scholarly journals Effect of K2ZrF6 Concentration on the Two-Step PEO Coating Prepared on AZ91 Mg Alloy in Alkaline Silicate Solution

Materials ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 499
Author(s):  
Zeeshan Ur Rehman ◽  
Bon Heun Koo ◽  
Yeon-Gil Jung ◽  
Je Hyun Lee ◽  
Dongjin Choi
Keyword(s):  
Corrosion Resistance ◽  
Plasma Electrolytic Oxidation ◽  
Layer Structure ◽  
Silicate Solution ◽  
Granular Structure ◽  
Az91d Alloy ◽  
Surface Porosity ◽  
Electrolytic Oxidation ◽  
Plasma Electrolytic ◽  
Step Parameters

In this study, a two-step Plasma Electrolytic Oxidation (PEO) method with constant primary step parameters and varying K2ZrF6 concentration in the secondary electrolyte solution was carried out to obtain a hard and dense coating on AZ91D alloy. For lower concentrations of K2ZrF6, a mixture of granular and pancake structure with higher surface porosity was obtained. Increasing the concentration up to 6 g/L caused the granular structure to disappear and a significant decrease was observed in the surface porosity as well as inner layer damage. Due to the compact inner layer structure, significant improvement in the corrosion resistance and mechanical properties of the AZ91 was observed with K2ZrF6 concentration. Highest values of hardness and corrosion resistance, i.e., 1589.45 HV and 386.30 × 103 Ω cm2, respectively, were obtained for a 6 g/L K2ZrF6 concentration.

scholarly journals Surface Modification of Aluminum 6061-O Alloy by Plasma Electrolytic Oxidation to Improve Corrosion Resistance Properties

Coatings ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 4
Author(s):  
Dmitry V. Dzhurinskiy ◽  
Stanislav S. Dautov ◽  
Petr G. Shornikov ◽  
Iskander Sh. Akhatov
Keyword(s):  
Corrosion Resistance ◽  
Aluminum Alloy ◽  
Aluminum Alloys ◽  
Plasma Electrolytic Oxidation ◽  
Electrochemical Impedance ◽  
High Strength ◽  
Electrolytic Oxidation ◽  
Coating Layers ◽  
Plasma Electrolytic ◽  
High Strength Aluminum Alloys

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.

scholarly journals Effects of a Carbon Nanotube Additive on the Corrosion-Resistance and Heat-Dissipation Properties of Plasma Electrolytic Oxidation on AZ31 Magnesium Alloy

Materials ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 2438 ◽  
Author(s):  
Myungwon Hwang ◽  
Wonsub Chung
Keyword(s):  
Corrosion Resistance ◽  
Carbon Nanotube ◽  
Plasma Electrolytic Oxidation ◽  
Heat Dissipation ◽  
X Ray ◽  
Steady State Method ◽  
Electrolytic Oxidation ◽  
Plasma Electrolytic ◽  
Dissipation Property ◽  
Peo Coatings

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.

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