Abstract
NiAl-layered double hydroxide (NiAl-LDH) coatings grown in-situ on AZ31 Mg alloy were prepared for the first time utilizing a facile hydrothermal method. The surface morphologies, structures, and compositions of the NiAl-LDH coatings were characterized by scanning electron microscopy (SEM), three dimensional (3D) optical profilometer, X-ray diffractometer (XRD), Fourier transform infrared spectrometer (FT-IR), and X-ray photoelectron spectroscopy (XPS). The results show that NiAl-LDH coating could be successfully deposited on Mg alloy substrate using different nickel salts, i.e., carbonate, nitrate, and sulfate salts. Different coatings exhibit different surface morphologies, but all of which exhibit remarkable enhancement in corrosion protection in 3.5 wt % NaCl corrosive electrolyte. When nickel nitrate was employed especially, an extremely large impedance modulus at a low frequency of 0.1 Hz (|Z|f = 0.1 Hz), 11.6 MΩ cm2, and a significant low corrosion current density (jcorr) down to 1.06 nA cm−2 are achieved, demonstrating NiAl-LDH coating’s great potential application in harsh reaction conditions, particularly in a marine environment. The best corrosion inhibition of NiAl-LDH/CT coating deposited by carbonate may partially ascribed to the uniform and vertical orientation of the nanosheets in the coating.
Highlights
Mg alloy has excellent physical and mechanical properties but a high chemical reactivity and susceptibility to corrosion, which hinders its practical application and development in more fields [1]
The NiAl-Layered double hydroxides (LDHs) coating prepared by nickel carbonate exhibits uniformly and vertically aligned nanoarrays with an extremely large impedance modulus at a low frequency of 0.1 Hz (|Z|f = 0.1 Hz), 11.6 MΩ cm2, and a significantly low jcorr down to 1.06 nA cm−2 in 3.5 wt % NaCl corrosive electrolyte, which outperforms the values of the foregoing achieved LDH coating on Mg alloy (Table 1) [8,10,13,14,16,17,18]
All the NiAl-LDH coatings obtained by different nickel salts show remarkable enhancement in corrosion inhibition in NaCl solution compared with Mg alloy substrate, which is attributed to the strongly affinity between charge-compensating CO32− and brucite-like layers
Summary
Mg alloy has excellent physical and mechanical properties but a high chemical reactivity and susceptibility to corrosion, which hinders its practical application and development in more fields [1]. The NiAl-LDH coating prepared by nickel carbonate exhibits uniformly and vertically aligned nanoarrays with an extremely large impedance modulus at a low frequency of 0.1 Hz (|Z|f = 0.1 Hz), 11.6 MΩ cm, and a significantly low jcorr down to 1.06 nA cm−2 in 3.5 wt % NaCl corrosive electrolyte, which outperforms the values of the foregoing achieved LDH coating on Mg alloy (Table 1) [8,10,13,14,16,17,18]. The NiAl-LDH coating prepared by nickel carbonate exhibits uniformly and vertically aligned nanoarrays with an extremely large impedance modulus at a low frequency of 0.1 Hz (|Z|f = 0.1 Hz), 11.6 MΩ cm, and a significantly low jcorr down to 1.06 nA cm−2 in 3.5 wt % NaCl corrosive electrolyte, which outperforms the values of the foregoing achieved LDH coating on Mg alloy (Table Nanomate1ri)als[82,01108,1, 38,,1441,116–18]. The NiAl-LDH coatings were characterized, and the enhanced corrosion inhibition mechanism was proposed and discussed
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