scholarly journals Improvement of AZ91 Alloy Corrosion Properties by Duplex NI-P Coating Deposition

Materials ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1357 ◽  
Author(s):  
Jaromír Wasserbauer ◽  
Martin Buchtík ◽  
Jakub Tkacz ◽  
Stanislava Fintová ◽  
Jozef Minda ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Magnesium Alloy ◽  
Corrosion Behavior ◽  
Electrochemical Impedance ◽  
Salt Spray ◽  
Az91 Alloy ◽  
Neutral Salt ◽  
Az91 Magnesium Alloy ◽  
Corrosion Properties ◽  
Az91 Magnesium

The corrosion behavior of duplex Ni-P coatings deposited on AZ91 magnesium alloy was studied. The electroless deposition process of duplex Ni-P coating consisted in the preparation of low-phosphorus Ni-P coating (5.7 wt.% of P), which served as a bond coating and high-phosphorus Ni-P coating (11.5 wt.% of P) deposited on it. The duplex Ni-P coatings with the thickness of 25, 50, 75 and 100 µm were deposited on AZ91 magnesium alloy. The electrochemical corrosion behavior of coated AZ91 magnesium alloy was investigated by electrochemical impedance spectroscopy and potentiodynamic polarization method in 0.1 M NaCl. Obtained results showed a significant improvement in the corrosion resistance of coated specimens when compared to uncoated AZ91 magnesium alloy. From the results of the immersion tests in 3.5 wt.% NaCl, 10% solution of HCl and NaOH and 5% neutral salt spray, a noticeable increase in the corrosion resistance with the increasing thickness of the Ni-P coating was observed.

scholarly journals Sealing of PEO Coated AZ91 Magnesium Alloy Using La-Based Solutions

2017 ◽  
Vol 2017 ◽  
pp. 1-13 ◽  
Author(s):  
Luca Pezzato ◽  
Katya Brunelli ◽  
Riccardo Babbolin ◽  
Paolo Dolcet ◽  
Manuele Dabalà
Keyword(s):  
Corrosion Resistance ◽  
Magnesium Alloy ◽  
Photoelectron Spectroscopy ◽  
Az91 Alloy ◽  
Az91 Magnesium Alloy ◽  
Corrosion Properties ◽  
X Ray ◽  
Different Temperatures ◽  
Az91 Magnesium ◽  
Sealing Treatment

In this work, solutions containing lanthanum salts were used for a post-treatment of sealing to increase the corrosion resistance of PEO coated AZ91 alloy. PEO coatings were produced on samples of AZ91 magnesium alloy using an alkaline solution containing sodium hydroxide, sodium phosphates, and sodium silicates. The sealing treatment was performed in a solution containing 12 g/L of La(NO3)3at pH 4 at different temperatures and for different treatment times. Potentiodynamic polarization test, an EIS test, showed that the sealing treatment with solution containing lanthanum nitrate caused a remarkable increase in the corrosion resistance. The corrosion behavior was correlated with the surface morphology and elemental composition evaluated with scanning electron microscope (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). In particular, the sealing treatment at 50°C for 30 min resulted in being the most promising to increase the corrosion properties of PEO treated samples because of the formation of a homogeneous sealing layer, mainly composed of La(OH)3.

Ceria Coatings Prepared by Sol-Gel Approach on AZ91 Magnesium Alloy

2017 ◽  
Vol 898 ◽  
pp. 1369-1380 ◽  
Author(s):  
Hui Min Han ◽  
Dan Tong Wang ◽  
Hua Qian Yu ◽  
Min Zuo ◽  
Li Hong Wang ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Corrosion Resistance ◽  
Magnesium Alloy ◽  
Sol Gel ◽  
Electrochemical Corrosion ◽  
Chemical Conversion ◽  
Corrosion Current ◽  
Az91 Alloy ◽  
Az91 Magnesium Alloy ◽  
Az91 Magnesium

The ceria coatings on AZ91 substrates were successfully synthesized by chemical conversion and the corrosion resistance of AZ91 samples with and without ceria coatings were evaluated by means of electrochemical corrosion in 3.5 wt.% NaCl solution. According to the parameters derived from the polarization date, the Icorr (the corrosion current density) values of the coated samples are smaller than that of bare one, indicating that the corrosion resistance of AZ91 alloys has been improved to some extent. The influence of fluoridated pretreatment, inter-layer heat treatment, sintering temperature and the layer of films on the performance of ceria coatings were also investigated. It was found that the inter-layer heat treatment has no influence on improving the anticorrosion resistance of AZ91 alloy. In comparison with the bare one, the Icorr of optimal sample is about 0.0219mA/cm2, which decreases by two orders of magnitude, indicating that the ceria coatings could significantly improve the corrosion resistance of AZ91 magnesium alloy.

