scholarly journals Corrosion Resistance and Apatite-Forming Ability of Composite Coatings formed on Mg–Al–Zn–Ca Alloys

Materials ◽  
2019 ◽  
Vol 12 (14) ◽  
pp. 2262 ◽  
Author(s):  
Anawati Anawati ◽  
Hidetaka Asoh ◽  
Sachiko Ono
Keyword(s):  
Corrosion Resistance ◽  
Electrochemical Impedance ◽  
Galvanic Corrosion ◽  
Composite Coatings ◽  
Localized Corrosion ◽  
Electrolytic Oxidation ◽  
Eis Measurements ◽  
Plasma Electrolytic ◽  
Peo Coatings ◽  
Magnitude Improvement

The properties of composite coatings formed by plasma electrolytic oxidation (PEO) were affected by the alloy composition. The corrosion resistance and apatite-forming ability of PEO coatings formed on Mg–6Al–1Zn–xCa alloys with a variation of Ca content were investigated. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements showed an order magnitude improvement of corrosion resistance in the AZ61 alloy as a result of the coating. A higher enhancement in polarization resistance was obtained in the Mg–6Al–1Zn–1Ca and Mg–6Al–1Zn–2Ca alloys due to thicker coatings were formed as a result of the incorporation of calcium oxide/hydroxide. However, the underlying substrates were more prone to localized corrosion with increasing Ca content. The microstructure investigation revealed an enlargement in precipitates (Al2Ca, Mg2Ca) sizes with increasing Ca content in the alloys. The growth of larger size precipitates increased the danger to micro galvanic corrosion. Apatite layers were formed on all of the coatings indicating high apatite-forming ability, but the layers formed on the Mg–6Al–1Zn–1Ca and Mg–6Al–1Zn–2Ca alloys contained higher Mg, possibly due to the accumulation of corrosion product, than that on the Mg–6Al–1Zn alloy. The alloying element Ca should be limited to 1 wt.% as the excess tended to degrade the corrosion resistance and apatite-forming ability of the PEO coating.

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 Comparison of Biocompatible Coatings Produced by Plasma Electrolytic Oxidation on cp-Ti and Ti-Zr-Nb Superelastic Alloy

Coatings ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 401
Author(s):  
Ruzil Farrakhov ◽  
Olga Melnichuk ◽  
Evgeny Parfenov ◽  
Veta Mukaeva ◽  
Arseniy Raab ◽  
...  
Keyword(s):  
Plasma Electrolytic Oxidation ◽  
Electrochemical Impedance ◽  
Pure Titanium ◽  
Commercially Pure Titanium ◽  
X Ray ◽  
Kinetic Coefficients ◽  
Electrolytic Oxidation ◽  
Plasma Electrolytic ◽  
Cp Ti ◽  
Peo Coatings

The paper compares the coatings produced by plasma electrolytic oxidation (PEO) on commercially pure titanium and a novel superelastic alloy Ti-18Zr-15Nb (at. %) for implant applications. The PEO coatings were produced on both alloys in the identical pulsed bipolar regime. The properties of the coatings were examined using scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDX), potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS). The PEO process kinetics was modeled based on the Avrami theorem and Cottrell equation using a relaxation method. The resultant coatings contain TiO2, for both alloys, and NbO2, Nb2O5, ZrO2 for Ti-18Zr-15Nb alloy. The coating on the Ti-18Zr-15Nb alloy has a higher thickness, porosity, and roughness compared to that on cp-Ti. The values of the kinetic coefficients of the PEO process—higher diffusion coefficient and lower time constant for the processing of Ti-18Zr-15Nb—explain this effect. According to the electrochemical studies, PEO coatings on Ti-18Zr-15Nb alloy provide better corrosion protection. Higher corrosion resistance, porosity, and roughness contribute to better biocompatibility of the PEO coating on Ti-18Zr-15Nb alloy compared to cp-Ti.

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.

