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.

Formation and Properties of Zr/Ti Based Nano-Sized Non-Chromium Chemical Conversion Coating on AA 5083

2019 ◽  
Vol 19 (6) ◽  
pp. 3487-3494 ◽  
Author(s):  
Bin Liu ◽  
Yi Zhao ◽  
Liang Li ◽  
Yafei Feng ◽  
Zhigang Fang ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Acidic Solution ◽  
Salt Spray ◽  
Chemical Conversion ◽  
Conversion Coating ◽  
Dense Layer ◽  
Environment Friendly ◽  
Chemical Conversion Coating ◽  
Inhibitive Action ◽  
Nano Size

An environment-friendly non-chromium chemical conversion coating was obtained from fluozirconate/fluotitanate acidic solution for the corrosion protection of AA 5083. The surface morphology, composition, electrochemical behavior and corrosion resistance of this coating were investigated. The coating was found to be a homogeneous and dense layer consisting of nano-size particles, of which the major component was compound oxides consisted by Al, Mg, Zr, Ti, F and O. The results of electrochemical measurements, immersion and natural salt spray (NSS) tests demonstrated that the corrosion resistance of the AA 5083 H-116 was improved by the nano-sized non-chromium chemical conversion coating considerably, which was most attributed to the great inhibitive action on the anodic dissolution by acting as a protective barrier layer.

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.

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.

Rare Earth Conversion Coating of Magnesium Alloy AZ91D

2007 ◽  
Vol 546-549 ◽  
pp. 555-558
Author(s):  
Li Qun Bai ◽  
Di Li ◽  
Min Guo ◽  
Jing Xin
Keyword(s):  
Corrosion Resistance ◽  
Rare Earth ◽  
Magnesium Alloy ◽  
Electrochemical Behavior ◽  
Chemical Conversion ◽  
Conversion Coating ◽  
Alloy Az91d ◽  
Chemical Conversion Coating ◽  
Chloride Environment ◽  
Surface Morphologies

Rare earth chemical conversion coating of Mg alloys was studied. Corrosion and electrochemical behavior in chloride environment were investigated with tests of evolution of hydrogen and electrochemical measurements. The surface morphologies and composition of rare earth conversion coating were studied through SEM, EDAX and XPS. The results showed that rare earth conversion coatings could improve corrosion resistance and their corrosion resistance was comparable with that of chromate coatings (HB/Z5078278). This result was further proved by Polarization and EIS.

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