scholarly journals A New Route for Direct Electroless Ni-P Plating on Magnesium Alloys

2017 ◽  
Vol 33 (2) ◽  
Author(s):  
Bùi Xuân Vương
Keyword(s):  
Corrosion Resistance ◽  
Magnesium Alloys ◽  
Substrate Surface ◽  
Nickel Sulfate ◽  
Plating Bath ◽  
High Adhesion ◽  
Pickling Solution ◽  
Salt Component ◽  
Coarse Surface ◽  
Electroless Ni

This report describes a new route for direct electroless Ni-P plating on magnesium alloys using nickel sulfate as the main salt component. The surface morphology, chemical composition and corrosion resistance of coatings were determined using SEM, EDX and electrochemical polarization techniques. Ni-P coatings with good corrosion resistance and high adhesion were obtained using this route and improved pretreatments. A mixture of H3PO4 and HNO3 was used as a pickling solution for Mg substrate pretreatment. A coarse surface was produced via the developed pickling procedure. A mechanical occlusive force is believed to exist between the coatings and the substrates. Twice activations, K4P2O7 and NH4HF2 as activation components, respectively, were applied for the pretreatment of magnesium alloy plating. An optimal F/O ratio on the Mg substrate surface was obtained by this pretreatment method. The activation film has insoluble partial fluorides which can depress the active points on substrate surface against the reaction of Mg with Ni2+ and H+ in the plating bath. A highly stable bath with pH 5 buffer was identified. The advantages of the developed process include chromium-free, low fluoride, and high bath stability. It is applicable for the production of motorcycle part plating.  

scholarly journals Optimization of the Corrosion Resistance of Electroless Ni–W–P Coatings on Magnesium Alloys by the Response Surface Methodology

Coatings ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 18
Author(s):  
Bin Liu ◽  
Qing Zhang ◽  
Yang Li ◽  
Yuebo Yang ◽  
Tao Zhang ◽  
...  
Keyword(s):  
Response Surface Methodology ◽  
Corrosion Resistance ◽  
Response Surface ◽  
Magnesium Alloys ◽  
Sodium Tungstate ◽  
Nickel Sulfate ◽  
Bath Temperature ◽  
Sodium Hypophosphite ◽  
Technological Parameters ◽  
Electroless Ni

Plating processes greatly affect the corrosion resistance of electroless Ni–W–P coatings on magnesium alloys. In the present research, the corrosion resistance of electroless Ni–W–P alloy-coated AZ91D magnesium alloy was optimized by the response surface methodology. The optimum technological parameters of the plating process were determined by establishing a quadratic regression model, and the influence of these variables and their interactions on the corrosion resistance of the coating was analyzed. The optimum technological parameters of the electroless plating process were nickel sulfate concentration = 20 g/L, sodium tungstate concentration = 15 g/L, sodium hypophosphite concentration = 30 g/L, bath temperature = 60 °C, and bath pH = 9.3. Under these conditions, the coating had the best corrosion resistance. Among the aforementioned five variables, sodium tungstate concentration had the most significant influence on the corrosion resistance of the coating. Different degrees of interactions among the variables greatly affected the corrosion resistance of the coating.

A New Pre-Treatment with Phosphoric Acid and Hydrofluoric Acid of Electroless Ni-P Plating on Mg Alloy

2015 ◽  
Vol 729 ◽  
pp. 21-26
Author(s):  
Zhi Hui Xie ◽  
Jun Li Zhou ◽  
Shu Rong Xiang ◽  
Fang Chen
Keyword(s):  
Corrosion Current ◽  
Treatment Method ◽  
Mg Alloy ◽  
Cross Sectional ◽  
Plating Bath ◽  
Pickling Solution ◽  
Before And After ◽  
The Matrix ◽  
Pre Treatment ◽  
Electroless Ni

