PSZ 19:16 (Pind. 1/07)
HIGH SPEED NICKEL PLATING ON DIFFICULT TO
PLATE METAL (ALUMINIUM)
NORZIANA BINTI LANI
UNIVERSITI TEKNOLOGI MALAYSIA
PSZ 19:16 (Pind. 1/07)
HIGH SPEED NICKEL PLATING ON DIFFICULT TO
PLATE METAL (ALUMINIUM)
NORZIANA BINTI LANI
A project report submitted in partial fulfilment of the
requirements for the award of the degree of
Master of Engineering (Materials)
Faculty of Mechanical Engineering
Universiti Teknologi Malaysia
NOVEMBER 2010
iv
For my beloved mother, father,
family and all my friends
v
ACKNOWLEDGEMENT
In the name of Allah, the Most Merciful and Most Beneficent
It is with the deepest senses of gratitude I acknowledge that Almighty Allah gave me
the strength and ability to complete this research work and write this thesis. I would
like to express my sincere thanks to Dr. M. Sakhawat Hussain, my supervisor, for
allowing me to use his award winning equipment for high speed plating and for all
his guidance and encouragement that he provided in the course of this research work
at Universiti Teknologi Malaysia, Skudai. His time, patience, consideration and also
his creative ideas are greatly appreciated. I would also like to thanks all technicians
for their help during my experiment. Their careful amendments and creative ideas are
greatly appreciated. In addition, I would also like to thank to all my friends who
sacrificed a lot of their time to help me with my research. Last but not least, I would
like to thank my parents and my family for their love and encouragements.
vi
ABSTRACT
Aluminium has been widely used in many field of application due to the low
density, sensitive to corrosion, high mechanical strength and ease of fabrication.
Plating of metal on aluminium is complex and difficult because aluminium always
reacts with air to form oxide. It is difficult to obtain a good adhesive property on the
aluminium surface. Thus, to plate metal on the aluminium, oxide layer must be
eliminated by using an intermediate pre-treatment. However, this process involves
several steps and even then the level of addition between the plated metal and the
aluminium part is poor. The object of this project was to investigate the possibility of
plating nickel directly on aluminium surface without any pre-treatment process,
investigating the level adhesion between the deposited nickel and the aluminium base
by high speed electroplating technique and also to investigate the effect of current
density, temperature and different type of solution on weight of plated sample,
thickness of plated sample and rate of deposition. The level adhesion of the nickel
coating was determined qualitatively by using Adhesion Testing while morphology
and thicknesses of Ni plated was studied using Scanning Electron Microscopy
(SEM). It was found that the level of adhesion between nickel and aluminium
became low at current density above 1.0 A/cm2 and Ni plated was found to peel off
easily. Besides, by increasing the current density and temperature the weight and
thickness of Ni plated increase and sulphate based Ni solution gave much higher rate
of deposition compared to the traditional Watt’s based solution by increasing the
current density and temperature.
vii
ABSTRAK
Aluminium telah banyak digunakan dalam pelbagai bidang disebabkan sifat
ketumpatannya yang rendah, kekuatan mekanik yang tinggi dan mudah untuk
dibentuk. Penyaduran logam pada aluminium adalah sangat rumit dan sukar kerana
aluminium .sentiasa bertindak balas dengan udara untuk membentuk oksida. Ini
menyebabkan sukar untuk mendapatkan hasil lekatan yang baik pada permukaan
aluminium. Oleh itu, untuk menyadur logam pada aluminium, lapisan oksida perlu
dibuang dengan menggunakan pra-rawatan lanjutan. Namun begitu, proses ini
melibatkan beberapa langkah dan tahap lekatan antara logam dan aluminium tidak
begitu memuaskan. Objektif projek ini adalah untuk menyiasat kebolehan
penyaduran nikel secara lansung pada permukaan aluminium tanpa melakukan
proses pra-rawatan, menyiasat tahap lekatan antara nikel dan aluminium dengan
menggunakan teknik “High Speed Electroplating” dan juga untuk menyiasat
pengaruh ketumpatan arus, suhu dan jenis larutan pada berat, ketebalan, dan kadar
penyaduran yang dihasilkan. Tahap lekatan saduran nikel ditentukan dengan
menggunkan ujian perlekatan manakala morfologi dan ketebalan saduran nikel
ditentukan dengan SEM. Didapati bahawa lekatan antara nikel dan aluminium
menjadi rendah pada ketumpatan arus melebihi 1.0 A/cm2 dan saduran nikel yang
dihasilkan mudah tertanggal. Selain itu, dengan pertambahan ketumpatan arus dan
suhu, berat dan ketebalan saduran nickel juga bertambah. Larutan “Sulphate based
Ni” memberikan kadar penyaduran yang tinggi berbanding dengan larutan “Watt’s”
dengan pertambahan ketumpatan arus dan suhu.
viii
TABLE OF CONTENTS
CHAPTER
1.
2.
TITLE
PAGE
SUPERVISOR DECLARATION
ii
AUTHOR’S DECLARATION
iii
DEDICATION
iv
ACKNOWLEDGEMENT
v
ABSTRACT
vi
ABSTRAK
vii
TABLE OF CONTENTS
viii
LIST OF TABLES
xii
LIST OF FIGURES
xiii
LIST OF ABBREVIATIONS
xvi
LIST OF SYMBOLS
xvii
INTRODUCTION
1.1.
Background of the project
1
1.2.
Problem Statement
2
1.3.
Objectives
3
1.4.
Scope of the Project
3
1.5.
Structure of Thesis
4
LITERATURE REVIEW
2.1.
Overview of Electroplating
5
ix
2.2.
Introduction of Aluminium
7
2.3.
Problem of Plating on Aluminium
7
2.4.
Nickel Electroplating
10
2.5.
Type of Nickel Plating Solution
12
2.5.1. Watt’s Nickel Plating Solution
13
2.5.2. Nickel Sulphamate Solution
13
2.5.3. All Chloride Solution
14
2.5.4. Sulphate Chloride Solution
14
2.5.5. Fluoborate Solution
14
2.5.6. All-Sulphate Solution
15
2.5.7. Hard Nickel Solution
15
2.6.
Direct Nickel Plating on Aluminium
15
2.7.
High Speed Plating
18
2.8.
Factor Affect the Rate of Electroplating
20
2.8.1. Surface Preparation
20
2.8.2. Temperature
20
2.8.3. Current Density
21
2.8.4. Electrolyte
21
2.8.5. Anodes
22
2.8.6. Current Efficiency
22
2.8.7. Filtration
22
2.8.8. Anti Pitting
23
2.8.9. Air Agitation
23
Introduction of Porous Anodic Aluminium
23
2.9.
Oxide Film
2.10. Mechanism of Porous Anodic Aluminina
26
Formation
2.11. Disordered and Ordered of Pores of Anodic
Alumina Oxide Film
29
x
3.
4.
5.
METHODOLOGY
3.1.
Experimental Design
32
3.2.
Aluminium Sample Preparation
34
3.3.
Solutions Preparation
34
3.4.
Experiment Setup
35
3.5.
Sample Preparation
37
3.6.
Characterization
38
3.6.1. Morphology Analysis
38
3.6.2. Adhesion Testing
40
3.6.2.1.
Adhesion Test by Knife
41
3.6.2.2.
Adhesion Test by Tape
41
RESULTS AND DISCUSSION
4.1.
Introduction
42
4.2.
Nickel Plating Layer on Aluminium Sample
43
4.3.
Adhesion Analysis
43
4.4.
Morphology Analysis
44
4.5.
Effect of Current Density
49
4.6.
Effect of Temperature
51
4.7.
Effect of Type of Solution
54
CONCLUSION
5.1.
Conclusions
56
xi
6.
RECOMMENDATION
6.1.
REFERENCES
Recommendations
57
58
xii
LIST OF TABLES
TABLE NO.
TITLE
PAGE
2.1
Electrode potential for pure elements
8
2.2
Electrode potential for second phase elements
9
2.3
Coefficient of thermal expansion for the range of 0 o to
10
100oc
2.4
Composition for various electroplating solutions
12
3.1
Composition of solutions preparation
35
3.2
Summary of sample preparation according current
37
density and temperature for Watt’s solution
3.3
Summary of sample preparation according current
38
density and temperature for sulphate based Ni solution
3.4
Preparation method (ASTM E3)
40
4.1
Weight of plated layer by using Watt’s solution
49
4.2
Weight of plated layer by using sulphate based Ni
49
solution
4.3
Coating thicknesses by using Watt’s solution
51
4.4
Coating thicknesses by using sulphate based Ni solution
52
4.5
Deposition rate at different type of solution.
55
xiii
LIST OF FIGURES
FIGURE NO.
2.1
Mechanism
TITLE
of
electroplating
PAGE
and
structure
of
6
electroplated coatings
2.2
Schematic of the electrochemical plating of nickel
11
2.3
External potential versus limiting current density
19
2.4
The pore and hexagonal cell structure
24
2.5
The hexagonal arrays of porous oxide film
24
2.6
SEM micrographs of the bottom view of anodic alumina
26
layers. Anodization was conducted in (a) sulfuric acid,
(b) oxalic acid and (c) phosphoric acid. The thicknessof
the oxide film was approximately 120 µm
2.7
Porous anodic aluminium oxide film formation in term of
27
current and anodizing time
2.8
Schematic diagram of porous anodic alumina growth
29
2.9
The SEM images showing amorphous anodic aluminum
30
oxide layer produced in 10% phosphoric acid. (a) Plan
view of the surface of the porous anodic aluminium
oxide and (b) side profile of the aluminium with the
porous aluminium oxide/
2.10
SEM image of alumina pores array formed by two steps
31
anodic anodization.
