Influence of pH values on electroless Ni-P-SiC plating on AZ91D magnesium alloy

A dense electroless plating was obtained through the process of chemical Ni-P-γAl2O3 composite plating by ultrasonic wave. The influence of pH on deposition rate, microstructure, coating thickness and microhardness of the composite plating was studied. The deposition rates of the coating is the fastest at pH value of 7,which is 17.9×10-5g/cm2/min.The microstructure of the Ni-P-γAl2O3 coatings were analyzed by scanning electron microscopy (SEM). The results indicate that the influence of pH value on magnesium alloy is very large.And the composite coating obtained at pH value of 7 possesses optimal integrated properties, which shows uniform and compact. The plating obtained at pH value of 7 is the thicknest.

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

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.239-242.1915 ◽

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.

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

Surface and Coatings Technology ◽

10.1016/j.surfcoat.2005.09.007 ◽

2006 ◽

Vol 200 (20-21) ◽

pp. 5956-5962 ◽

Cited By ~ 91

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

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Preparation and corrosion resistance of electroless Ni-P/SiC functionally gradient coatings on AZ91D magnesium alloy

Applied Surface Science ◽

10.1016/j.apsusc.2013.09.079 ◽

2013 ◽

Vol 286 ◽

pp. 319-327 ◽

Cited By ~ 51

Author(s):

Hui-Long Wang ◽

Ling-Yun Liu ◽

Yong Dou ◽

Wen-Zhu Zhang ◽

Wen-Feng Jiang

Keyword(s):

Corrosion Resistance ◽

Magnesium Alloy ◽

Az91d Magnesium Alloy ◽

Functionally Gradient ◽

Gradient Coatings ◽

Electroless Ni

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A Novel Electroless Ni-P Deposition on AZ91D Magnesium Alloy

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.154-155.1330 ◽

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.

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