Cathodic voltage-dependent composition, microstructure and corrosion resistance of plasma electrolytic oxidation coatings formed on Zr-4 alloy

RSC Advances ◽  
2016 ◽  
Vol 6 (41) ◽  
pp. 34616-34624 ◽  
Author(s):  
Yu Wang ◽  
Hui Tang ◽  
Rui Wang ◽  
Yongqiang Tan ◽  
Haibin Zhang ◽  
...  

We innovatively regulated the content of t-ZrO2 and m-ZrO2 in the plasma electrolytic oxidation coatings by adjusting the cathodic voltage.

Coatings ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 4
Author(s):  
Dmitry V. Dzhurinskiy ◽  
Stanislav S. Dautov ◽  
Petr G. Shornikov ◽  
Iskander Sh. Akhatov

In the present investigation, the plasma electrolytic oxidation (PEO) process was employed to form aluminum oxide coating layers to enhance corrosion resistance properties of high-strength aluminum alloys. The formed protective coating layers were examined by means of scanning electron microscopy (SEM) and characterized by several electrochemical techniques, including open circuit potential (OCP), linear potentiodynamic polarization (LP) and electrochemical impedance spectroscopy (EIS). The results were reported in comparison with the bare 6061-O aluminum alloy to determine the corrosion performance of the coated 6061-O alloy. The PEO-treated aluminum alloy showed substantially higher corrosion resistance in comparison with the untreated substrate material. A relationship was found between the coating formation stage, process parameters and the thickness of the oxide-formed layers, which has a measurable influence on enhancing corrosion resistance properties. This study demonstrates promising results of utilizing PEO process to enhance corrosion resistance properties of high-strength aluminum alloys and could be recommended as a method used in industrial applications.


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 ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 993
Author(s):  
Alexander Sobolev ◽  
Tamar Peretz ◽  
Konstantin Borodianskiy

The fabrication of a ceramic coating on the metallic substrate is usually applied to achieve the improved performance of the material. Plasma electrolytic oxidation (PEO) is one of the most promising methods to reach this performance, mostly wear and corrosion resistance. Traditional PEO is carried out in an aqueous electrolyte. However, the current work showed the fabrication and characterization of a ceramic coating using PEO in molten salt which was used to avoid disadvantages in system heating-up and the formation of undesired elements in the coating. Aluminum 7075 alloy was subjected to the surface treatment using PEO in molten nitrate salt. Various current frequencies were applied in the process. Coating investigations revealed its surface porous structure and the presence of two oxide layers, α-Al2O3 and γ-Al2O3. Microhardness measurements and chemical and phase examinations confirmed these results. Potentiodynamic polarization tests and electrochemical impedance spectroscopy revealed the greater corrosion resistance for the coated alloy. Moreover, the corrosion resistance was increased with the current frequency of the PEO process.


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