3.1
Flowchart to conduct the electroplating process
33
3.2
Project specimen of aluminium rod
34
xiv
3.3
Schematic diagram of high speed plating equipment
36
3.4
High Speed Electroplating Equipment developed by
36
M.S.Hussain
3.5
Scanning Electron Microscope Equipment
39
3.6
Adhesion test by using knife
41
4.1
Nickel plating on aluminium sample
43
4.2
Nickel plated sample for (a) Good Ni adhesion and (b)
44
poor Ni adhesion on aluminium
4.3
Cross section nickel plated on aluminiun surface
45
morphology under 2000x Magnification.
4.4
The EDAX analysis for 55oC temperature and 0.3A/cm2
45
current density by Watt’s solution
4.5
Cross-section Ni plated on aluminium surface at 55oC for
46
(a) 0.1A/cm2, (b) 0.3A/cm2 and (c) 0.6A/cm2 current
density.
4.6
Cross-section Ni plated on aluminium surface at 60oC for
46
(a) 0.1A/cm2, (b) 0.3A/cm2 and (c) 0.6A/cm2 current
density.
4.7
Cross-section Ni plated on aluminium surface at 65oC for
47
(a) 0.1A/cm2, (b) 0.3A/cm2 and (c) 0.6A/cm2 current
density.
4.8
Cross-section Ni plated on aluminium surface at 55oC for
47
(a) 0.1A/cm2, (b) 0.3A/cm2 and (c) 0.6A/cm2 current
density.
4.9
Cross-section Ni plated on aluminium surface at 60oC for
48
(a) 0.1A/cm2, (b) 0.3A/cm2 and (c) 0.6A/cm2 current
density.
4.10
Cross-section Ni plated on aluminium surface at 65oC for
(a) 0.1A/cm2, (b) 0.3A/cm2 and (c) 0.6A/cm2 current
density.
48
xv
4.11
Influence of current density on weight of Ni plated layer
50
by using Watt’s solution
4.12
Influence of current density on weight of Ni plated layer
50
by using sulphate based Ni solution
4.13
Influence of temperature on coating thickness by using
52
Watt’s solution
4.14
Influence of temperature on coating thickness by using
53
sulphate based Ni solution.
4.15
Influence of different type of solution on deposition rate
55
xvi
LIST OF ABBREVIATIONS
Al
-
Aluminium
ASTM
-
American Society for Testing and Materials
CuAl2
-
Cuprum Alumina
CuMgAl2
-
Cuprum Magnesium Alumina
EDAX
-
Energy Dispersive Spectroscopy
FeAl3
-
Ferum Alumina
Mg
-
Magnesium
Mg2Al3
-
Magnesium II Alumina
MgZn2
-
Magnesium Zinc
MnAl6
-
Manganese Alumina
Ni
-
Nickel
NiAl3
-
Nickel Alumina
SEM
-
Scanning Electron Microscope
Si
-
Silicon
Zn
-
Zinc
xvii
LIST OF SYMBOLS
aMZ+
-
Bulk activity
D
-
Diffusion of Coefficient of MZ+
e-
-
Electron
iL
-
Limiting Current Density
t
-
Transport number
V
-
Electrode Potential
δ
-
Thickness
1
CHAPTER 1
INTRODUCTION
1.1
Background of the Project
The process for nickel plating on aluminum has advanced over the past
decade from a rather complicated technology to a very consistent, easily
reproducible procedure (George and Chadd, 2009). As a consequence of the
continuous improvement in processing techniques, nickel plating is being relied
upon more as a finish of choice by design engineers looking for lightweight, high
strength materials in the manufacture of their products (George and Chadd, 2009;
Mest, 2009). While aluminum has a good strength-to-weight ratio and excellent
machinability, nickel plating can extend the ability of aluminum to function in
applications where it could not be considered otherwise. Friction, wear and
appearance are greatly enhanced by applying specific electroplating nickel
coatings. For electronics applications, high phosphorous electroplating nickel can
provide non-magnetic properties, corrosion resistance and extended wear.
2
The plating of metals on aluminium is a complex and highly developed
(Satee and Schaumburg, 1980; Cooper et al., 1961; Bornhauser et al., 1932). For
the most part, when it is desired to coated nickel on aluminium, the practice has
been first to plate the aluminium with an intermediate layer of copper (Satee and
Schaumburg, 1980). The nickel coating is then superimposed on the copper film,
after which the object may be further processed by applying an outer chromium
coating, if desired. In other processes the aluminium is first dipped in a cadmium
plating bath, after which the article is electroplated or otherwise coated with such
metal as copper, nickel, tin or any of other various metals as desired (Satee and
Schaumburg, 1980; Cooper et al., 1961). In other processing techniques known as
zincate process and the stannate process, a thin coating of zinc or tin is applied to
the aluminium prior to the subsequent electrolytic deposition of other coating
metals. But, these processes always require a copper or a bronze strike to prevent
dissolution of the zinc or tin in the nickel bath (Kampert and Burell, 1976).
This project relates to a process for depositing a film or coating of nickel
directly on articles of aluminium without the need to preplate or otherwise to coat
with an intermediate layer such as copper, zinc or cadmium.
1.2
Problem Statement
Generally, electroplating method nickel on aluminium has been developed,
but through this method involves several steps for plating nickel on aluminium by
using an intermediate pre-treatment process and the deposition of a zincate layer
(Miller, 1972). This is because oxide layer forms almost instantaneously on the
aluminium surface. Because of the presence of oxide layer on aluminium surface, it
is difficult to obtain a good adhesive property on the aluminium surface (Topelian
and Newark, 1958; Kampert and Burell, 1976). Beside, the level addition between
3
the nickel plating and the aluminium part is poor (Frasch, 1941). Because of this
problem the high speed plating method is chose to plate the nickel on aluminium.
1.3
Objectives
The main objective of this research is to find out the possibility of nickel
plating directly on aluminium surface without any pre-treatment process. The study
also includes investigating the level adhesion between nickel and aluminium by high
speed electroplating technique. The third objective is to investigate the effect of
current density and temperature on weight and thickness of nickel plating layer. The
fourth objective is to investigate the effect different type of solution on deposition
rate of nickel plated.
1.4
Scope of the Project
This project consists of three main tasks which include:
1.
Deposition of nickel surface finish. The deposition of Ni will be
conducted by high speed electroplating process on aluminium
substrate.
2.
The selection and determination of nickel plating parameters and also
to design the experiment for high speed nickel electroplating process
on aluminium.
3.
Characterize the level of adhesion between nickel and aluminium and
the thickness of Ni plated.
4
1.5
Structure of Thesis
The thesis comprise of six chapters. The first chapter is the introduction,
which clearly define the objective and scope of this project. Chapter two consists of
literature review. In this chapter, it explains the problem of plating on aluminium,
conventional plating process on aluminium, high speed electroplating process and
lastly the porous anodic aluminium oxide film.
Chapter three is the experimental methodology. In this chapter, a detailed
account of materials, setup and procedures followed in the experimental work of this
thesis are discussed thoroughly. Chapter four contains the results and discussion
obtained from the experimental work conducted. Chapter five included the
conclusion drawn based on the results and lastly, the final chapter, chapter six
included the recommendations by the author for future work.
5
CHAPTER 2
LITERATURE REVIEW
2.1
Overview of Electroplating
Electroplating is often also called "electrodeposition", and the two terms are
used interchangeably. As a matter of fact, "electroplating" can be considered to occur
by the process of electrodeposition. Electrodeposition is the process of producing a
coating, usually metallic, on a surface by the action of electric current (Schlesingerl,
2002). If a metal object is placed in an aqueous solution of a salt of the same metal or
a different metal and supplied with a strong cathodic electric potential, electroplating
of the metal object may occur. Electroplating is caused by cathodic reactions leading
to the reduction of metal from solution and evolution of hydrogen or oxygen. Typical
examples of electroplating mostly involve aluminium or steel as the substrate and
metals such as nickel chromium and cadmium as the plating metal. Electroplating is
performed in large tanks of metal salt solution with an attached power supply and
immersed metal (nickel) that functions as the anode. The range of metals that can be
electroplated (Krishnam and Sanjeeb, 2007).
6
The formation of metal film on a substrate from metal ions in aqueous
solution is a complex process that is still not fully understood. In most instances, this
film formation process functions well without external intervention and is therefore
usually overlooked. It is believed that electroplated coatings begin as small nodules
of deposited metal, which then grow laterally to form a coating. The coating contains
flaws at the boundary where the growth of one nodule joins the growth of another
nodule. The principle of electroplating and structure of electroplated coatings are
illustrated schematically in Figure 2.1 (Krishnam and Sanjeeb, 2007).
(a) Electroplated coatings
(b) Mechanism of coating formation
Figure 2.1: Mechanism of electroplating and structure of electroplated coatings
(Krishnam and Sanjeeb, 2007).
7
2.2
Introduction of Aluminium
Aluminium has been widely used in many field of application, generally in
electronic application and aerospace industries. There are three main properties
which make aluminium an interesting base material which are low density of
approximately 2.7g/cm3, sensitivities to the corrosion, high mechanical strength that
is achieved by suitable alloying and heat treatments. Besides, it has other properties
that are included in the aluminum such as high thermal and electrical conductance,
high ductility, magnetic neutrality, high scrap-value and the non-poisonous and
colourless nature of its corrosion products, which facilitates its use in the chemical
and food processing industry (Luan et al., 2004).
Aluminium in its pure state has a relatively high corrosion resistance and
needs less protection than most metals. However, the commercial aluminium alloys,
though mechanically more versatile are distinctly more sensitive to corrosion, and
the development of high strength light alloys, containing quantities of heavy metal
such nickel, copper or zinc has heightened the need for protective surface treatments.
