Effect of carbon nanotubes on microstructure and corrosion resistance of PEO ceramic coating of magnesium alloy

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Qun Ma ◽  
Ping Wang ◽  
Xiaomin Chen ◽  
Chunqing Zhang
Keyword(s):  
Carbon Nanotubes ◽  
Corrosion Resistance ◽  
Ceramic Coating ◽  
Film Formation ◽  
Formation Rate ◽  
Corrosion Current ◽  
Plasma Discharge ◽  
Test System ◽  
Electrochemical Test ◽  
Plasma Electrolytic

Abstract Plasma electrolytic oxidation (PEO) ceramic coating modified by carbon nanotubes (CNTs) was prepared on Mg–Gd–Y alloy. The microstructure, hydrophobicity and corrosion resistance of the coating were investigated by SEM, contact angle meter and electrochemical test system. Carbon nanotubes (CNTs) are staggered in the ceramic coating and partially filled with plasma discharge micropores. To some extent, CNTs can promote the plasma discharge and improve the film formation rate. With the increase of the content of CNTs, the content of carbon nanotubes in the ceramic coating increases. CNTs can effectively improve the hydrophobicity of ceramic coating. With the increase of the content of CNTs, the corrosion potential E coor and polarization resistance R p increase, the corrosion current i coor decreases and the AC impedance |Z| increases, which leads to the decrease of corrosion rate.

scholarly journals Applying Baghdadite/PCL/Chitosan Nanocomposite Coating on AZ91 Magnesium Alloy to Improve Corrosion Behavior, Bioactivity, and Biodegradability

Coatings ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 789 ◽  
Author(s):  
Farzad Soleymani ◽  
Rahmatollah Emadi ◽  
Sorour Sadeghzade ◽  
Fariborz Tavangarian
Keyword(s):  
Corrosion Resistance ◽  
Biomedical Applications ◽  
Corrosion Current Density ◽  
Ceramic Coating ◽  
Alloy Coating ◽  
Corrosion Current ◽  
Nanocomposite Coating ◽  
Az91 Alloy ◽  
Az91 Magnesium Alloy ◽  
Az91 Magnesium

Magnesium alloys have received a great amount of attention regarding being used in biomedical applications; however, they show high degradability, poor bioactivity, and biocompatibility. To improve these properties, surface modification and various types of coatings have been applied. In this study, an anodized AZ91 alloy was coated with a polymer matrix composite made of polycaprolactone/chitosan (PCL/Ch) with different percentages of baghdadite to improve its resistance to corrosion, bioactivity, and biocompatibility. The effects of different percentages of baghdadite (0 wt %, 1 wt %, 3 wt %, and 5 wt %) on the surface microstructure, corrosion resistance, roughness, and wettability were evaluated. The results indicated that the applied nano-polymer-ceramic coating including 3 wt % baghdadite was hydrophobic, which consequently increased the corrosion resistance and decreased the corrosion current density of the anodized AZ91 alloy. Coating with 3 wt % baghdadite increased the roughness of AZ91 from 0.329 ± 0.02 to 7.026 ± 0.31 μm. After applying the polymer-ceramic coating on the surface of anodized AZ91, the corrosion products changed into calcium–phosphate compounds instead of Mg(OH)2, which is more stable in a physiological environment.

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 Study on the Wear and Seawater Corrosion Resistance of Ni–Co–P Alloy Coatings with Jet Electrodeposition in Different Jet Voltages and Temperatures of Plating Solution

Coatings ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 639
Author(s):  
Yin Zhang ◽  
Min Kang ◽  
Liang Yao ◽  
Nyambura Samuel Mbugua ◽  
Meifu Jin ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Corrosion Current ◽  
X Ray Diffraction ◽  
Electrochemical Test ◽  
Maximum Value ◽  
Seawater Corrosion ◽  
Jet Electrodeposition ◽  
Plating Solution ◽  
Xrd Patterns ◽  
Steel Substrates

In order to improve the wear and seawater corrosion resistance of metals, Ni–Co–P alloy coatings were fabricated on 45 steel substrates with jet electrodeposition in different jet voltages and temperatures of plating solution. The cross-section morphology, chemical composition, crystalline structure, microhardness, wear, and seawater corrosion resistance of the samples were analyzed and characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), microhardness tester, friction wear tester, and electrochemical workstation, respectively. The results showed that the contents of Co in Ni–Co–P alloy coatings changed with the variation of jet voltages and temperature of plating solution. The content of Co in Ni–Co–P alloy coatings reached a maximum value of 47.46 wt·% when the jet voltage was 12 V and the temperature of the plating solution was 60 °C. The XRD patterns of Ni–Co–P alloy coatings showed that there was an obvious preferred orientation in the (111) plane. With an increase in the jet voltages and temperature of the plating solution, the microhardness of Ni–Co–P alloy coatings first increased and then decreased, with the maximum value obtained being 634.9 HV0.1. When the jet voltage was 12 V and the temperature of the plating solution was 60 °C, the wear scar width of the Ni–Co–P alloy coatings reached a minimum value of 463.4 µm. In addition, the polarization curves in the electrochemical test indicated that the samples deposited at 60 °C and 12 V exhibited the lowest corrosion current density (Icorr) of 1.72 µA/cm2 and highest polarization resistance (Rp) of 19.61 kΩ·cm−2, which indicated that the coatings had better seawater corrosion resistance.