Electrodeposition and Hardness and Corrosion Resistance Propertie of Ni/Nano-B4C Composite Coatings

2011 ◽  
Vol 399-401 ◽  
pp. 2055-2060
Author(s):  
Ji Bo Jiang ◽  
Wei Dong Liu ◽  
Lei Zhang ◽  
Qing Dong Zhong ◽  
Yi Wang ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Electrochemical Impedance ◽  
Composite Coatings ◽  
Corrosion Property ◽  
Pure Nickel ◽  
Plating Bath ◽  
Tafel Polarization ◽  
Nickel Coatings ◽  
Eis Measurements ◽  
Steel Substrates

Ni–B4C composite coatings on carbon steel substrates with various contents of B4C nano-particulates were prepared by electrodeposition in Ni plating bath containing B4C nano-particulates. Microhardness, Scanning Electron Microscopy (SEM), Tafel polarization and Electrochemical Impedance Spectroscopy (EIS) measurements were used to compare pure nickel coatings and Ni–B4C composite coatings. Pure Ni coating microhardness is lower than that of Ni–B4C coatings and the microhardness of the composite coatings increases with the increase of the content of B4C nano-particulates. The effects of various contents of B4C nano-particulates on the corrosion resistance were investigated and it was found that the best anti–corrosion property of Ni–B4C composite coatings is at 6 g/L B4C in the bath formulation.

The Growth Process of the PEO Films under Escalating Voltage Waveform

2011 ◽  
Vol 239-242 ◽  
pp. 720-723
Author(s):  
Li Wang ◽  
Wen Fu ◽  
Li Chen
Keyword(s):  
Corrosion Resistance ◽  
Growth Process ◽  
Ceramic Coatings ◽  
Voltage Waveform ◽  
Potentiodynamic Polarization Curves ◽  
Initial Stage ◽  
Electrolytic Oxidation ◽  
Superior Corrosion Resistance ◽  
Plasma Electrolytic ◽  
Peo Coatings

In order to get a clear picture for describing the growth process of plasma electrolytic oxidation coatings under escalating voltage waveform, the characteristics of PEO coatings formed at different reaction stages were systemically investigated. The morphology and corrosion resistance of the films were studied by scanning electron microscope and potentiodynamic polarization curves. The uniform, semi-transparent and better corrosion resistance of the oxide films on the magnesium electrode surface were formed owe to the extended anodizing time at the initial stage under escalating voltage mode. After sparking occurred, generated ceramic coatings were brokedown, melted, cooled and solidified continuously, so the ceramic coatings were uniform and dense. It also exhibited superior corrosion resistance.

scholarly journals Fabrication and Characterization of Ceramic Coating on Al7075 Alloy by Plasma Electrolytic Oxidation in Molten Salt

Coatings ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 993
Author(s):  
Alexander Sobolev ◽  
Tamar Peretz ◽  
Konstantin Borodianskiy
Keyword(s):  
Corrosion Resistance ◽  
Molten Salt ◽  
Plasma Electrolytic Oxidation ◽  
Ceramic Coating ◽  
Electrochemical Impedance ◽  
Current Frequency ◽  
Electrolytic Oxidation ◽  
Fabrication And Characterization ◽  
Plasma Electrolytic

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.

scholarly journals TiO2Deposition on AZ31 Magnesium Alloy Using Plasma Electrolytic Oxidation

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Leon White ◽  
Youngmi Koo ◽  
Yeoheung Yun ◽  
Jagannathan Sankar
Keyword(s):  
Corrosion Resistance ◽  
Magnesium Alloy ◽  
Plasma Electrolytic Oxidation ◽  
Electrochemical Impedance ◽  
Protective Layer ◽  
Az31 Magnesium Alloy ◽  
Treatment Technique ◽  
Functional Coating ◽  
Electrolytic Oxidation ◽  
Plasma Electrolytic

Plasma electrolytic oxidation (PEO) has been used in the past as a useful surface treatment technique to improve the anticorrosion properties of Mg alloys by forming protective layer. Coatings were prepared on AZ31 magnesium alloy in phosphate electrolyte with the addition of TiO2nanoparticles using plasma electrolytic oxidation (PEO). This present work focuses on developing a TiO2functional coating to create a novel electrophotocatalyst while observing the surface morphology, structure, composition, and corrosion resistance of the PEO coating. Microstructural characterization of the coating was investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) followed by image analysis and energy dispersive spectroscopy (EDX). The corrosion resistance of the PEO treated samples was evaluated with electrochemical impedance spectroscopy (EIS) and DC polarization tests in 3.5 wt.% NaCl. The XRD pattern shows that the components of the oxide film include Mg from the substrate as well as MgO and Mg2TiO4due to the TiO2nanoparticle addition. The results show that the PEO coating with TiO2nanoparticles did improve the corrosion resistance when compared to the AZ31 substrate alloy.