The nature of the heavy metal additions appreciably influences the alloy’s
susceptibility to corrosion, and high mechanical strength and corrosion resistance
have so far proved largely incompatible. The development of satisfactory protective
finishes for these metals has been, therefore, of significant importance (Luan et al.,
2004).
2.3
Problem of plating on Aluminium
There are a number of difficulties to be considered when electroplating on
aluminium. One of the major things to be considered when plating on aluminium is
the condition of aluminium always react with the air to form oxide. It is difficult to
8
obtain a good adhesive property on the surface of aluminium due to the existence in
the passive state of an oxide coating on the aluminium (Tsukamoto et al., 1978;
Bornhauser et al., 1932; Kampert and Burell, 1976). It is important to note that
aluminium is amphoteric i.e. aluminium can be dissolved in both acidic and alkaline
solution. Due to the reactivity of aluminium unwanted ion-exchange processes are
also likely to occur in the plating solution. All of these characteristics can be
eliminated by using an intermediate pre-treatment layer deposited by zincate process
(Tsukamoto et al., 1978; Moller, 1994; Satee and Schaumburg, 1980). According to
Luan et al., (2004) two basic methods of pre-treatment have been developed which
are the formation of a thin immersion coated layer of zinc, tin, iron, nickel and the
treatment of a porous oxide film by chemical or anodic oxidation (Luan et al., 2004).
Second problem to plate on aluminium is the electrode potential value of
aluminium compared to some other metals. Its shows that difference between
aluminium matrix and pure elements as well as second phase constituents can affect
the deposition reaction. Table 2.1 and Table 2.2 show the electrode potential for pure
elements and second phase elements. The position of aluminium in the
electrochemical series can lead to the formation of immersion deposited in the
plating solution. Because of this problem, some treatment should be taken when
plating on aluminium to avoid alloying elements giving big electrode potential
difference leading to unwanted electrochemical actions during the plating process
(Moller, 1994a; Moller, 1994b).
Table 2.1: Electrode Potential for pure elements (Moller, 1994a)
Elements
Electrode potential (V)
Al (99.5%)
-0.83
Al (99.5%)
-0.85
Zn
-1.10
Mg
-1.73
9
Table 2.2: Electrode Potential for second phase elements (Moller, 1994a)
Elements
Electrode potential (V)
Si
-0.26
NiAl3
-0.52
FeAl3
-0.56
CuAl2
-0.73
MnAl6
-0.85
CuMgAl2
-1.00
MgZn2
-1.05
Mg2Al3
-1.24
The coefficient of thermal expansion of aluminium and its alloys differs from
most of the metals commonly deposited. The coefficient of thermal expansion of
aluminium gives the higher values compared to other metals. The consequence is that
if the plated specimen is subjected to a temperature elevation the coating is
mechanically stressed differently than the substrate and then can cause decohesion of
the coating or form cracks through the coating. It frequently happens if the coating
adhesion to the substrate or the pretreatment layer is poor decohesion of the coating
can occur. Table 2.3 shows the coefficient of thermal expansion for the range of 0 o to
100oC (Moller, 1994a; Moller, 1994b).
Plating on aluminium is a relatively expensive technique to apply in industry.
However, plating on aluminium is an increasingly important technique in the
industry because of the possibility to combining the low density of aluminium with
the functional properties of the deposit. When plating on aluminium, the difference
in atomic diameter and crystal lattice structure between the aluminium substrate and
the metal deposited on it must be considered. The good results can be obtained with
a suitable combination of metal and process. The achievable properties that can be
added to aluminium are mechanical, magnetic, electrical, thermal, corrosive and
decorative (Moller, 1994a; Moller, 1994b).
10
Table 2.3: Coefficient of thermal expansion for the range of 0 o to 100oC (Moller,
1994a)
2.4
Elements
Coefficient of thermal expansion
Chromium
7 x 10-5 / oC
Steel
12
Nickel
13
Gold
14
Brass
18
Copper
18
Silver
19
Aluminium
24
Tin
27
Zinc
27
Cadmium
31
Nickel Electroplating
Nickel coatings are most widely used for their high corrosion, coupled with
an attractive visual appearance. Thus, taps and sanitary ware, automotive
components and light fittings are but a few examples of this widely used coating. In
electroforming, nickel coatings are widely used for their hardness, wear and
corrosion-resistance (Nasser, 2004). Nickel electroplating is a process of nickel
deposition on a part, immersed into an electrolyte solution and used as a cathode,
when the nickel anode is dissolved into the electrolyte in the form of the nickel ions,
travelling through the solution and depositing on the cathode surface (Dibari, 2000).
Electrodeposited nickel can be strong adherent, ductile and resistant to corrosion,
erosion and wear. Its mechanical properties can be varied at will between wide limits
by changing plating conditions, by alloying with other elements, and by
11
incorporating particles and fibers within the electrodeposited nickel matrix (Liona,
2005).
The process of nickel electroplating involves the dissolution of one electrode
(anode) and the deposition of metallic nickel on the other electrode (cathode). The
schematic of nickel electroplating cell is shown in Figure 2.2. Direct current is
applied between the anode (positive) and the cathode (negative). When the power
supply is turned on, the positive ions in the solution are attracted to the negatively
biased cathode. The nickel ions that reach the cathode, gain electrons and are
deposited on the surface of the cathode forming a layer. Simultaneously, another
reaction that depends on the nickel solution used to plate, occurs at the anode, to
produce ions and electrons for the power supply (Dibari, 2000).
Figure 2.2: Schematic diagram showing the set-up of electrochemical plating of
nickel (Liona, 2005)
12
2.5
Type of Nickel Plating Solution
Various types of nickel plating solutions are used in depositing nickel these
are Watts nickel plating solutions, nickel sulphamate solutions, all-chloride solutions,
sulphate-chloride solutions and fluoborate solutions. Table 2.4 shows various
electroplating solutions that are used in industry.
Table 2.4: Composition for Various Electroplating Solutions
Electrolyte Composition (oz/gal)
Composition
Nickel Sulphate,
NiSO4.6H2O
Watts
20 to 40
High
All
chloride
Chloride
Fluoborate
Sulphamate
32
Nickel
Fluoborate
45 to 60
Ni(SO3HN3)2
.4H2O
Nickel Chloride
NiCl2.6H2O
Boric Acid
H3BO3
6 to 12
12
32
4 to 6
4 to 5
4
0 to 3
4
4 to 6
Operating Conditions
Temperature oF
90 to 160
100 to 160
100 to 145
90 to 160
90 to 140
10 to 60
10 to 60
50 to 100
50 to 100
5 to 260
Anodes
Nickel
Nickel
Nickel
Nickel
Nickel
pH
2 to 5.2
2 to 2.5
0.9 to 1.1
3.0 to 4.5
3.5 to 4.5
Cathode Current
Density (asf)
13
2.5.1 Watts Nickel Plating Solutions
The most common nickel plating bath is the sulphate bath known as the
Watt’s bath. Watt’s solution was developed by Oliver P. Watts in 1916 (Kopeliovich,
2010; Graves, 2009). Plating operation in Watt’s solutions is low cost and simple
(Kopeliovich, 2010). Watt’s bath contains three different solutions which are nickel
sulphate, nickel chloride and boric acid. The large amount of nickel sulphate
provides the necessary concentration of nickel ions. Nickel chloride improves anode
corrosion and increases conductivity. Boric acid is used as a weak buffer to maintain
pH. The Watt’s bath has four major advantages which are simple and easy to use,
easily available in high purity grades and relatively inexpensive, less aggressive to
plant equipment than nickel chloride solutions. The deposits plated from these
solutions are less brittle and show lower internal stress than those plated from nickel
chloride electrolytes (Graves, 2009).
2.5.2 Nickel Sulphamate Solutions
Nickel sulphamate solution is used for electroforming and for producing
functional nickel coating. Nickel coatings deposited nickel sulphamate baths possess
lowest internal stress. High nickel concentrations of sulphamate electrolytes permit
to conduct electroplating at high current densities (Kopeliovich, 2010). Nickel
coatings from nickel sulphamate usually have very low stress values and high
elongations. Another advantage is that it is possible to operate the sulphamate bath
without difficulties related to anode dissolution at low chloride levels or even
without chloride. The principle advantage of this bath is that it can be operated at
nickel concentrations of 180-200 g/liter. This allows for the use of high current
densities without losing the properties of the coating (Graves, 2009).
14
2.5.3 All-Chloride Solutions
All-Chloride solutions operate at low voltage and permit deposition of thick
coatings (Kopeliovich, 2010). The advantages of all-chloride solutions include the
low voltage, good polishing characteristics, heavy coatings can be deposited, low
pitting, improved cathode efficiency and no need to cool the plating solution
(Graves, 2009). However, there are disadvantages to this bath. The main
disadvantage of all-chloride baths is high internal stress of the coating (Kopeliovich,
2010). Another disadvantages include highly corrosive, nickel chloride is sometimes
less pure than nickel sulphate and mechanical properties of the deposit are not as
good as those from the Watts bath (Graves, 2009).
2.5.4 Sulphate-Chloride Solutions
Sulphate-chloride solutions produce depositions with internal stress lower
than the all-chloride solutions. Sulphate-chloride bath operate at voltages lower than
Watts baths. This type of electrolyte permit deposition at high rates (high electric
current) as compared to Watts bath (Kopeliovich, 2010).
2.5.5 Fluoborate solutions
Fluoborate solutions permit high rate depositions due to higher (than in
Watt’s solution) nickel concentration. Fluoborate solutions are mainly used for
electroforming and for deposition of thick coatings (Kopeliovich, 2010). Anode
dissolution in a nickel fluoborate bath not containing chloride is better than in a
nickel sulphate solution with nickel chloride. The disadvantages of fluoborate baths
include the high cost of chemicals and throwing power less than that of sulphate
solutions (Graves, 2009).