Two-Step Anodization of AZ91 Magnesium Alloy

2005 ◽  
Vol 488-489 ◽  
pp. 653-656 ◽  
Author(s):  
Rong Fa Zhang ◽  
Da Yong Shan ◽  
En Hou Han
Keyword(s):  
Corrosion Resistance ◽  
Magnesium Alloy ◽  
Salt Spray ◽  
Az91 Magnesium Alloy ◽  
Anodic Coating ◽  
Excellent Corrosion Resistance ◽  
Long Time ◽  
Az91 Magnesium ◽  
Short Time ◽  
Salt Spray Testing

Among four AZ91 samples, two were once anodized and the others were twice anodized in two electrolytic baths. After twice anodization, two coatings coexist on the base metal. Surface morphology showed that for one of twice anodic coatings (sample 2), the second coating only existed on some places and sealed some pores of the first coating after short time on the second anodizing. However, for another twice anodic coating (namely sample 4), the second anodization spent very long time and the coating was thick and loose. Salt spray testing showed that sample 2 had the most excellent corrosion resistance and the reason is discussed.

Study on Micro-Arc Oxidation Behavior of AZ91 Magnesium Alloy in Aluminate Environmentally Friendly Electrolyte

2020 ◽  
Vol 1003 ◽  
pp. 67-75
Author(s):  
Xian Ming Chen ◽  
Ying Ying Fan
Keyword(s):  
Corrosion Resistance ◽  
Electron Microscope ◽  
Magnesium Alloy ◽  
Oxide Film ◽  
Oxidation Behavior ◽  
Salt Spray ◽  
Alkaline Electrolyte ◽  
Az91 Magnesium Alloy ◽  
Micro Arc Oxidation ◽  
Az91 Magnesium

In aluminate alkaline electrolyte the effect of aluminate on the microstructure and properties and the MAO(micro-arc oxidation) behavior of micro-arc oxide film of AZ91 magnesium alloy was studied. Transmission electron microscope(TEM), energy dispersive spectrum (EDS), X-ray diffraction(XRD), salt spray test and scanning electron microscope(SEM)were used to analyze and characterize the structure and properties of the film. The results show that the concentration of aluminate has an important effect on the tank voltage, corrosion resistance, surface morphology and phase structure of micro-arc oxidation film. The corrosion resistance and film quality of the film were increased first and then decreased, but the surface roughness decreased first and then increased with the increase of aluminate concentration from 5g/L to 30g/L. At our work, the concentration of 10g/L aluminate electrolyte is most favorable to the formation of micro-arc oxide film.

scholarly journals Effects Of Aluminum Sputtering On The Corrosion Resistance Of AZ91 Alloy

2015 ◽  
Vol 60 (2) ◽  
pp. 953-955 ◽  
Author(s):  
Y. Ishibashi ◽  
M. Nose ◽  
M. Hatakeyama ◽  
S. Sunada
Keyword(s):  
Heat Treatment ◽  
Corrosion Resistance ◽  
Magnesium Alloy ◽  
Az91 Alloy ◽  
Az91 Magnesium Alloy ◽  
Eds Analysis ◽  
Heat Treated ◽  
Film Forming ◽  
Az91 Magnesium ◽  
Aluminium Film

Abstract The corrosion resistance of a Magnesium alloy is low and needs to be improved. This research aimed at corrosion-resistance improvement by supatterd deposition aluminium film, which is formed on the surface of AZ91 Magnesium-alloy. Corrosion resistance performed polarization curve measurement, was evaluated in quest of the corrosion rate using the Tafel extrapolation method, and conducted surface observation and EDS analysis by SEM. Although corrosion resistance is not improved only by film forming because of defects in film, corrosion resistance is improved by heat treatment for 3 hours by 553K after sputtering. In the case of heat treated at 623K and 673K for 3 hours, magnesium diffuses through the alminium film and reached the surface of the film. Thus, heat treatment at high temperature degrade the corrosion resistance of the film. The optimization of heat treatment after sputtering is important in this method.

Corrosion behavior of biomedical AZ91 magnesium alloy in simulated body fluids

2007 ◽  
Vol 22 (7) ◽  
pp. 2004-2011 ◽  
Author(s):  
Yunchang Xin ◽  
Chenglong Liu ◽  
Xinmeng Zhang ◽  
Guoyi Tang ◽  
Xiubo Tian ◽  
...  
Keyword(s):  
Magnesium Alloy ◽  
Corrosion Behavior ◽  
Electrochemical Impedance ◽  
Visual Observation ◽  
Body Fluids ◽  
Open Circuit ◽  
Az91 Magnesium Alloy ◽  
Degradation Rates ◽  
Az91 Magnesium ◽  
Simulated Body Fluids

Fast degradation rates in the physiological environment constitute the main limitation for magnesium alloys used in biodegradable hard tissue implants. In this work, the corrosion behavior of AZ91 magnesium alloy in simulated body fluids (SBF) was systematically investigated to determine its performance in a physiological environment. The influence of the main constituent phases on the corrosion behavior was studied by in situ visual observation and scanning electron microscopy. Energy dispersive x-ray spectrometry and Fourier transfer infrared spectroscopy revealed that both calcium and magnesium phosphates are present in the corroded products besides magnesium oxide. Electrochemical methods including open circuit potential evolution and electrochemical impedance spectroscopy were used to investigate the mechanism. The corresponding electrode controlled processes and evolution of the corrosion products layer were discussed. The degradation rate after immersion in SBF for seven days was calculated from both the weight loss and hydrogen evolution methods.