In order to develop a chromium-free pre-treatment method for electroless Ni-P (ENP) plating on magnesium alloy from an acidic plating bath, several various pickling and activation processes were studied in the present work. The surface morphologies of the matrix before and after etching or activation as well as the surface and cross sectional appearance of the Ni-P coatings were observed by scanning electronic microscope (SEM), while the elemental compositions were detected by energy dispersive X-ray spectroscopy (EDS). Those surface characterizations along with the scribe and grid testing results showed that the coatings obtained from etching only in H3PO4 solution display poor adhesion due to the existance of an interlayer between the matrix and the coatings. When fluoride was added into the pickling solution, the adhesion of the Ni-P coatings was also unsatisfactory because of the bad mechanical interlocking. By comparison, the Ni-P coatings obtained from pickling in 400 cm3·dm−3 H3PO4 solution followed by 10 cm3·dm−3 HF activation exhibit good characteristics in both adhesion and anti corrosion. The polarization test in 3.5wt.% NaCl aqueous solution showed that the corrosion potential (Ecorr) and corrosion current density (Icorr) of the new achieved coatings increases positively from −1.65 V to −0.87 V and decreases remarkably from 2.09 mA⋅cm−2 to 3.58 μA⋅cm−2, respectively (both compared with the bare Mg alloy).

Recent Studies on Coating of some Magnesium Alloys; Anodizing, Electroless Coating and Hot Press Cladding

2012 ◽  
Vol 533 ◽  
pp. 167-181
Author(s):  
Nahed El Mahallawy ◽  
Mohamed Harhash
Keyword(s):  
Corrosion Resistance ◽  
Magnesium Alloys ◽  
Deposition Time ◽  
Anodic Film ◽  
Hot Press ◽  
Bond Quality ◽  
The Third ◽  
Environmental Friendly ◽  
Pre Treatment ◽  
Electroless Ni

In the present study, coating of some magnesium alloys including AZ31 and AZ91 were studied using different techniques namely anodizing, electroless and hot press cladding. AZ91 alloy was coated using anodizing process using three types of environmental friendly electrolytes; the first based on sodium silicate, the second based on sodium hydroxide-boric acid-borax and the third on sodium silicate-potassium hydroxide-sodium carbonate-sodium tetra borate. Characterization of the anodizing layer was achieved by determination of surface morphology, microstructure, phase analysis, coat thickness, adhesion and corrosion resistance. It was found that the anodic film thickness increases with increasing the current density, anodizing voltage and deposition time until the deposition stops due to the formation of a thick anodic film. The range of the anodic film thickness is 28 42 µm.Optimization of the anodizing conditions - current density and deposition time was determined for each electrolyte. A corrosion efficiency ranging from 94% to 97% was reached; the highest value corresponding to the third electrolyte. Another study is the electroless Ni plating technique with zinc pre-treatment applied on several magnesium alloys and the effect of pre-treatment and post heat treatment on the coat characteristics. The surface morphology, surface roughness, thickness of the layer, EDX analysis, adhesion, hardness and corrosion resistance are covered in this part. The electroless layer thickness is about 6 µm. The results showed good bond quality of the coat maintaining good corrosion behaviour of electroless Ni-P based on potentiodynamic polarization tests in chloride solution where it was improved after heat treatment process. On the other hand, AZ31 was covered by a commercial pure aluminum sheet by hot pressing. The influence of the applied pressure, holding time and temperature on the bond characteristics was studied. The experimental investigation has revealed a good bond quality due to the effective mutual diffusion of Mg and Al. The phase analysis resulted in the formation of two equilibrium phases namely; Mg17Al12and Mg2Al3. The corrosion resistance of AZ31 is enhanced as a results of this process by 98.6%. Further points will be covered.Keywords: Magnesium alloys; Coating; Anodizing; Electroless; Hot press cladding; environmental friendly electrolytes; corrosion

Fast Electroless Ni-P Coating on AM60 Magnesium Alloy at Low Bath Temperature

2011 ◽  
Vol 418-420 ◽  
pp. 756-759 ◽  
Author(s):  
Guo Bing Mao
Keyword(s):  
Growth Rate ◽  
Corrosion Resistance ◽  
Magnesium Alloy ◽  
Magnesium Alloys ◽  
Electroless Plating ◽  
Corrosion Test ◽  
Bath Temperature ◽  
Test Results ◽  
Electroless Ni