15
2.5.6 All-Sulphate Solutions
All-Sulphate solution are used mainly in applications where insoluble anodes
are required (plating tubes and small fittings) (Kopeliovich, 2010).
2.5.7 Hard Nickel Solutions
Hard nickel solutions are used in applications where high tensile strength and
hardness are required (Kopeliovich, 2010).
2.6
Direct Nickel Plating on Aluminium
Nickel plating on aluminium is one of the most versatile surface finish
processes. Electroplated nickel is used extensively in many engineering applications,
ranging from simple thin film for decorative purpose to corrosion and wear resistant
coatings (Oliveira et al., 2006). The plating of nickel on aluminium is a complex and
highly developed art (Satee and Schaumburg, 1980). Therefore, it has been
considered to be extremely difficult on nickel plating to obtain a good adhesive
property on the surface aluminium and aluminium alloys due to the existence in the
passive state of an oxide coating on the aluminium (Tsukamoto et al., 1978).
Therefore, many processes have been made prior to nickel plating on aluminium to
overcome this problem.
According to the Tsukamoto et al., (1978), the principal processes that
currently used in industry can be generally classified into three types which are
chemical plating process, anodized nickel coating process and molten metal plating
16
process (Tsukamoto et al., 1978). These three methods also known as indirect nickel
plating. A chemical plating process is a process which first deposits a zinc layer upon
an aluminium article by immersion, then deposit a copper on zinc layer by
electrodeposition and firmly electroplated nickel on the copper layer (Asada, 1970).
However, this process cannot withstand the severe condition of use due to the
insufficient adhesive property between aluminium substrate and the plated metal
(Tsukamoto et al., 1978). In addition, not all metal can be deposited onto zinc
surface, thus special precaution are necessary because the zinc layer is very thin and
any treatment which penetrates the zinc layer would attack the underlying aluminium
and will result in a poor deposit (Topelian and Newark, 1958).
Anodized nickel coating process is a process which first anodizes the
aluminium article and then electroplates nickel on the coating produced by the
anodization (Asada, 1970). This process provides usual adhesive property but have
problem of quality limitation regarding the aluminium substrate as the chemical
plating process. The third process is hot dipping process wherein a metal of low
melting temperature is heated until molten and aluminium is immersed in the molten
metal. This process give some advantages where the substrate aluminium would not
be limited as to quality as in the chemical plating process and anodized process and
also give a good adhesive property. However in this process, the large amount of
heat source needed its inferior to the former two processes in producing an
aluminium material in an annealed and soft condition and also presents a poor visual
appearance (Tsukamoto et al., 1978).
According to previous researchers all these three methods suffer from the
disadvantages of involving several steps (Miller, 1972). According to Asada (1970)
each method is complicated by necessity for repeated steps of etching by acids and
alkalis of various kinds as well as rinsing in water. In addition, the selection of
treating solution, including etching and washing and combination of treating process
must be changed in accordance with the kind of base metal aluminium metal being
plated (Asada, 1970). Another research found that, plating nickel on aluminium is a
process reduction of the thin film of oxide on the metal, often include preliminary
17
coating such as copper, zinc or iron either by chemical transfer or electrolysis and the
result in these method have not usually given satisfactory in the industrial
application, since the alumina film is one more formed if the reduction is not
instantaneously followed by the first chemical or electrolytic coating. Besides, the
aluminium can be attacked by chlorides in which alumina will be dissolved and thus
give unsatisfactory results owing to the absorption of chlorine compounds in the
porosity of the metals, in which such chlorine will remain even after the subsequent
electrolytical deposition. Although nickel plating is initially quite adherent, the
absorbed chloride is liable to cause a separation of the nickel plating after a time, and
especially when the temperature is raised (Frasch, 1941).
All of these inconveniences in an indirect nickel plating processing were
drawing the attention of researchers to make active investigation on direct nickel
plating on aluminium. Direct nickel plating on aluminium is a process for the
deposition of nickel directly on aluminium without the need to pre-plate or otherwise
to precoat with an intermediate metal layer such as copper (Satee and Schaumburg,
1980). Based on previous research, direct nickel plating on aluminium offered some
advantages compared to the indirect nickel plating such as the process is extremely
simple wherein no equipment required other than what is ordinary used in carrying
out conventional electrolytic process. The process is easy to prepare for plating by
using conventional prewashing or pre-etching solution (Satee and Schaumburg,
1980). Plating of nickel directly onto the surface of aluminium metal would give a
corrosion protection of the metal surface that provided by such a coating. A nickel
coating also serves as an excellent substrate for receiving a coating of another metal
which may be deposited by either electroless or electrolytic means (Miller, 1972).
According to Satee and Schaumburg (1980) in direct nickel plating process, it
is necessary only to rinse the pre-cleaned articles well with water prior to immersion
in the treating composition which constitutes the preferred formulation. In addition,
Satee and Schaumburg (1980) found that when nickel is only metal introduced into
the plating tank, the plating bath is effectively protected from contamination. Other
than that, a related advantages of a direct nickel plating process is that the need for a
18
strike bath process in indirect nickel plating can be eliminated, thus there being only
nickel as the metal constituent in the plating system. By referring to the results
obtained in the previous research, direct nickel plating give highly effective and
produces products of excellent quality, with significant saving in material, time and
manufacturing costs. This is because it is carried out in a series of simple steps (Satee
and Schaumburg, 1980; Miller, 1972).
2.7
High Speed Plating
The rate of electrodeposition, being governed as it is by Faraday’s law,
depends directly upon the current density applied on the cathode, but this current
density has a liminiting value above which acceptable plate is not obtained. The
anion present in the nickel plating bath can affect this limiting current density,
chloride and sulphamate ions being markedly beneficial in raising it. The use of
nickel chloride solutions has been investigated by Wesley et al. amongst others,
claims being made that, with a solution velocity of 0.38m/s, sound deposits could be
obtained at 450 A/dm2. Sulphamate bath have been described in detail in many
papers which Hammond had reviewed (Dennis and Such, 1993).
The rate at which the electrolyte solution passes over the surface of the
cathode has a considerable effect on the maximum current density at which
satisfactory electrodeposits are obtained. This has been recognized for many years
and was the reason for the introduction first of cathode movement, usually at the rate
of about 0.1 m/s, and then air agitation, as means of providing solution movement
over the cathode and thus reducing the thickness of the diffusion layer (Dennis and
Such, 1993).
19
Current density increases as the applied external potential increases until the
limiting current density is reached, as shown in Figure 2.3. Concentration
polarization is largely responsible for this phenomenon.
𝒊𝑳 =
𝑫𝑴𝒁+ 𝒛 𝑭𝒂𝑴𝒁+
𝒙 𝟏𝟎−𝟏
𝟏−𝒕 𝜹
where iL. the limiting current density, is in A/dm2, D is the diffusion coefficient of
MZ+ in cm2/s and aMz+ its bulk activity in g ions/l, δ is the thickness of the diffusion
layer in cm and t is transport number of MZ+. This equation shows the effect of D, a
and δ on the limiting current density. Means of changing these terms in order to
increase current density, however, it should be emphasized that the only way of
obtaining a large increase in current density is to reduce δ, the thickness of the
diffusion film. This is achieved by some means of agitation of the plating solution
movement of the cathode. All methods of high speed plating are designed with this
objective in mind (Dennis and Such, 1993).
Figure 2.3: Electrode Potential versus Limiting Current Density (Dennis and Such,
1993).
20
2.8
Factor Affect the Rate of Electroplating
There are many factors that affect the electroplating process. The surface area
of the electrodes, the temperature, the kind of metal and the electrolyte, the
magnitude of the applied current are some of these factors.
2.8.1 Surface Preparation
For good quality electroplating and good adhesion of the deposit, the
condition of the surface to be plated is important. Most plating defects arise from
unclean surfaces prior to plating. The surface to be plated must be clean and free
from grease, dirt, oxides and tarnish films, polishing compounds, etc. Greasy, dirty
surfaces will not be wetted by the electrolyte and may not be plated. It also helps to
have a smooth polished surface, free from defects and imperfections, if one wants a
bright polished electroplated deposit. Plating should not be used to hide defects and
to improve the surface polish (reduction in surface roughness). Defects to be avoided
include casting porosity, inclusions and embedded polishing compounds, scratches
and tool marks, and pitting from over-pickling (Cristopher, 2002).
2.8.2 Temperature
The temperature of the electrolyte can also play a role in getting good plating,
particularly in alloy plating. Nickel electroplating processes are conducted at
increased temperature, which results in lower electrolyte resistance and therefore
permits to decrease the voltage. Additionally higher temperatures aid dissolution and
prevent precipitation of boric acid and other components (Gay et al., 1988).
21
2.8.3 Current Density
The electrical conditions during plating are also important for plating quality.
In particular, the current density (the current divided by surface area of the piece)
plays an important role, particularly in alloy plating where deposit composition is
controlled by current density. If the current is too high, the plating speed is increased
but one may get a porous, dendritic deposit rather than a bright one and it may be
accompanied by gas evolution which affects the surface finish. If it is very low, then
the deposit may not have a good appearance and plating will be slow (Christopher,
2002). One way to avoid working at lower current densities is by employing a
discontinuous direct current to the electroplating solution. By allowing between one
and three seconds of break time between every eight to fifteen seconds of electrical
current, high current densities can produce a higher level of quality. A discontinuous
current is also beneficial for avoiding over-plating of specific sections on the base
material (Hibbard et al., 2008)
2.8.4 Electrolyte
A good electrolyte will contain the metal (or metals) to be deposited in solution
in a sufficient concentration. In cyanide based gold baths, this will be in the form of
gold potassium cyanide salt. It will also contain other additives to give good plating
properties, These include, for example, additives to improve (Christopher, 2002):
1. The throwing power of the bath which means good uniformity of thickness
over the piece being plated.
