IMPROVEMENT OF CORROSION RESISTANCE OF AZ91D MAGNESIUM ALLOY BY LANTHANUM-BASED CONVERSION COATING

2013 ◽  
Vol 21 (1) ◽  
pp. 53-61
Author(s):  
M. Z. M. Zamzuri ◽  
◽  
N. F. W. M. Sidik ◽  
M. N. B. Derman ◽  
S. Norbahiyah ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Magnesium Alloy ◽  
Conversion Coating ◽  
Az91d Magnesium Alloy

Effect of Alkaline Phosphate-Permanganate Conversion Coating on the Corrosion Resistance of AZ91D Magnesium Alloy

2014 ◽  
Vol 974 ◽  
pp. 43-49 ◽  
Author(s):  
Young Min Byoun ◽  
Jin Hwan Jeong ◽  
Jong Kyu Park ◽  
Sun Kyo Seo ◽  
Chi Hwan Lee
Keyword(s):  
Corrosion Resistance ◽  
Magnesium Alloy ◽  
Coating Layer ◽  
Salt Spray ◽  
Xrd Analysis ◽  
Conversion Coating ◽  
Surface And Interface ◽  
Az91d Magnesium Alloy ◽  
Coating Layers ◽  
Alkaline Phosphate

Alkaline phosphate-permanganate conversion coating, chrome-free conversion coating was studied for corrosion resistance of AZ91D magnesium alloy. Also, conventional acid phosphate -permanganate conversion coating was studied for comparison. Analysis and morphology observation for conversion coating layers was investigated in details by using SEM-EDS, XRD. SEM observation showed that a lot of cracks in surface and interface between conversion coating layer and AZ91D magnesium alloy substrate was observed in acid conversion coating, whereas cracks was not almost observed in alkaline conversion coating layer. SEM-EDS and XRD analysis showed that the main elements of both alkaline and acid conversion coating were Mg, O, K, P and Mn. It was found that both conversion coating layers was consisted of MgO, Mg (OH)2and MnO2. Salt spray test showed that the alkaline conversion coating have a good corrosion resistance compared with acid conversion coating.

EIS Study of Molybdate Conversion Coatings Formed on AZ91D Magnesium Alloy

2011 ◽  
Vol 189-193 ◽  
pp. 279-285
Author(s):  
Li Ping Wu ◽  
Zhong Dong Yang
Keyword(s):  
Corrosion Resistance ◽  
Charge Transfer ◽  
Magnesium Alloy ◽  
Charge Transfer Resistance ◽  
Conversion Coating ◽  
Conversion Coatings ◽  
Bath Composition ◽  
Optimum Conditions ◽  
Transfer Resistance ◽  
Az91d Magnesium Alloy

An environmentally friendly molybdate conversion coating based surface treatment was developed for AZ91D magnesium alloy. The EIS technique was employed to study the effects of the conversion bath composition and temperature on the corrosion protection performance of molybdate conversion coatings on AZ91D magnesium alloys. The optimum conditions under which obtained conversion coatings showed the best corrosion resistance were determined. The Nyquist results showed that the value of charge transfer resistance increased by 22.5 times for the sample treated in the optimized molybdate conversion bath.

Effect of NaVO3 Concentration on Corrosion Resistance of Conversion Coating on AZ91D Magnesium Alloy

2012 ◽  
Vol 576 ◽  
pp. 438-441 ◽  
Author(s):  
N.F.W.M. Sidik ◽  
M.Z.M. Zamzuri ◽  
M. Mat Salleh ◽  
Khairul Azwan Ismail
Keyword(s):  
Corrosion Resistance ◽  
Magnesium Alloy ◽  
Oxide Films ◽  
Chemical Conversion ◽  
Immersion Test ◽  
Optical Microscope ◽  
Conversion Coating ◽  
Energy Dispersive Analysis ◽  
Az91d Magnesium Alloy ◽  
Superior Corrosion Resistance

Anticorrosive oxide films were successfully prepared on AZ91D magnesium alloy by chemical conversion coating in La (NO3)3 electrolytes with and without NaVO3. The morphologies and chemical composition were characterized by optical microscope, scanning electron microscope (SEM) and energy dispersive analysis (EDX). The corrosion resistances of the oxide films were evaluated by salt immersion test. The result showed that the oxide film formed in electrolyte with NaVO3 is successful in providing superior corrosion resistance for AZ91D magnesium alloy.

Effect of Chrome-Free Chemical Conversion Coating on Corrosion Behavior of Magnesium Alloy AZ91D

2006 ◽  
Vol 15-17 ◽  
pp. 473-478
Author(s):  
Li Qun Bai ◽  
Di Li ◽  
Bao Lan Guo ◽  
Min Guo
Keyword(s):  
Corrosion Resistance ◽  
Magnesium Alloy ◽  
Salt Spray ◽  
Chemical Conversion ◽  
Electrochemical Measurement ◽  
Conversion Coating ◽  
Hydrogen Gas ◽  
Az91d Magnesium Alloy ◽  
One Step ◽  
Chemical Conversion Coating

The different chrome-free chemical conversion coatings were prepared on AZ91D magnesium alloy and SEM was used to observe the surface. The corrosion behaviors of die-casting AZ91D magnesium alloy with different coating in chloride environment were investigated by hydrogen gas evolution in immersion test, salt spray test and electrochemical measurement. The results showed that the corrosion resistance of magnesium alloy treated with two-step chemical conversion and sealing was the highest and was comparable with that of chromating, and followed by two-step chemical conversion treatment without sealing. The one-step chemical conversion treatment had the lowest corrosion resistance. Polarization and EIS characteristics in 5% NaCl solution depended on the type of surface treatment and correlated well with the order of corrosion resistance. Contrasted with one-step chemical conversion coating, the coating of two-step chemical conversion with sealing on magnesium alloy had more excellent corrosion resistance because the |Z| increased, the corrosion area was decreased and the time of the first pitting occurrence was prolonged. It is expected that this experiment can provide a foundation for designing more super chemical conversion coating to replacing the chromate conversion.

Effect of Niobium Film on Corrosion Resistance of AZ91D Magnesium Alloy

2012 ◽  
Vol 525-526 ◽  
pp. 9-12 ◽  
Author(s):  
Er Bao Liu ◽  
Xiu Fang Cui ◽  
Guo Jin ◽  
Qing Fen Li ◽  
Tian Min Shao
Keyword(s):  
Corrosion Resistance ◽  
Elastic Modulus ◽  
Magnesium Alloy ◽  
Substrate Temperature ◽  
Phase Structure ◽  
Film Deposition ◽  
Negative Bias ◽  
Az91d Magnesium Alloy ◽  
Atomic Force ◽  
Deposition Parameters

The niobium film is prepared by magnetron sputtering on the surface of the AZ91D magnesium alloy. The morphology, phase structure, roughness, nanohardness and elastic modulus of the niobium films were studied by filed emission scanning electron microscope, X-ray diffraction, atomic force microscope and nanoindentation respectively. The influences of film deposition parameters, such as substrate temperature, negative bias and power on the properties of films were investigated. The corrosion resistance of niobium films on magnesium alloy was investigated by electrochemical system. Results show that the microstructure, phase structure, roughness, nanohardness and elastic modulus of the niobium films are determined by power, negative bias and substrate temperature. And the corrosion resistance of magnesium alloy improved obviously when coated with the niobium films.

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