Influence of Triethylamine Inhibitor Addition on the Sealing Process of 6063 Al Alloy

2012 ◽  
Vol 538-541 ◽  
pp. 230-234
Author(s):  
Hui Cheng Yu ◽  
Xiao Xiao Huang ◽  
Yan Yan Han ◽  
Dong Ping Wei
Keyword(s):  
Corrosion Resistance ◽  
Corrosion Potential ◽  
Electrochemical Impedance ◽  
Corrosion Current ◽  
Al Alloy ◽  
Test Results ◽  
Electrochemical Test ◽  
Tafel Polarization ◽  
Electrochemical Parameters ◽  
6063 Al Alloy

To improve the corrosion resistance of Al alloy, triethylamine (TEN) was added into the sealing solutions. Tafel polarization and electrochemical impedance spectroscopy(EIS) techniques were used to investigate the electrochemical behavior of sealing coatings formed in different concentrations of triethylamine(TEN). Compared with the coatings with D. I. water and the bare aluminum alloy, the polarization curves show that the sealing coatings formed in 5.0 – 7 .0 g.L-1 triethylamine (TEN) solutions have more positive corrosion potential (Ecorr) and pitting corrosion potential (Epit), and lower corrosion current density (icorr). Electrochemical parameters of EIS indicate that the sealing coatings have higher corrosion resistance. The electrochemical test results show the prepared sealing coatings have better corrosion resistance.

In Situ Formation of ZrO2-Y2O3-Containing Ceramic Coating on Magnesium Alloy by Plasma Electrolytic Oxidation

2011 ◽  
Vol 295-297 ◽  
pp. 1684-1690
Author(s):  
Hai He Luo ◽  
Qi Zhou Cai
Keyword(s):  
Corrosion Resistance ◽  
Magnesium Alloy ◽  
Plasma Electrolytic Oxidation ◽  
Ceramic Coating ◽  
Electrochemical Corrosion ◽  
Dense Layer ◽  
X Ray ◽  
Electrolytic Oxidation ◽  
Plasma Electrolytic

A ZrO2-Y2O3-containing composite ceramic coating was firstly in situ prepared on AZ91D magnesium alloy by plasma electrolytic oxidation (PEO) technique in an alkaline silicate-containing electrolyte. The morphology, chemical composition and corrosion resistance of the PEO coating were investigated by environmental scanning electron microscopy (ESEM), X-ray diffractometer (XRD), energy dispersive X-ray (EDX) spectrometer, dropping corrosion and electrochemical corrosion test. The results showed that the ceramic coating consisted of two distinct structural layers: an outer loose layer and an inner dense layer; it was composed of t-ZrO2, Y2O3, SiO2and some magnesium compounds, such as MgO,MgF2and Mg2SiO4. In addition, the ceramic coating also showed excellent dropping and electrochemical corrosion resistance, which was mainly attributed to its special phase composition and microstructure.

Enhancement of Corrosion Resistance of PEO Coating on AZ91 Biomedical Magnesium Alloy by Surface Laser Treating

2013 ◽  
Vol 365-366 ◽  
pp. 1110-1113 ◽  
Author(s):  
Miao Wang ◽  
Yun Long Wang ◽  
Zhong De Liu ◽  
Hua Ding
Keyword(s):  
Corrosion Resistance ◽  
Magnesium Alloy ◽  
Plasma Electrolytic Oxidation ◽  
Ceramic Coating ◽  
Alloy Sample ◽  
Corrosion Tests ◽  
Coating Surface ◽  
Electrolytic Oxidation ◽  
Surface Laser ◽  
Plasma Electrolytic

Ceramic coating was fabricated on AZ91 biomedical magnesium alloy by plasma electrolytic oxidation. The coating was then subjected to surface laser treating, and the influence of laser treating on the morphologies and corrosion resistance of the coating were investigated. The results showed that PEO coating without laser treating showed coarse and porous surface and the pores on coating surface were big. When subjected to laser treating, the pores on coating surface became little and few. The corrosion tests in SBF indicated that corrosion resistance of PEO coating on magnesium alloy sample could improve the corrosion resistance of the substrate, and surface laser treating could further increase the corrosion resistance.

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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