2. The brightness of the deposit. Special brighteners are added to assist.
3. The internal stress in the deposit. These additives control the build-up of
stress to prevent cracking and spalling.
22
4. The chemical stability of the electrolyte and may include buffering agents to
control pH which is a measure of the acidity or alkalinity of the electrolyte.
2.8.5 Anodes
The anode area and position are important in order to obtain efficient
electrodeposition and uniformity of deposit. There is a tendency for plating to be
thicker on cathode areas closest to the anode and thinner in areas hidden (or out of
line of sight) from the anode. Correct positioning of the anodes (more than one may
be used) and a large anode area (compared to cathode area) is desirable for good
plating (Christopher, 2002).
2.8.6 Current Efficiency
Current efficiency is a ratio of the current producing nickel deposit to the
total passing current. Anode current efficiency in nickel electroplating is about
100%. It may decrease at high pH when nickel dissolution is accompanied by
discharging hydroxyl ions (OH -). Cathode efficiency of nickel electroplating is 9097%. 3-10% of the electric current is consumed by discharging hydrogen ions (H+),
which form bubbles of gaseous Hydrogen (H2) on the cathode surface (Gay et al.,
1988).
2.8.7 Filtration
Continuous filtration of nickel plating baths with active carbon filters permits
to control both presence of foreign particles and organic contaminations (products of
23
brightener decomposition etc). The filtration pumps should turn over the solution a
minimum 1-2 times tank volume per hour (Gay et al., 1988).
2.8.8 Anti Pitting
Hydrogen bubbles formed on the cathode surface and adhered to it may cause
pitting of the deposit. In order to enhance removal of the bubbles wetting agents are
added to the electrolyte. Wetting (anti-pitting) agents e.g. sodium lauryl sulphate
(SDS) decrease the surface tension of the cathode and force the hydrogen bubbles out
of the surface (Gay et al., 1988).
2.8.9 Air agitation
Air agitation by low pressure blowers is used in nickel electroplating to
enhance removal of the hydrogen bubbles discharged at the cathode (Gay et al.,
1988).
2.9
Introduction of Porous Anodic Aluminium Oxide Film
Since 1932, it has been known that the aluminium oxide layer consists of
three distinct layers; aluminium metal, a thin compact oxide layer (barrier layer) and
a porous oxide layer (Le et al., 1980; Juhl, 1999). The schematic diagram of oxide
layer shows in Figures 2.4. Figure 2.5, shows a plane view of the porous oxide layer.
The porous oxide layer is a relatively thick outer layer with regularly spaced pores
extending from the outer surface towards the aluminium metal, while the barrier
layer is located at the adjacent to the metal oxide interface (Miney et al., 2003).
24
Depending on the application of the anodic aluminium oxide film as template
for nano-structure materials, the characteristics of porous anodic aluminium oxide
film that play important roles in determining the properties of the nano-structure
from which formed by electroplating process on the anodic aluminium oxide
template are its pore’s diameter, pore array’s organization and also its porous layer
thickness.
Figure 2.4: The pore and hexagonal cell structure (Juhl, 1999)
Figure 2.5: The hexagonal arrays of porous oxide film (Juhl, 1999)
Anodic aluminium oxide thin film has attracted much attention in nanofabrication industry due to its self-organization properties that owing to the fact that
25
it enables mass production without the use of expensive lithographical tools, such as
an electron beam exposure system (Miney et al., 2003). As mentioned by Metzger et
al. (2000) ordered pores only occur in aluminium and no other metals. The highly
self-ordered hexagonal pore array of anodic aluminium oxide film was first found by
Masuda et al. (2004), by utilizing a prolonged anodization, followed by stripping of
the thick oxide and re-anodizing process (Metzger et al., 2000).
As explained by Metzger et al. (2000), and Ghorbani et al. (2006), the selforganized arrangements of neighboring pores in hexagonal arrays come from any
repulsive force interaction between the pores. According to the Li et al., (1998), a
possible origin of these forces between neighboring pores is the mechanical stress,
which is associated with the expansion during oxide formation interface and leads to
form curved shape metal/ porous oxide interface. It is claimed that the pores are
formed during electropolishing and/ or anodizing on the aluminium surface can
become hexagonally ordered at certain voltages and times of the initial
electropolishing or by long term anodization and re-anodizing or also by a dynamic
process depending on the mobility of ions within the barrier oxide and of aluminium
atoms within the metal.
It is well known that a porous anodized film is formed on the surface of
aluminium by anodization in acid or alkaline solution (Wada et al., 1986). Selforganized hexagonal pore arrays with a 50 – 420 nm inter-pore distance in anodic
alumina have been obtained by anodizing aluminium in oxalic, sulphuric and
phosphoric acid solution. Figure 2.6 represent the pore arrangement anodized in
sulphuric, oxalic and phosphoric acid solutions under optimum parameters, where
SEM micrographs of the porous films are shown with same magnification.
Hexagonal ordered pore arrays with distance as large as 420 nm were obtained under
a constant anodic potential in phosphoric acid. By comparison of the ordered pore
formation in the three types of electrolyte, it was found that the ordered pore arrays
in phosphoric acid show a polycrystalline structure of a few micrometers in size (Li
et al., 1998)
26
Figure 2.6: SEM micrographs of the bottom view of anodic alumina layers.
Anodization was conducted in (a) sulphuric acid, (b) oxalic acid and (c) phosphoric
acid. The thickness of the oxide film was approximately 120 µm (Li et al., 1998).
2.10
Mechanism of Porous Anodic Alumina Formation
The initial stages of oxide growth correspond to a relatively uniform oxide
thickness. But by the entrance of Al3+ ions into the electrolyte penetrations paths will
develop in top of the barrier layer. The local field will be concentrated in these
penetrations paths giving field strength of up to about 2.1 x 107 V/cm. Between these
penetration paths there will be a decrease in field strength and hence a decrease in the
27
field-assisted dissolution rate. The variation in field strength results the interface
aluminum/barrier layer to adopt the form of a fine scalloped structure. Concentration
of electric field and ionic current are higher at the bottom-middle region of the
scalloped structure and aid the formation of aluminum oxide layer. Based on this
theory, the influence of current and voltage behavior during anodization process need
to be taking in consideration (Juhl, 1999).
Figure 2.7 represents the current-anodizing time curved during porous anodic
alumina formation in anodizing process. At the beginning of period a, the current is
high due to the fact that the current only passes through the metallic aluminum.
Then, as time increase, the current is decreasing along with the formation of thin
compact aluminum oxide layer. This is because; oxide layer has higher resistance
than the metallic aluminum. The increase in thickness and therefore an increasing
resistance result in a further decrease in the current in period b (Juhl, 1999).
Compact
oxide layer
become
thicker and
roughened
Porous oxide
layer starts to
form
Porous
oxide
layer continue
to form with
constant current
Oxide layer
Metallic
aluminium
Figure 2.7: Porous Anodic Aluminium Oxide film formation in terms of current and
anodizing time (Juhl, 1999).
28
The increasing thickness of barrier layer will subsequently increase the
resistance and thus cause further decrease in current within period b. However,
within the period b, at certain point, the current-time curve tends to turn upward as
the current increases with time. This is due to roughness that forms on the top of
compact oxide layer (barrier layer).
The roughness of the barrier layer is built by the concentration of the current
in areas with thinner oxide than on the rest of the surface. The localized thinner oxide
areas are usually the subgrain boundaries found in aluminum. It was originally
suggested by Metzger et al. (2000) that the pores initiated at cracks or other defects
in oxide initially produced during anodizing. It appears, however, that any process
that thins the oxide locally can initiate pore formation. The natural oxide film on
either side of these subgrain boundaries is not compact or as uniform as on the rest of
the surface, thus it posses less electrical resistance which will become the places or
sites for initial pore cell formation to start (Metzger et al., 2000).
Then, in period c, the current is concentrated in areas with thinner oxide,
consequently increase electrolyte temperature at that area and results more
dissolution of compact alumina (barrier layer) layer. Then, the barrier layer become
even thinner and leads to increasing of current that favor the formation of porous
oxide layer to starts. This means that all oxides have been a part of the barrier layer
before becoming a porous oxide layer (Juhl, 1999). The current will increase up to
certain point where it becomes constant as in period d. This is where the formation
and dissolution of oxide layer process reach a steady level (occurs at same rate).
The growth of porous anodic aluminum oxide film (Figure 2.8) can be
concluded to involve below sequence (Wan , 2005):
a)
Formation of barrier layer.
b)
Pore nucleation due to local thickening of the oxide layer.
29
c)
Field enhanced oxide dissolution at oxide/electrolyte interface.
d)
Oxidation at the aluminum/oxide interface due to field enhanced
migration of O2- ions.
e)
Sustenance of pore growth due to the fact that electric field is highest
in the region around the pore bottom, leading to field assisted oxide
formation and growth of alumina side walls at the expense of field
assisted oxide dissolution at the pore bottom.
Figure 2.8: Schematic diagram of porous anodic alumina growth (Wan , 2005).
2.11
Disordered and Ordered Pores of Anodic Alumina Oxide Film
There are actually two types of aluminium oxide layer were formed during
anodizing which are disordered or amorphous pores formation and ordered
(crystalline) pores formation. The disordered pores arrangement can be formed in a
very wide processing using variety of a single acid solution such as sulphuric acid
(H2SO4), oxalic acid (H2C2O4), phosphoric acid (H3PO4), chromic acid (H2CrO4) or
by using the combination of two acids or with other organic solution such as ethanol.
30
Metzger et al. (2000) mentions that the pore growth rate is 0.1 µm per minute.
During the formation, amorphous and anhydrous alumina is formed but the pore
bottom of alumina may be partially crystalline (Metzger et al., 2000).
