coating b, SA2-LDH coating c and SA3-LDH coating d

Fig. 6 Polarization curves of the AA50005 substrate and the samples coated with the original and modified LDH coatings in 3.5 wt% NaCl solution

Table 1 Corrosion potential (E corr) and corrosion current density (I corr) of the samples related to the polarization curves in Fig. 6

Sample	E _corr (V_vs.SCE)	I _corr (μA cm^-2)
AA5005 substrate	-1.15	13.5
Original LDH coating	-1.08	0.794
SA1-LDH coating	-1.01	0.0457
SA2-LDH coating	-0.98	0.0251
SA3-LDH coating	-0.95	0.0398

Fig. 7 EIS spectra of the AA50005 substrate and the samples coated with the original and modified LDH coatings in 3.5 wt% NaCl solution: a Bode plots of |Z| versus frequency; b Nyquist plots; c enlarged plots of b

Fig. 8 EIS spectra of the modified LDH coatings before and after immersion in 3.5 wt% NaCl solution for 72 h: a Bode plots of |Z| versus frequency; b Nyquist plots; c Bode plots of phase angle versus frequency

Fig. 9 Photographs of water droplets on SA1-LDH coating a, SA2-LDH coating b, SA3-LDH coating c after 72 h immersion tests in 3.5 wt% NaCl solution

Fig. 10 Morphologies of bare AA5005 substrate a, the LDH coatings b and the superhydrophobic surface c after immersion for 21 days in 3.5 wt% NaCl aqueous solution

Fig. 11 Schematic representation of the formation of a superhydrophobic surface on the LDH-coated AA5005 Al alloy: a formation of a LDH coating; b hydrophobic modification of the LDH coating; c formation of a superhydrophobic coating

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