The Ni-P coatings were deposited on AM60 magnesium alloy by electroless plating process without or with accelerators. Without accelerators, the deposition rate is slow and required high bath temperature to obtain compact coating. There have many defects on the surface of the Ni-P coatings which deposited at high bath temperature. The composite accelerators were introduced into the bath for improving the growth rate and the quality of the Ni-P coating. Uniform, with no pores or cracks, “cauliflower-like” structure and complete Ni-P coatings were deposited only taken 20 min with additives at low bath temperature. The XRD result indicates that the structure of the Ni-P coating is amorphous nickel. The corrosion test results indicated that the corrosion resistance of this coated AM60 magnesium alloys increases distinctly as compared to bare alloys.

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.

Electroless Ni-P-Cg(Graphite)-SiC Composite Coating on Cast AlSi Alloy

2013 ◽  
Vol 795 ◽  
pp. 540-544
Author(s):  
M.M. Mohtar ◽  
Z.M. Ripin ◽  
Z.A. Ahmad
Keyword(s):  
Film Thickness ◽  
Composite Coating ◽  
Substrate Surface ◽  
Bath Temperature ◽  
Coating Film ◽  
Chemical Concentration ◽  
Plating Bath ◽  
Alsi Alloy ◽  
Ph Level ◽  
Electroless Ni

The study presents the electroless N-P-Cg-SiC composite coating on cast AlSi (ADC12) alloy where the bath temperature is maintained at 90°C, pH level is controlled between 4.5 to 5.0 and stirred at 450 rpm with mechanical stirrer to avoid particles sedimentation. The increase of the coating film thickness is very insignificant after one hour of coating duration. This outcome is supposed to be due to inconsistent chemical concentration in the plating bath after this period. The nominal coating thickness of 39 μm is achieved after the substrate is immersed for 1 hour in four consecutive plating baths, respectively. The coating film is also successfully adhered to the substrate surface with the SiC and Cgparticles are homogenously distributed.

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.

Effect of Bath Compositions on the Properties of Electroless Ni-Cu-P Alloys on Aluminum

2011 ◽  
Vol 117-119 ◽  
pp. 1276-1279 ◽  
Author(s):  
Xi Ran Wang ◽  
Xin Gang Hu ◽  
Wei Yuan Li
Keyword(s):  
Corrosion Resistance ◽  
Electroless Plating ◽  
Sodium Citrate ◽  
Nickel Sulfate ◽  
Sodium Hypophosphite ◽  
Micro Hardness ◽  
X Ray ◽  
Plating Method ◽  
The Matrix ◽  
Electroless Ni

In this work, the electroless plating Ni-Cu-P on aluminium is obtained successfully by direct Ni-Cu-P plating method. The effect of bath compositions on the electroless plating rate and the properties of the electroless Ni-Cu-P deposits was studied by orthogonal test. The corrosion resistance, hardness, surface morphology and components of the coating were studied by using electrochemical workstation, digital micro-hardness SEM and EDS. The optimum bath formula obtained is 0.6g/L copper sulfate, 30g/L nickel sulfate, 35g/L sodium citrate, 25 g/L sodium hypophosphite, 20g/L acetic anhydride and right amount of self-made additive. The deposition rate, hardness and corrosion resistance are all good. The adhesion between the deposits and the matrix is better. The deposits is smooth and uniformity, smooth by SEM. The deposit contains Ni 78.90%, Cu 8.65%, P 12.46% by the analyses of energy disperse X-ray.