The image of disordered alumina pores is shown in Figure 2.9 below. Figure
2.7(a) shows a typical SEM image of the sample surface obtained after anodization
and Figure 2.7 (b) shows a cross section of the original aluminium and the porous
aluminium oxide layer. The surface image shows the pores of varying size and it is
difficult to know whether the cross-sectional image shows the widest wall-to-wall
distance or not because, it is not sure if the sample were cleavage down the center of
the pore. Miney et al. (2003) estimated the maximum pore width from those images
is approximately 100nm.
Figure 2.9: The SEM images showing amorphous anodic aluminum oxide layer
produced in 10% phosphoric acid. (a) Plan view of the surface of the porous anodic
aluminium oxide and (b) side profile of the aluminium with the porous aluminium
(a)
(b)
oxide (Miney et al., 2003).
As for the highly ordered pore formation as shown in Figure 2.10 (Singubara
, 2003), it has only narrow processing window and several methods has been found
such as long term-anodizing and re-anodizing steps and also initial electro polishing
to aid the highly ordered anodic aluminium oxide pores formation (Metzger et al.,
2000). Besides, highly ordered pores also have been produced by using imprint
periodic (pre-pattern) concave on aluminium metal to control pore initial position
(Singubara, 2003; Masuda et al., 2004). The methods of synthesizing highly ordered
31
hexagonal pores arrays in aluminium oxide are still intensively being studied due to
its application as templates in nano-structure fabrication industry.
Figure 2.10: SEM image of alumina pores array formed by two step anodic
anodization. (Singubara , 2003).
32
CHAPTER 3
METHODOLOGY
3.1
Experimental Design
The methodology of this research is to directly electrodeposit nickel on
aluminium by using high speed electroplating technique. High speed electroplating is
a technique where the high speed movement of the plating solutions is 2.7 m/s and
the high rate of plating is more than 600 μm/h (Hussain, 2009). In this research, three
parameters are involved during the electroplating processes which are different
values of current density, different values of temperature and different type of
solutions used. The type of nickel plating solution which will be used to plate nickel
on the aluminium is Watt’s bath solution and sulphate based Ni solution. Finally the
nickel deposits will be analyzed by using Scanning Electron Microscope (SEM) and
adhesion testing. Figure 3.1 shows the flowchart used to conduct the electroplating
process in order to achieve the study objectives.
33
Sample preparations
Anode: Nickel
Cathode: Aluminium
Current Density
Effect
Solution
Effect
Temperature
Effect
High Speed Plating
Process
Sample Testing
Microstructure Testing
 Scanning Electron Microscope (SEM)
Adhesion Testing
 Knife test
 Tape test
Documentation Test Result
Data Analysis
Discussion of Analyze Data
Conclusion and Recommendations
Figure 3.1: Flowchart to conduct the electroplating process.
34
3.2
Aluminium Sample Preparation
Specimen coupon size for the project study will be prepared where,
aluminium rod will be of diameter 10 mm and length 40 mm. Figure 3.2 illustrates
the dimension of the specimen coupon.
40 mm
10 mm
Figure 3.2: Project specimen dimensions of the aluminium rod
3.3
Solutions Preparation
In this experiment, two different solutions were prepared for plating nickel on
aluminium which are Watt’s solution and sulphate based Ni solution. Table 3.1
shows the summary of solution preparation according to their composition.
35
Type
Table 3.1: Composition of solution preparation
Typical
Cathode current
concentration
Constituents
density (A/dm2)
g/l
pH
Watt’s
NiSO4.7H2O
300
3.5 – 5.5
solution
NiCl2.6H2O
45
(Actual5)
H3BO3
38
Sulphate
NiCl2.6H2O
300
based Ni
H3BO3
38
2.5
Temperature
(oC)
2.5 – 10
45 – 100
(was varied)
(was varied)
2.5 – 10
50 – 70
Solution
3.4
Experiment Setup
Two specimens which are aluminium and nickel are placed at electrodes of
high speed plating equipment. Aluminium specimen was put at the cathode and
nickel specimen was put at anode. Nickel solution was put inside the solution bath
and the temperature of the nickel solutions is control by using temperature control
unit. Pump was turn on and the solution flows rapidly from the tank into the pipe
through the anode and cathode and returned back to the tank. Power generator was
turn on and the current density is adjusted. The electroplating process is performed at
fixed speed of 2.7 m/s and fixed times of 4 minutes. Figure 3.3 shows the schematic
diagram of the high speed plating equipment while Figure 3.4 show the high speed
plating equipment developed by M S Hussain (Patent pending).
36
Direct
current
Anode
Solution in
Solution out
Cathode
Pump
Tank
Figure 3.3: Schematic diagram of the high speed plating equipment developed by M
S Hussain (Patent pending)
Solution in
Solution out
Anode
Solution comes
from tank
Gap between
anode and
cathode ≤ 1mm
Pump
Cathode
Figure 3.4: High Speed Eletroplating equipment developed by M S Hussain (Patent
pending)
37
3.5
Sample preparation
Sample preparation for test on solution effect, current density effect and
temperature effect are discussed in this chapter. Each sample is coded as S/N which
means sample number of the specimen, for example S/N 1 means sample number
one. In solution or electrolyte preparation, Watt’s solution and sulphate based Ni
solutions are prepared as solutions in current density and temperature effect test.
Effect of current density studied by performing at 0.1 A/cm2, 0.3 A/cm2 and 0.6
A/cm2, while effect of temperature studied by performing temperature 550C, 600C
and 65 0C. Table 3.2 and Table 3.3 show the summary of sample preparation
according to the solution, current density and temperature.
Table 3.2: Summary of sample preparation according current density and temperature
for Watt’s solution
Current Density
Temperature
Sample Number
Solution
(A/cm2)
(0C)
S/ N 1
0.1
S/N 2
0.3
S/N 3
0.6
S/N 4
0.1
S/N 5
Watt’s solution
0.3
S/N 6
0.6
S/N 7
0.1
S/N 8
0.3
S/N 9
0.6
55
60
65
38
Table 3.3: Summary of sample preparation according current density and temperature
for sulphate based Ni solution
Current Density
Temperature
ample Number
Solution
(A/cm2)
(0C)
S/N 1
0.1
S/N 2
0.3
S/N 3
0.6
S/N 4
S/N 5
3.6
55
0.1
Sulphate based
Ni solution
0.3
S/N 6
0.6
S/N 7
0.1
S/N 8
0.3
S/N 9
0.6
60
65
Characterization
For sample testing analysis, the sample produced through high speed plating
method were tested and characterized by using scanning electron microscope (SEM)
and Adhesion Testing.
3.6.1 Morphology Analysis.
The morphology adhesion between the aluminium and nickel layer was
observed using Scanning Electron Microscope (SEM). Figure 3.5 show the Scanning
Electron Microscope equipment. SEM facilitates the observation of very fine details
(high resolution) of materials and good focus over a wide range of specimen surface
39
(large depth of field). It also produces clear image of specimen ranging from object
visible to the naked eye to a structure spanning few nanometers.
Beside, the
thickness of nickel layer will be determined to see the effect of different current
density, temperature and solution used during the experiment.
Figure 3.5: Scanning Electron Microscope (SEM)
The specimens for metallographic examinations were prepared according to
ASTM E3, Standard. Cleaning, grinding and polishing process in the specimen
preparation is required as to promote clean and good surface finish. Water is used to
remove the contaminants such as residue from grinder. Table 3.4 shows preparation
sequence consist of a series of grinding and polishing steps.
40
Process
Table 3.4: Preparation Method (ASTM E3)
Abrasive Type
Lubricant
Time (s)
ANSI
Planar Grinding
Stone 120 – 320
Water
15-45
Paper 240 grit SiC
Water
15-45
Paper 320 grit SiC
Water
15-45
Paper 600 grit SiC
Water
15-45
grit SiC/Al2O3
Fine Grinding
Rough Polishing
6μm diamond
Final Polishing
1μm diamond
Compatible
Lubricant
Compatible
Lubricant
120-300
60-120
Rotation
Complimentary
Rotation
Complimentary
Rotation
Complimentary
Rotation
Complimentary
Rotation
Complimentary
Rotation
Complimentary
Rotation
3.6.2 Adhesion testing
After the electroplating process, adhesion testing was required to quantify the
strength of the bond between the nickel layer and the aluminium substrate. Adhesion
testing in the paint and coating industries is necessary to ensure the paint or coating
will adhere properly to the substrates to which they are applied. The adhesion
between a coating and its substrate has been measured in various ways. For example,
coatings are often evaluated by a scratch test. A calibrated scratching tool is applied
to a test sample. A high quality adhesion between the coating and the substrate
prevents the penetration of the scratching tool and the workpiece passes. If the
adhesion is low, however, the tool can penetrate and scratch the coating, in which
case the sample fails.
41
In adhesion testing where the material of the coating is relatively hard, pull
tests are employed. A pulling apparatus having calibrated force and deflection
gauges is attached to the coating. The substrate is then held statically and force is
applied in a gradually increasing manner until the coating separates from the
substrate, whereupon the degree of force required to cause the separation is recorded.
However, in this study, two types of adhesion test are used which are adhesion by
knife and adhesion by tape test.
3.6.2.1 Adhesion Test by Knife
According ASTM D6677 – 07, this method is used to establish whether the
adhesion of a coating to a substrate or to another coating is at generally adequate
level by using a knife. Figure 3.6 show the adhesion testing using knife.
Figure 3.6: Adhesion test by using knife
3.6.2.2 Adhesion Test by Tape test
According ASTM D3359 – 09, this test method cover procedures for
assessing the adhesion of coating films to metallic substrates by applying and
removing pressures-sensitive tape over cuts made in the film.
