Effect of Electrolyte in Microarc Oxidation on Providing Corrosion Resistance to Inhomogeneous Microstructure in ZM21 Magnesium Alloy

2019 ◽  
Vol 72 (6) ◽  
pp. 1617-1620
Author(s):  
V. Ram Kumar ◽  
V. Muthupandi
Keyword(s):  
Corrosion Resistance ◽  
Magnesium Alloy ◽  
Microarc Oxidation ◽  
Inhomogeneous Microstructure ◽  
Zm21 Magnesium Alloy

Corrosion Behavior of AZ31 Magnesium Alloy with Microarc Oxidation Film Irradiated by High-Intensity Pulsed Ion Beam

2008 ◽  
Vol 373-374 ◽  
pp. 460-463 ◽  
Author(s):  
X.G. Han ◽  
P. Li ◽  
X.P. Zhu ◽  
M.K. Lei
Keyword(s):  
Corrosion Resistance ◽  
Magnesium Alloy ◽  
High Intensity ◽  
Electrochemical Impedance ◽  
Ion Beam ◽  
Microarc Oxidation ◽  
Az31 Magnesium Alloy ◽  
Noticeable Improvement ◽  
Original Films ◽  
Sealing Layer

The microarc oxidation (MAO) films on AZ31 magnesium alloy were modified by high-intensity pulsed ion beam (HIPIB) at an ion current density of 200 A/cm2 with 1-5 shots. The modified MAO films presented a corrosion resistance superior to that of the original films. Scanning electron microscopy (SEM) observation revealed that a sealing layer was formed on the MAO films by HIPIB irradiation. The corrosion behaviors of the MAO films in 3.5 % NaCl solution were characterized by using electrochemical impedance spectroscopy (EIS). The noticeable improvement in the corrosion resistance of MAO films is attributed to the blocking effect of the sealing layer that hinders the process of electrolyte penetrating the MAO films to the magnesium alloy.

Effect of Duty Cycle on Microstructure and Corrosion Resistance of MAO Coatings Fabricated on AZ91D Magnesium Alloy in an Optimized Dual Electrolyte

2013 ◽  
Vol 668 ◽  
pp. 779-783 ◽  
Author(s):  
Shu Yan Wang ◽  
Yong Ping Xia ◽  
Li Liu ◽  
Qiao Chen
Keyword(s):  
Surface Roughness ◽  
Corrosion Resistance ◽  
Phase Composition ◽  
Magnesium Alloy ◽  
Coating Thickness ◽  
Duty Cycle ◽  
Microarc Oxidation ◽  
Ceramic Coatings ◽  
Relative Content ◽  
Az91d Magnesium Alloy

Ceramic coatings were fabricated on AZ91D magnesium alloy in a novel optimized dual electrolyte by Microarc oxidation. The influence of duty cycle on coating thickness, surface roughness, phase composition, microstructure and corrosion resistance were studied. It is found that both the thickness and surface roughness of coatings increases gradually with the increasing of duty cycle. XRD results show that all the coatings are mainly composed of MgO, Mg2SiO4 and MgAl2O4. The results of potentiodynamic polarization tests indicate that the coating formed at 40% duty cycle exhibits a better corrosion resistance as a result of its relatively compact microstructure and more relative content of Mg2SiO4 and MgAl2O4 phases.

Effects of Sodium Citrate on MAO Process and Characteristics of Coatings Fabricated on AZ91D Magnesium Alloy

2012 ◽  
Vol 502 ◽  
pp. 320-324 ◽  
Author(s):  
Shu Yan Wang ◽  
Yong Ping Xia ◽  
Li Liu
Keyword(s):  
Surface Roughness ◽  
Corrosion Resistance ◽  
Magnesium Alloy ◽  
Sodium Citrate ◽  
Electrochemical Impedance ◽  
Microarc Oxidation ◽  
Dense Layer ◽  
Cross Sectional ◽  
Az91d Magnesium Alloy ◽  
Thickness Meter

Microarc oxidation (MAO) coatings were prepared on AZ91D magnesium alloy in a novel dual electrolyte containing various concentrations of sodium citrate (C6H5Na3O7). The surface and cross-sectional morphologies, coating thickness and surface roughness were characterized by scanning electron microscopy (SEM), layer thickness meter and digital microscope, respectively. The corrosion resistance of coatings was evaluated by electrochemical impedance spectroscopy (EIS). The results showed that both the striking voltage and final voltage decreased gradually with the increase of C6H5Na3O7 concentration. When the C6H5Na3O7 concentration increased, surface roughness increased gradually, while thickness of the coating increased at first and then decreased. The coating formed in the electrolyte containing 5g/L C6H5Na3O7 had a much more uniform and compact microstructure with less micropores and micro-cracks. EIS test showed that the concentration of C6H5Na3O7 mainly affected the corrosion resistance of inner dense layer, and the coating with best corrosion resistance was obtained in the electrolyte containing 5g/L C6H5Na3O7.

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