Effect of Heat Treatment of AZ91 Magnesium Alloy on the Electroless Ni-P Deposition

2018 ◽  
Vol 1148 ◽  
pp. 122-127 ◽  
Author(s):  
Charu Singh ◽  
S.K. Tiwari ◽  
Raghuvir Singh
Keyword(s):  
Heat Treatment ◽  
Corrosion Resistance ◽  
Magnesium Alloy ◽  
Magnesium Alloys ◽  
Electrochemical Impedance ◽  
Cast Alloy ◽  
Az91 Magnesium Alloy ◽  
Heat Treated ◽  
Az91 Magnesium ◽  
Electroless Ni

Magnesium alloys are excellent choice for automobile, aerospace, and computer components owing to their light weight, unique physical and mechanical properties. However, poor corrosion resistance has restricted their applications in aggressive environments. The surface coating is one of the viable options to reduce the susceptibility of magnesium alloys to corrosion. The present study focuses on the effect of heat treatment of AZ91 magnesium alloy, for different durations at 400 °C, prior to electroless Ni-P deposition on corrosion resistance. The microstructure and elemental analysis of the heat-treated specimens are performed using SEM and EDS techniques respectively. It is observed that the duration of heat treatment has a significant effect on the surface morphology and microstructure of the alloy. The precipitates in the cast alloy (enriched with Mg and Al) fragmented and the transformed into a new Al and Zn rich phase, after 12 h heat treatment. The dissolution of precipitates, however, observed on heating further to 24 h and exhibited relatively a lesser corrosion current density. The dense electroless Ni-P deposition is formed on the alloy heat treated for 24 h. The corrosion behavior of the single Ni-P layer on the heat treated (for 12 h) and untreated alloy show a marked deterioration, as investigated by the anodic polarization and electrochemical impedance spectroscopy (EIS) techniques. Relatively a better corrosion performance is seen for the double-layer Ni-P deposition. The duplex layer coatings on the as cast and heat treated for 24 h at 400 °C substrates showed an improved corrosion resistance compared to that on the 12 h heat treated substrate.

Electrochemical Impedance Behavior of Various Composition Quaternary Ni Alloy in 3.5 Wt% NaCl

2015 ◽  
Vol 761 ◽  
pp. 407-411 ◽  
Author(s):  
Muhammad Zaimi ◽  
Mohd Asyadi Azam ◽  
Azizul Helmi Sofian ◽  
Kazuhiko Noda
Keyword(s):  
Corrosion Resistance ◽  
Corrosion Behavior ◽  
Electrochemical Impedance ◽  
Open Circuit ◽  
Nyquist Plot ◽  
Alloy Matrix ◽  
Plating Bath ◽  
Transfer Resistance ◽  
Ni Alloy ◽  
Electroless Ni

Zinc and copper addition into electroless Ni-P alloy matrix produces quaternary Ni alloy that exhibits lower corrosion resistance behavior compared to Ni-P and Ni-Cu-P alloy in 3.5 wt% NaCl solution. The corrosion behavior of the alloy is previously studied using the anodic polarization curve measurement. The results show that the corrosion potential of different alloy composition is almost similar to each other for electroless Ni-Zn-Cu-P alloy. However, the surface resistance of the alloy needs to be confirmed by using electrochemical impedance spectroscopy. The alloy was first deposited on an iron substrate using electroless Ni alloy deposition method approximately similar thickness at different plating bath pH of 8.50 and 9.50. The Ni alloy coated substrate was used as working electrode immersed into a solution of 3.5 wt% NaCl. The electrochemical cell consists of Pt and Ag/AgCl/KCl (saturated) as counter and reference electrode respectively. Electrochemical impedance measurement was done at open circuit potential. The measurement started from 100 kHz to 10 mHz with 10 mV of sinusoidal perturbation applied to the cell. Other types of alloy including Ni-P, Ni-Cu-P and Ni-Zn-P, were compared with Ni-Zn-Cu-P alloy. From the results, the Ni-Zn-Cu-P exhibits the lowest corrosion behavior compared to other Ni alloy due to low charge transfer resistance (Rct) observed small inductive loop at low frequency region of the Nyquist plot. Furthermore, the Nyquist plot for Ni-Zn-Cu-P for pH 8.50 and 9.50 showed comparable result; hence, the effect of pH has less effect on corrosion resistance of the electroless Ni-Zn-Cu-P alloy.

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