42
CHAPTER 4
RESULT AND DISCUSSION
4.1
Introduction
This chapter will discuss the results of plating nickel on aluminium samples
that are produced via High Speed Electroplating Method. This result is divided into
two different analyses: which are adhesion analysis, and morphology analysis for
adhesion analysis, the samples were analyzed using the knife and tape test. For
morphology analysis, the samples were characterized using a Scanning Electron
Microscope (SEM) to measure the thickness of the layer. In this chapter, the effect of
current density, temperature and type of solution on weight of Ni plated, thickness of
Ni plated and rate of deposition are discussed.
43
4.2
Nickel Plating Layer on Aluminium Sample
In this research work, nickel plating layer on aluminium substrate has been
deposited using two different nickel solutions. Figure 4.1 show the sample of nickel
plating on aluminium. Figure also shows the original diameter for the sample. The
original diameter is 10 mm and ~ 10 mm thicknesses. From the observation of the
sample, it shows that no defect occur on the sample after plating process.
Nickel
Layer
Ø 10mm
Aluminium
Substrate
Figure 4.1: Nickel plating on aluminium sample.
4.3
Adhesion Analysis
After plating, all samples were subjected to an adhesion test using the knife
test and tape test. Adhesion testing was necessary to ensure the Ni coating is adhered
properly to the aluminium substrates. Based on this simple test, the results showed
that Ni plating produced at current density below 1.0A/cm2 give a better level of
adhesion, compared to the sample produced at current densities above 1.0A/cm2 for
both Watt’s and sulphate based Ni solution. Figure 4.2(a) and Figure 4.2(b) show the
adhesion test results for good and poor adhesion of Ni plating layer on aluminium
substrate respectively.
44
(a) Current density: 0.3A/cm2
(b) Current density; 1.0A/cm2
Figure 4.2: Nickel plated sample for (a) Good Ni adhesion and (b) poor Ni adhesion
on aluminium.
4.4
Morphology Analysis
The morphology of the plated substrates was characterized by Scanning
Electron Microscope (SEM) and Energy Dispersive X-Ray (EDAX). Before
morphology testing was necessary to perform sample preparation on the sample to be
tested in order to remove all the scratches and defects on the sample surface which
can affect the observable process and also lead to confusion while interpreting
morphology of the sample later.. After the morphology of the samples is obtained,
elemental analysis was carried out on a selected number of samples were examined
using Energy Dispersive X-Ray (EDAX). This observation was carried out in order
to determine which elements were present on the samples being observed. Figure 4.3
shows the morphology of cross-section of nickel plating on aluminiun for 55oC at
0.3A/cm2 current density by using Watt’s solution. From the cross-section view taken
by SEM, the result clearly shows that adhesion of Ni plated layer is properly
deposited on aluminium substrate. The EDAX analysis for substrate plated at 55oC
temperature and 0.3A/cm2 current density by Watt’s solution is shown in Figure 4.4.
From EDAX analysis, it is indicated that Ni element is present on the sample. The
graph also show that the Al element are exists on the sample but in a small
percentage around 2.08%.
45
Nickel plating layer
Aluminium Substrate
Figure 4.3: Cross section nickel plated on aluminiun surface morphology under
2000x Magnification.
Ni ~ 97.92%
Al ~ 2.08%
Figure 4.4: The EDAX analysis for 55oC temperature and 0.3A/cm2 current density
by Watt’s solution
In this study, the original deposited Ni plating thickness was determined.
Cross-section samples were prepared after plating process and the thickness of Ni
plated was measured for each sample using SEM. Figure 4.5, 4.6 and 4.7 show
morphology for Watt’s solution while Figure 4.8, 4.9 and 4.10 show morphology for
sulphate based Ni solution at temperature 55oC, 60oC and 65oC respectively, with
different current density.
46
(a)
(b)
(c)
Figure 4.5: Cross-section Ni plated on aluminium surface at 55oC for (a) 0.1A/cm2,
(b) 0.3A/cm2 and (c) 0.6A/cm2 current density.
(a)
(b)
(c)
Figure 4.6: Cross-section Ni plated on aluminium surface at 60oC for (a) 0.1A/cm2,
(b) 0.3A/cm2 and (c) 0.6A/cm2 current density.
47
(a)
(b)
(c)
Figure 4.7: Cross-section Ni plated on aluminium surface at 65oC for (a) 0.1A/cm2,
(b) 0.3A/cm2 and (c) 0.6A/cm2 current density.
(a)
(b)
(c)
Figure 4.8: Cross-section Ni plated on aluminium surface at 55oC for (a) 0.1A/cm2,
(b) 0.3A/cm2 and (c) 0.6A/cm2 current density.
48
(a)
(b)
(c)
Figure 4.9: Cross-section Ni plated on aluminium surface at 60oC for (a) 0.1A/cm2,
(b) 0.3A/cm2 and (c) 0.6A/cm2 current density.
(b)
(a)
(c)
Figure 4.10: Cross-section Ni plated on aluminium surface at 65oC for (a) 0.1A/cm2,
(b) 0.3A/cm2 and (c) 0.6A/cm2 current density.
49
4.5
Effect of Current Density
Nine of aluminium samples were Ni plated sample by using Watt’s solution
and sulphate based Ni solution. After rising with water and drying, the specimen was
weighed using a digital microbalance (four decimal places). The differences in the
weight before and after electrodeposition would be the weight of the plated Ni. The
measured of weight Ni plating layer for Watt’s solution and sulphate based Ni
solution are shown in Table 4.1 and Table 4.2.
(A/cm2)
Density
Current
Table 4.1: Weight of Plated Layer by using Watt’s solution
Weight of Plating Layer (g)
Temperature
55⁰C
60⁰C
65⁰C
0.1
0.0036
0.0048
0.0075
0.3
0.0085
0.0098
0.0132
0.6
0.0146
0.0153
0.0202
(A/cm2)
Current
Table 4.2: Weight of Plated Layer by using sulphate based Ni solution
Weight of Layer (g)
Temperature
55⁰C
60⁰C
65⁰C
0.1
0.0061
0.0073
0.0108
0.3
0.0120
0.0150
0.0185
0.6
0.0189
0.0224
0.0291
By using the data in Table 4.1 and Table 4.2, two graphs has been plotted to
show the weight changes of Ni plated sample with increasing the current density.
The results for weight of Ni plated sample are shown in Figure 4.11 and Figure 4.12.
From both figure, it can be observed that by increasing the current density, the
weight of Ni plated sample had increased.
50
0.025
Weight of Ni plated (g)
0.02
0.015
55⁰C
60⁰C
0.01
65⁰C
0.005
0
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Current Density (A/cm2)
Figure 4.11: Influence of current density on weight of Ni plated layer by using
Watt’s solution
0.035
Weight of Ni plated (g)
0.03
0.025
0.02
55⁰C
60⁰C
0.015
65⁰C
0.01
0.005
0
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Current Density (A/cm2)
Figure 4.12: Influence of current density on weight of Ni plated layer by using
sulphate based Ni solution.
51
According to Faraday’s first law of electrolysis, the amount of a substance
produced or consumed in an electrochemical process depends quantitatively on the
quantity of electricity that flows as the reaction takes place. The amount of electricity
is the product of time and the magnitude of current (Bookrags Staff, 2005). By using
the Faraday’s law equation it can be stated that, for a certain time interval, when the
current applied to the electroplating cell is increased, the amount of metal that is
coated should also increase. However, from the observation it can be seen that the
current density has an affect on the plating adherence and the quality of plating.
When the current density was increased to 1.0 A/cm2 or above the results were poor
level of adhesion. At higher current densities the plated nickel layer were peeling off
very easily from aluminium substrate surface.
4.6
Effect of Temperature
The thickness of the plating nickel for Watt’s solution and sulphate based Ni
solution were calculated from morphology analysis. Table 4.3 and Table 4.4 were
show the measured thickness of nickel plated layers by using Watt’s solution and
sulphate based Ni solution.
Table 4.3: Coating thicknesses by using Watt’s solution
Rate of solution
movement (m/s)
Time (min)
2.7 m/s
4
Influence of temperature on coating thicknesses
Current Density
(A/cm2)
0.1
0.3
0.6
55
Thickness layer
(µm)
3.34
Thickness layer
(µm)
12.00
Thickness layer
(µm)
23.95
60
5.89
14.85
26.00
65
10.65
22.05
34.00
Temperature (oC)
52
Table 4.4: Coating thicknesses by using sulphate based Ni solution
Rate of solution
2.7 m/s
movement (m/s)
4
Time (min)
Influence of temperature on coating thicknesses
Current Density
(A/cm2)
0.1
0.3
0.6
55
Thickness layer
(µm)
6.27
Thickness layer
(µm)
20.65
Thickness layer
(µm)
31.15
60
10.55
25.15
36.20
65
16.35
30.45
43.40
Temperature (oC)
From the data shown in Table 4.3 and Table 4.4, it is observed that for all the
samples, as the temperature was increased from 55oC to 65oC the thickness of nickel
plated layer increased linearly. The relationship between coating thicknesses and
temperature are shown in Figures 4.13 and 4.14. Both figures show that by
increasing the temperature, the thicknesses of Ni plated sample have shown a marked
increase.