scholarly journals Wear and Corrosion Resistance of Plasma Electrolytic Oxidation Coatings on 6061 Al Alloy in Electrolytes with Aluminate and Phosphate

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4037
Author(s):  
Zhenjun Peng ◽  
Hui Xu ◽  
Siqin Liu ◽  
Yuming Qi ◽  
Jun Liang
Keyword(s):  
Corrosion Resistance ◽  
Plasma Electrolytic Oxidation ◽  
Salt Spray ◽  
P Element ◽  
Alumina Coating ◽  
Al Alloy ◽  
Wear Properties ◽  
Electrolytic Oxidation ◽  
Plasma Electrolytic ◽  
Peo Coatings

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.

TEM Analysis and Corrosion Resistance of the Ceramic Coatings on Q235 Steel Prepared by Hybrid Method of Hot-Dipping Aluminum and Plasma Electrolytic Oxidation

2012 ◽  
Vol 152-154 ◽  
pp. 40-45
Author(s):  
Li Hong Lu ◽  
De Jiu Shen ◽  
Jing Wu Zhang ◽  
Chang Hong Guo
Keyword(s):  
Electron Microscopy ◽  
Corrosion Resistance ◽  
Hybrid Method ◽  
Plasma Electrolytic Oxidation ◽  
Sea Water ◽  
Composite Coatings ◽  
Ceramic Coatings ◽  
Q235 Steel ◽  
Electrolytic Oxidation ◽  
Plasma Electrolytic

The hybrid method of plasma electrolytic oxidation (PEO) and hot-dipping aluminum (HDA) was employed to deposit composite ceramic coatings on the surface of Q235 steel. The cross-section microstructure and surface morphology of the treated specimens were investigated with scanning electron microscopy (SEM). Especially, the composition of the composite coatings was investigated with transmission electron microscopy (TEM). The corrosion resistance was analyzed by immersing and corrosion polarizing experiments. The results indicate that metallurgical bonding can be observed between the ceramic coatings and the steel substrate. There are many micro-pores which act as discharge channels in the PEO coatings. The phase composition of the ceramic coatings is mainly composed of amorphous phase and crystal Al2O3 oxides. The crystal Al2O3 phase includes κ- Al2O3, θ- Al2O3 and β- Al2O3.The corrosion resistance of the PEO samples is much better than that of the HDA samples whether immersed in the NaCl solution or in the sea water.

Investigation of Plasma Electrolytic Oxidation of Magnesium Alloy under Pulse Power Supply

2013 ◽  
Vol 742 ◽  
pp. 143-146 ◽  
Author(s):  
Xiang Hua Song ◽  
Jian Hong Lu ◽  
Xij Jang Yin ◽  
Jian Ping Jiang ◽  
Annie Tan Lai Kuan
Keyword(s):  
Corrosion Resistance ◽  
Applied Voltage ◽  
Corrosion Current ◽  
Optimal Operation ◽  
Pulse Power ◽  
Coating Surface ◽  
Electrolytic Oxidation ◽  
Power Mode ◽  
Plasma Electrolytic ◽  
Peo Coatings

AZ31B magnesium alloys were treated by plasmaelectrolytic oxidation (PEO) technique using an environmental friendly electrolyte solution under single-polar pulse power mode to improve the coating performance. The effect of applied voltage on the coating qualities was studied. The coating surface and the cross-section morphology were characterized by scanning electron microscopy (SEM), and the corrosion resistance was tested by potentiodynamic polarization.The coating surface is porous, and the pore size in the coating layer grew with applied voltage increased. The potentiodynamic polarization tests showed that PEO coatings exhibit significantly improved corrosion resistance as compared with uncoated magnesium substrate AZ31B, decreasing the corrosion current density by three orders of magnitude. The anti-corrosion performance of the PEO coating was improved with the operation voltage increasing from 240 V to 280 V, and at voltage higher than 280 V, there is no further improvement on the coating electrochemical property. The optimal operation voltage was 280 V, which exhibits the most high corrosion resistance.

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