Corrosion Resistance Enhancement of AZ91D Magnesium Alloy by Electroless Ni-Co-P Coating and Ni-Co-P-SiO2 Nanocomposite

2014 ◽  
Vol 23 (11) ◽  
pp. 4109-4121 ◽  
Author(s):  
Davod Seifzadeh ◽  
Amin Rahimzadeh Hollagh
Keyword(s):  
Corrosion Resistance ◽  
Magnesium Alloy ◽  
Az91d Magnesium Alloy ◽  
Electroless Ni

Improvement of Adhesion Strength of Electroless Nickel Coating on AZ91D by Anodized Oxide Interlayer

2012 ◽  
Vol 509 ◽  
pp. 90-95
Author(s):  
Hsien Ta Hsu ◽  
Tsong Jen Yang
Keyword(s):  
Corrosion Resistance ◽  
Magnesium Alloy ◽  
Adhesion Strength ◽  
Electroless Nickel ◽  
Anodic Oxide ◽  
Duplex Coating ◽  
Az91d Magnesium Alloy ◽  
Alloy Az91d ◽  
Surface Morphologies ◽  
Electroless Ni

Nickel-oxide duplex coatings were successfully deposited on magnesium alloy (AZ91D) by anodizing and electroless nickel-phosphorus plating processes. The anodizing interlayer was used to increase the adhesion strength of Ni-P layer. The electroless Ni-P coating enhances the corrosion resistance of the anodic oxide layer. Specimen of AZ91D magnesium alloy was polished firstly. The anodizing process was preceded in alkaline anodizing solution at 24 °C, and the bath voltage maintained at 70 volts for 2 hours. Successive electroless Ni-P plating was used to achieve the sandwich structure. The surface morphologies of the coatings were observed by field-emission scanning electron microscopy (FE-SEM). The adhesion strength was measured by pull-off tester. The electrochemical behavior of coatings with corrosion resistance in 3.5 wt.% NaCl solution was evaluated by potential polarization curve. The experimental results showed that the adhesion strength of directly deposited coating and duplex coating were 115.4 kgf/cm2 and 142.2 kgf/cm2, respectively. The adhesion strength of coatings on AZ91D magnesium alloy was improved by the synergistic effect between anodized magnesium oxide and Ni-P layer in duplex coating.

Electroless Ni–Sn–P coating on AZ91D magnesium alloy and its corrosion resistance

2008 ◽  
Vol 202 (12) ◽  
pp. 2570-2576 ◽  
Author(s):  
W.X. Zhang ◽  
Z.H. Jiang ◽  
G.Y. Li ◽  
Q. Jiang ◽  
J.S. Lian
Keyword(s):  
Corrosion Resistance ◽  
Magnesium Alloy ◽  
Az91d Magnesium Alloy ◽  
Electroless Ni

A Preliminary Study of Anodization and Electroless Ni–P Plating on AZ80 Magnesium Alloy

2011 ◽  
Vol 299-300 ◽  
pp. 663-666 ◽  
Author(s):  
Ping Shi ◽  
Xue Dong Han
Keyword(s):  
Corrosion Resistance ◽  
Magnesium Alloy ◽  
Weight Ratio ◽  
High Strength ◽  
Surface Modifications ◽  
Atomic Ratio ◽  
Az80 Magnesium Alloy ◽  
Micro Arc Oxidation ◽  
Preliminary Study ◽  
Electroless Ni

Magnesium alloys are being used as structural components in industry because of their high strength to weight ratio. But their high electrochemical activity and poor corrosion resistance limited their applications. Therefore, surface modifications are needed for protection purpose. This paper studied the anodic micro-arc oxidation and electroless Ni-P plating surface modifications on AZ80 magnesium alloy. The SEM, XRD and EDS were used to characterize the surface coating. It shows that a micro-porous MgO layer with the pores size 5 – 20 μm was fabricated on the bare magnesium alloy. The nodule Ni-P deposition could be prepared on the out layer of MgO with Ni/P atomic ratio being 1.4. The pores in MgO layer could be sealed by the following Ni-P deposition. Therefore the corrosion resistance of the magnesium alloy could be further improved.

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