A Novel Electroless Ni-P Deposition on AZ91D Magnesium Alloy

2010 ◽  
Vol 154-155 ◽  
pp. 1330-1335
Author(s):  
Li Ping Wu ◽  
Zhong Dong Yang ◽  
Jing Jing Zhao ◽  
Yong Ping Xie
Keyword(s):  
Magnesium Alloy ◽  
Electrochemical Impedance ◽  
Electroless Nickel ◽  
Deposition Process ◽  
Chemical Compositions ◽  
Good Adhesion ◽  
Plating Bath ◽  
Az91d Magnesium Alloy ◽  
Structure Morphology ◽  
Electroless Ni

Currently, most of electroless nickel phosphorus plating on magnesium alloys has following disadvantages. First, it has been suffering from corrosion issues caused by acidic electroless bath. Second, in order to increase the strength of Ni-P coatings to the Mg substrate, the pretreatments for electroless Ni-P employ hydrofluoric acid (HF) and hexavalent chromium (Cr6+) which can cause pollution and health problems . In this paper, we developed HF-free and alkaline electroless Ni-P deposition process on AZ91D magnesium alloy which avoids the use of SO42- and Cl- ions in the electroless plating bath, thus leading to good adhesion and corrosion resistance of electroless Ni-P coating on magnesium alloy. XRD, SEM, EDS techniques were used to study the structure, morphology, and chemical compositions of the conversion coating and Ni-P coating, respectively. Polarization measurements indicated that the corrosion rate of Ni-P coated Mg was six times lower than that of bare Mg. Electrochemical impedance spectroscopy (EIS) also showed that the Ni-P coating could effectively protect Mg alloy from corrosion.

THE CORROSION BEHAVIOR OF ELECTROLESS Ni-P-SiC NANO-COMPOSITE COATING

2008 ◽  
Vol 22 (18n19) ◽  
pp. 3031-3036 ◽  
Author(s):  
FARYAD BIGDELI ◽  
SAEED REZA ALLAHKARAM
Keyword(s):  
Corrosion Resistance ◽  
Electrochemical Impedance ◽  
Composite Coatings ◽  
Electroless Nickel ◽  
Energy Dispersive Spectrum ◽  
X Ray Diffraction ◽  
Plating Bath ◽  
New Class ◽  
Nano Composite Coating ◽  
Electroless Ni

Composite coatings constitute a new class of materials which are mostly used for mechanical and tribological applications. The corrosion resistance of these composite coatings, however, has not been systematically studied and compared. In this study, electroless Ni – P composite coatings are formed on St 37 steel through the addition of nano-scale SiC particles to the plating bath. This work aimed to investigate the corrosion characteristics of electroless nickel composite coatings using electrochemical measurements which include polarization and electrochemical impedance spectroscopy tests. The morphology and structure of the composite coatings were studied by scanning electron microscopy (SEM), energy dispersive spectrum (EDS) and X-ray diffraction (XRD). The results showed that both electroless nickel and electroless nickel composite coatings demonstrated significant improvement of corrosion resistance in salty atmosphere.

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.

Optimizing of Pretreatment Process of Electroless Ni-P Plating on AZ91D Substrate

2011 ◽  
Vol 239-242 ◽  
pp. 1915-1918
Author(s):  
Guan Jun Liu ◽  
Zhou Yu ◽  
Li Jie Ma ◽  
Jun Cao
Keyword(s):  
Electron Microscope ◽  
Magnesium Alloy ◽  
Orthogonal Test ◽  
Bending Test ◽  
Az91d Magnesium Alloy ◽  
Plating Solution ◽  
Electroless Ni ◽  
Good Coating ◽  
Alternating Bending ◽  
Scanning Electron

In order to improve and simplify the process of electroless Ni-P plating on AZ91D magnesium alloy substrate, pretreatment process and deposite time were optimized by orthogonal test, the plating morphology were analysed using Quanta 200 type scanning electron microscope. The bond between the plating and aluminum substrate were evaluated using method of water quenching and alternating bending test. The results show that good coating can be obtained on AZ91D substrate under the condition of the acid electroless Ni-P plating solution with pickling time of 40-50s, activated time of 10 min. And the good bond between the coating and AZ91D substrate was obtained.

