Effects of Disodium Phosphate Concentration (Na2HPO4·2H2O) on Microstructure and Corrosion Resistance of Plasma Electrolytic Oxidation (PEO) Coatings on 2024 Al Alloy

2018 ◽  
Vol 27 (2) ◽  
pp. 825-834 ◽  
Author(s):  
Arash Fattah-alhosseini ◽  
Seyed Omid Gashti ◽  
Maryam Molaie
Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4037
Author(s):  
Zhenjun Peng ◽  
Hui Xu ◽  
Siqin Liu ◽  
Yuming Qi ◽  
Jun Liang

Phosphate and aluminate electrolytes were used to prepare plasma electrolytic oxidation (PEO) coatings on 6061 aluminum alloy. The surface and cross-section microstructure, element distribution, and phase composition of the PEO coatings were characterized by SEM, EDS, XPS, and XRD. The friction and wear properties were evaluated by pin-on-disk sliding tests under dry conditions. The corrosion resistance of PEO coatings was investigated by electrochemical corrosion and salt spray tests in acidic environments. It was found that the PEO coatings prepared from both phosphate and aluminate electrolytes were mainly composed of α-Al2O3 and γ-Al2O3. The results demonstrate that a bi-layer coating is formed in the phosphate electrolyte, and a single-layered dense alumina coating with a hardness of 1300 HV is realizable in the aluminate electrolyte. The aluminate PEO coating had a lower wear rate than the phosphate PEO coating. However, the phosphate PEO coating showed a better corrosion resistance in acidic environment, which is mainly attributed to the presence of an amorphous P element at the substrate/coating interface.


2012 ◽  
Vol 550-553 ◽  
pp. 1969-1975 ◽  
Author(s):  
Xi Di Chen ◽  
Qi Zhou Cai ◽  
Li Song Yin

Plasma electrolytic oxidation (PEO) ceramic coatings were prepared on 6061 aluminum alloy substrate in silicate based electrolyte with and without Na2WO4additive with different pulse frequency. The composition, surface morphology and corrosion resistance of PEO coatings were investigated by means of SEM, XRD, potentiodynamic polarization and EIS measurement in a 3.5% NaCl solution. These results show that Na2WO4can contributing to the transition from the metastable γ-Al2O3to a better thermal stability α-Al2O3, while has certain inhibitory effect on the deposition of SiO32-anion on the surface during the plasma discharge process. After adding Na2WO4in the electrolyte, the surface layer of PEO coatings are more smoother and less distinctly discharge holes appear which leads to the PEO coatings have better corrosion resistance than those of samples coated in the electrolyte without Na2WO4additive.


Materials ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 2438 ◽  
Author(s):  
Myungwon Hwang ◽  
Wonsub Chung

Plasma electrolytic oxidation (PEO) coating was obtained on AZ31 Mg alloy using a direct current in a sodium silicate-based electrolyte with and without a carbon nanotube (CNT) additive. The surface morphology and phase composition of the PEO coatings were investigated through field emission scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The corrosion-resistance properties of the PEO coatings were evaluated using potentiodynamic polarization measurements and electrochemical impedance spectroscopy (EIS) in a 3.5 wt.% NaCl solution. Furthermore, the heat-dissipation property was evaluated by a heat-flux measurement setup using a modified steady-state method and Fourier transform infrared spectroscopy (FT-IR). The results demonstrate that, by increasing the concentration of CNT additive in the electrolyte, the micropores and cracks of the PEO coatings are greatly decreased. In addition, the anticorrosion performance of the PEO coatings that incorporated CNT for the protection of the Mg substrate was improved. Finally, the coating’s heat-dissipation property was improved by the incorporation of CNT with high thermal conductivity and high thermal emissivity.


Coatings ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 111
Author(s):  
Marta Mohedano ◽  
Beatriz Mingo

The demand of modern technological society for light structural materials (Al, Ti, Mg) emphasizes a combination of good corrosion resistance with wear properties and functionalized surfaces [...]


Author(s):  
Daniel Kajanek ◽  
Branislav Hadzima ◽  
Matej Brezina ◽  
Martina Jackova

Impact of applied current density during the plasma electrolytic oxidation (PEO) process on corrosion resistance of AZ31 magnesium alloy was studied. The PEO coatings were prepared using four different current densities with values of 0.025 A/cm2, 0.05 A/cm2, 0.1 A/cm2 and 0.15 A/cm2 in electrolyte consisting of 10 g/l Na 3PO4.12H2O and 1 g/l KOH. Morphology and chemical composition of the coatings was examined using the scanning electron microscopy and EDS analysis respectively. Electrochemical characteristics of ground and coated samples were measured by means of electrochemical impedance spectroscopy (EIS) in 0.1M NaCl solution. Obtained data in form of Nyquist diagrams were analysed by equivalent circuit method. Results of experiments showed that value of applied current density had significant effect on protective performance of the PEO coatings prepared on AZ31 magnesium alloy surface.


2020 ◽  
Vol 67 (1) ◽  
pp. 48-58
Author(s):  
Wanying Liu ◽  
Junjie Yang ◽  
Yuhong Qiu ◽  
Ying Liu ◽  
Kuanhai Deng

Purpose The preferable concentration of titanium carbide was optimized and added as an additive to the micro-arc oxidation electrolyte to produce a high corrosion-resistant coating on D16T aluminum alloy. Design/methodology/approach Ceramic coatings were deposited on D16T aluminum alloy by plasma electrolytic oxidation in alkaline silicate electrolytes with micron titanium carbide particle suspending at different concentrations. Influences of additive concentration on morphology, elemental and phase composition and corrosion resistance of doped PEO coatings were evaluated by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and electrochemical methods, respectively. Findings Results revealed that suspending titanium carbide additives incorporated into ceramic coatings through discharging channels and chemically transformed into amorphous stage. The content of titanium in the doped coatings increased with the increasing concentration of suspending micron additive. Compared with the coating without particle addition, the corrosion resistance of the coating produced in 8 g/L titanium carbide suspension increased more than 20 times. The result indicated that the incorporation of titanium into the PEO coatings formed on the D16T aluminum alloy could effectively improve the corrosion resistance. Originality/value The mechanism of corporation of TiC and the mechanism of improving the corrosion resistance of the coating were proposed.


2017 ◽  
Vol 724 ◽  
pp. 435-442 ◽  
Author(s):  
Nastaran Barati ◽  
Aleksey Yerokhin ◽  
Farhad Golestanifard ◽  
Saeid Rastegari ◽  
Efstathios I. Meletis

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