Effect of Heat Treatment of AZ91 Magnesium Alloy on the Electroless Ni-P Deposition

2018 ◽  
Vol 1148 ◽  
pp. 122-127 ◽  
Author(s):  
Charu Singh ◽  
S.K. Tiwari ◽  
Raghuvir Singh
Keyword(s):  
Heat Treatment ◽  
Corrosion Resistance ◽  
Magnesium Alloy ◽  
Magnesium Alloys ◽  
Electrochemical Impedance ◽  
Cast Alloy ◽  
Az91 Magnesium Alloy ◽  
Heat Treated ◽  
Az91 Magnesium ◽  
Electroless Ni

Magnesium alloys are excellent choice for automobile, aerospace, and computer components owing to their light weight, unique physical and mechanical properties. However, poor corrosion resistance has restricted their applications in aggressive environments. The surface coating is one of the viable options to reduce the susceptibility of magnesium alloys to corrosion. The present study focuses on the effect of heat treatment of AZ91 magnesium alloy, for different durations at 400 °C, prior to electroless Ni-P deposition on corrosion resistance. The microstructure and elemental analysis of the heat-treated specimens are performed using SEM and EDS techniques respectively. It is observed that the duration of heat treatment has a significant effect on the surface morphology and microstructure of the alloy. The precipitates in the cast alloy (enriched with Mg and Al) fragmented and the transformed into a new Al and Zn rich phase, after 12 h heat treatment. The dissolution of precipitates, however, observed on heating further to 24 h and exhibited relatively a lesser corrosion current density. The dense electroless Ni-P deposition is formed on the alloy heat treated for 24 h. The corrosion behavior of the single Ni-P layer on the heat treated (for 12 h) and untreated alloy show a marked deterioration, as investigated by the anodic polarization and electrochemical impedance spectroscopy (EIS) techniques. Relatively a better corrosion performance is seen for the double-layer Ni-P deposition. The duplex layer coatings on the as cast and heat treated for 24 h at 400 °C substrates showed an improved corrosion resistance compared to that on the 12 h heat treated substrate.

Corrosion Behavior of AZ91/AZ91-0.4%Nd Alloys in 3.5wt.% NaCl

2013 ◽  
Vol 291-294 ◽  
pp. 699-702
Author(s):  
Ju Mei Zhang ◽  
Zhi Hu Wang ◽  
Hui Cai ◽  
Ming Zhu ◽  
Li Bin Niu
Keyword(s):  
Weight Loss ◽  
Corrosion Resistance ◽  
Magnesium Alloy ◽  
Corrosion Behavior ◽  
Immersion Test ◽  
Grain Refining ◽  
Az91 Magnesium Alloy ◽  
Weight Loss Method ◽  
Az91 Magnesium ◽  
Loss Method

The microstructure and corrosion behavior of commercial AZ91/AZ91-0.4%Nd alloys were investigated by OM, immersion test and weight-loss method. It was found that the number of Nd element in the AZ91 magnesium alloy has effect on the grain refining efficiency, the coarse β-Mg17Al12phase distributed along the grain boundaries transformed into granular, and the granular or acicular Al3Nd phase precipitated in matrix. The addition of Nd element significantly reduces the corrosion rate of AZ91-0.4%Nd magnesium alloy, as a result the corrosion resistance of alloy was improved obviously.

Microstructure and Corrosion Behavior of AZ91-0.4%Nd Magnesium Alloy

2013 ◽  
Vol 291-294 ◽  
pp. 2577-2580 ◽  
Author(s):  
Ju Mei Zhang ◽  
Zhi Hu Wang ◽  
Wan Chang Sun ◽  
Ming Zhu
Keyword(s):  
Corrosion Resistance ◽  
Magnesium Alloy ◽  
Corrosion Behavior ◽  
Immersion Test ◽  
Corrosion Products ◽  
Grain Refining ◽  
Az91 Magnesium Alloy ◽  
Refining Efficiency ◽  
Phase Precipitate ◽  
Az91 Magnesium

The corrosion behavior of AZ91-0.4%Nd alloys was investigated by immersion test in 3.5wt.% NaCl at 25°C. The phase compositions and microstructure of the AZ91-0.4%Nd alloy were characterized by XRD and OM, respectively. The results show that the number of Nd element in the AZ91 magnesium alloy has effect on the grain refining efficiency, and the granular or acicular Al3Nd phase precipitate in matrix.The corrosion products of the AZ91-0.4%Nd alloy mainly composed of Mg(OH)2and Al. The addition of Nd element significantly refine the microstructure and improve the compactness of corrosion products of AZ91-0.4%%Nd magnesium alloy, as a result the corrosion resistance of alloy was improved obviously.

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