HIGH CORROSION RESISTANCE OF NI-P/NANO-SIO2 ELECTROLESS COMPOSITE COATINGS

2012 ◽  
Vol 05 ◽  
pp. 810-816 ◽  
Author(s):  
S.R. Allahkaram ◽  
T. Rabizadeh
Keyword(s):  
Corrosion Resistance ◽  
Electrochemical Impedance ◽  
Composite Coatings ◽  
Carbon Steels ◽  
Nano Particles ◽  
Chemical Compositions ◽  
High Corrosion Resistance ◽  
Coating Type ◽  
Corrosion Behaviors ◽  
Electroless Ni

The process of electroless plating Ni - P and Ni - P /nano- SiO 2 on API-5L X65 carbon steels was improved. The Ni - P /nano- SiO 2 composite coatings were prepared from the bathes containing different concentrations of nano- SiO 2 particles. The coatings surface and morphologies were observed via scanning electron microscopy (SEM). The chemical compositions were analyzed by EDAX. The corrosion behaviors were evaluated by electrochemical impedance spectroscopy tests. The experimental results indicated that SiO 2 nano-particles co-deposited but some agglomeration occurred. Micro-hardness of electroless Ni - P - SiO 2 composite coatings increased due to the existence of nano-particles. Corrosion tests showed that both electroless Ni - P and Ni - P /nano- SiO 2 composite coatings demonstrated significant improvement of corrosion resistance of substrate in salty atmosphere and latter coating type appeared to offer a better corrosion protection.

Deposition Mechanism Study of a Novel Electroless Nickel Plating Technique on AZ91D Magnesium Alloy

2011 ◽  
Vol 393-395 ◽  
pp. 40-43
Author(s):  
Jian Gang Qian ◽  
Tian Zhao
Keyword(s):  
Magnesium Alloy ◽  
Electroless Nickel ◽  
Nickel Layer ◽  
High Catalytic Activity ◽  
Electroless Nickel Plating ◽  
Nickel Plating ◽  
Mechanism Study ◽  
Deposition Mechanism ◽  
Az91d Magnesium Alloy ◽  
Initial Deposition

A novel direct electroless nickel plating method was developed for the AZ91D magnesium alloy. The electroless nickel initial deposition morphology was analyzed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The initial deposition characteristics of the coating and the deposition mechanism of the nickel layer are discussed. The results show that after activation, an uneven scaly-activated membrane was formed on the AZ91D magnesium alloy surface. The weakest part of the activated membrane dissolved first, where small Ni particles deposited initially. These deposited Ni particles had high catalytic activity and they were involved in the catalytic reduction reaction of hypophosphite, from which P was precipitated. As the plating proceeded, the number of the deposited Ni particles gradually increased in a three-dimensional manner and the surface was gradually covered by the growing cellular particles. A compact pore-free nickel-plated film was finally formed.

Electroless Ni–P deposition plus zinc phosphate coating on AZ91D magnesium alloy

2006 ◽  
Vol 200 (20-21) ◽  
pp. 5956-5962 ◽  
Author(s):  
J.S. Lian ◽  
G.Y. Li ◽  
L.Y. Niu ◽  
C.D. Gu ◽  
Z.H. Jiang ◽  
...  
Keyword(s):  
Magnesium Alloy ◽  
Zinc Phosphate ◽  
Phosphate Coating ◽  
Az91d Magnesium Alloy ◽  
Electroless Ni

scholarly journals Corrosion Resistance of Electroless Ni-Cu-P Ternary Alloy Coatings in Acidic and Neutral Corrosive Mediums

2010 ◽  
Vol 2010 ◽  
pp. 1-9 ◽  
Author(s):  
Mbouillé Cissé ◽  
Mohamed Abouchane ◽  
Tayeb Anik ◽  
Karima Himm ◽  
Rida Allah Belakhmima ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Electrochemical Impedance ◽  
Steel Substrate ◽  
Corrosion Mechanism ◽  
X Ray Diffraction ◽  
Plating Bath ◽  
Edx Analysis ◽  
Tafel Polarization ◽  
Marginal Improvement ◽  
Electroless Ni

Electroless Ni-Cu-P alloy coatings were deposited on the ordinary steel substrate in an acidic hypophosphite-type plating bath. These coatings were characterized by a scanning electron microscope (SEM) and an X-ray diffraction. The micrograph shows that coating presents a nodular aspect and is relatively homogeneous and very smooth. The EDX analysis shows that the coating contains 12 wt.% of phosphorus element with a predominance of nickel element. In addition, the anticorrosion properties of the Ni-Cu-P coatings in 1 M HCl, 1 M H2SO4, and 3% NaCl solutions were investigated using Tafel polarization curves, electrochemical impedance spectroscopy, and SEM/EDX analysis. The result showed a marginal improvement in corrosion resistance in 3% NaCl solution compared to acidic medium. It also showed that the corrosion mechanism depends on the nature of the solution.

Direct electroless nickel–boron plating on AZ91D magnesium alloy

2012 ◽  
Vol 206 (17) ◽  
pp. 3676-3685 ◽  
Author(s):  
Z.C. Wang ◽  
F. Jia ◽  
L. Yu ◽  
Z.B. Qi ◽  
Y. Tang ◽  
...  
Keyword(s):  
Magnesium Alloy ◽  
Electroless Nickel ◽  
Az91d Magnesium Alloy
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