40
Coating thivknesses (µm)
35
30
25
55⁰C
20
60⁰C
15
65⁰C
10
5
0
0.1
0.3
0.6
Current Density (A/cm2)
Figure 4.13: Influence of temperature on coating thickness by using Watt’s solution
53
50
45
Coating thivknesses (µm)
40
35
30
55⁰C
25
60⁰C
20
65⁰C
15
10
5
0
0.1
0.3
0.6
Current Density (A/cm2)
Figure 4.14: Influence of temperature on coating thickness by using sulphate based
Ni solution
According to the Misbahul et al., (2002), it is stated that temperature is not a
factor in influencing the weight gain of cathode according to the Faraday’s Law but
it does influence the mobility of ions. Warm electroplating bath increases mobility
and thus lets more metal ions diffuse in and out from electrodes into the
electroplating bath and lowers the overall potential. However, temperature can affect
the amount of plated metal because it affects the rate of the reactions at the
electrodes. In electroplating processes, there is a very small amount of hydrogen gas
production at the cathode, if the electrolyte is an aqueous solution. When the
temperature is increased, the speed of formation of H2 increases more rapidly than
the electrodeposition of metal and at the same time the cathodic efficiency decreases.
Also the dissolution rate of the cathode increases and the decrease of over-potential
hydrogen with the increase of the temperature produce an increase the H2 release
(Barbato et al., 2008). Relying on this factor, it can be stated that the thickness of
deposited metal increases as the temperature is increased.
54
Mibahul et al., (2002) also state that the ideal temperature of electroplating
bath is ranged from 45 oC to 65oC. The electroplated samples, which were produced
at low temperatures i.e. 30oC and 40oC, gave dull appearances whilst samples plated
at higher temperatures 50oC to 70oC gave bright appearances. Finally, gradually dull
and brownish colour appeared when the temperature was increased to 100oC.
Electroplating in an over high temperature that was 100 oC, produced a sticky and
brownish deposit but still possesed acceptable corrosion resistance ability.
4.7
Effect of Type of Solution
In this research, the rate of deposition was calculated. The rate of deposition
of the sample could be calculated using the following equation, 𝐷𝑅 =
𝑇 (𝜇𝑚 )
𝑡 (min )
, where
T and t stand for, thickness and plating time respectively. As discussed in Chapter 3,
two bath solutions were tested in the present works which are Watt’s solution and
sulphate based Ni solution. Table 4.5 shows the rate of deposition for both solutions
with a different temperature and current density. From data in Table 4.5, a graph has
been plotted to show the changes of Ni plated deposition rate for both solution at
different temperature and different current density. From these graphs, it is obvious
that the sulphate based Ni solution give the higher rate of deposition compared to the
Watt’s solution as the current density was increased. From the observations it is
concluded from deposition rate, higher the current densities the higher is the rate of
deposition. The rates of deposition increased because the rate of transferring of
nickel atoms was increased during the plating process and more nickel atoms were
deposited on aluminium surface.
55
Table 4.5: Deposition rate at different type of solution
Temperature
55
Watt’s
Solutions
Solution
0.6
0.3
0.1
Deposition rate (µm/min)
Type of
60
Nickel
Nickel
Watt’s
Sulphate
Sulphate
Solution
Solution
65
Solution
Watt’s
Solution
Sulphate
Solution
1.5675
1.4725
2.5450
2.6625
4.0875
3.0000
5.1625
3.7125
6.2875
5.5125
7.6125
5.9250
7.7875
6.5000
9.0500
8.5000
10.8500
55oC
60oC
65oC
10
8
6
4
2
0
Nickel
0.8350
12
Deposition Rate (µm/min)
Current Density (A/cm2)
(oC)
Watt’s
solution
Sulphate
based Ni
solution
Watt’s
solution
Type of Solution
0.1 A/cm2
Sulphate
based Ni
solution
0.3 A/cm2
Watt’s
solution
Sulphate
based Ni
solution
0.6 A/cm2
Figure 4.15: Influence of different type of solution on deposition rate
56
CHAPTER 5
CONCLUSION
5.1
Conclusion
1.
It has been possible to plate nickel directly on aluminium without any pretreatment process by using high speed electroplating technique.
2.
Very good level of adhesion has been obtained at relatively lower current
densities.
3.
The adhesion test results showed that nickel plating produced at current
density below 1.0A/cm2 gave better level of adhesion, compared to the
sample produced at current density above 1.0A/cm2 for both Watt’s and
sulphate based Ni solution. Nickel plating peeled off easily at current
densities above 1.0A/cm2.
4.
By increasing the current density and temperature, the weight and thicknesses
of Ni plated layer also increased for both solutions.
5.
Sulphate based Ni solution gives higher rate of deposition compare to the
Watt’s solution as the current density and temperature are increased.
57
CHAPTER 6
RECOMMENDATION
6.1
Recommendations
Direct Ni plating on aluminium surface has just been accomplished; however
this has opened up avenues for many improvements that can be accomplished. Thus
based on the experience from this research project, the following recommendation or
suggestions are made for further work;
a)
Study the effect of increasing and decreasing the speed of the electrolyte on
the rate of deposition and microstructure and properties of the Ni deposits.
b)
Further study by comparing effect of current density, temperature and
solution by using the different of material such as titanium or stainless steel.
c)
More parameter needs to be added into the study such as different plating
time, different value of temperature and different type of solution so that
more information can be analyzed and investigated on the sample.
58
REFERENCES
Anynomous (2010). “The Electro Nickel Plating Process [Online]. Thomas
publishing
Company.
Available
at:
http;//www.thomasnet.com/articles/custom-manufacturing
fabricating/
electroplating-process.(Access: 6 November 2010).
Asada, T. (1970). Method of Electroplating Nickel on an Aluminium Article. (U.S
Patent 3, 515, 650).
Barbato, S., Ponce, J., Marcelo, J.L., Jacqueline. C. and Rodrigo, E. (2008).
Study of the Effect of Temperature on the Hardness, Grain Size, and Yield
in Electrodeposition of Chromium on 1045 Steel. J.Chill, Chemistry Soc.,
vol 53, pp 1440-1443
[Online].
Available
at:
http://www.bookrags.com/research/faradays-laws-woc/.
(Access:
6
Bookrags
Staff
(2005).
“Faraday’s
Law”.
November 2010)
Bornhauser, O., Strasbourg and France. (1932). Electroplating of Aluminium.
(U.S Patent 2, 028, 312).
Christopher, W. C (2002). Back to Basics: Electroplating and Electropolishing
of Jewellery. International Technology, World Gold Council London.
Cooper, C.F., Lake, G. and Mich. (1961). Electroplating Process. (U.S Patent 2,
977, 295).
Dennis, J. K and Such, T. E. (1993). Nickel and Chromium Plating.(3rd ed.)
Abington Hall; Woodhead Publishing Ltd.
59
Dibari, G. A. (2000). “Nickel Plating”. International Nickel Inc., Saddle Brook.
pp 224 – 241.
Frasch, J. (1941). Process for Direct Nickel Plating of Aluminium and its Alloys.
(U.S Patent 2, 233, 410).
Gay, R. N. and Wayne, K.R., (1988). Process for Electroplating Nickel over
Stainless Steel. (US Patent 4,764,260).
George, T. and Chadd, K. (2009). “Aluminum/Electroless nickel... a choice
finish”.
Tectmetals,
INC.
[Online].
Available
at:
http://www.techmetals.com/Aluminum-Electroless-Nickel-A-ChoiceFinish.aspx. (Access: 29 March 2010)
Ghorbani, M., Nasirpouri, F., Zad, A. I, and Saedi, A. (2006). “On the Growth
Sequence of Highly Ordered Nanoporous Anodic Aluminium Oxide.”
Material and Design. vol. 27, Issues 10, pp. 983 – 988.
Graves, B. A. (2009). “Nickel Plating Primer” Products Finishing Magazine
[Online]. Available at: http://www.pfonline.com/articles/040102.html.
(Access: 29 March 2010)
Hibbard, G.D., Radmilovic, V., Aust, K.T. and Erb, U. (2008). “Grain Boundary
Migration during Abnormal Grain Growth in Nanocrystalline Ni.”
Materials Science and Engineering. Vol 494, Issues 1-2, pp 232-238.
Hussain, M.S. Patent Pending (2010). “Nanocrystalline Ni Plating Directly on
Aluminium by High Speed Electroforming.”
Hussain, M.S. Direct Electrolytic Ni deposition on non-conductive Al Surfaces
without Any Pre-treatment (To be published).
60
Juhl, A. D. (1999). Theoretical Introduction to Pulse Anodizing. Doctor
Philosophy. AluConsult, Denmark.
Kampert, W. P. and Burell, L. (1976). Metal Plating on Aluminium. (U.S Patent
3, 989, 606).
Kopeliovich,
D.
(2010).
“Nickel
(Substances&Technologies)
Electroplating”
[Online].
Available
http://www.substech.com/dokuwiki/doku.php?id=
SubsTech
at:
nickel
_electroplating&DokuWiki=5dcdca7f7e263a7de3372d0f2880af50#watts
_nickel_plating_solutions. (Access: 29 March 2010).
Krishnam, S. C. and Sanjeeb, K. L (2007). Effect of Substrate Texture on
Electroplating. Bachelor of Technology in Metallurgical and Materials
Engineering. National Institute of Technology, Rourkela.
Le, S. H., Camerlingo, A., Pham, H. T. M., Rejaei, B. and Sarro, P. M. Anodic
Aluminum Oxide Templates for Nanocapacitor Array Fabrication. Delft
University of Technology, Delft Institute of Microelectronics and
Submicrontechnology (DIMES); pp. 96-100.
Li, A. P., Muller, F., Birner, A., Nielsch, K. and Gosele, U. (1998). “Hexagonal
Pore Arrays with a 50 – 420 nm Interpore Distance Formed by Selforganization in Anodic Alumina.” Journal of Applied Physics. vol. 84.
Issues. 11, pp. 6023 – 6026.
Liona, L. V. (2005). “Nickel Electroplating”. Transducers Science and
Technology
[Online].
Available
at:
http://tst.ewi.utwente.nl/research/microfabrication/mmflowcontrollers/ind
ex.html. (Access: 29 March 2010).
Luan, B., Le, T., and Nagata, J. (2004). “An Investigation on the Coating of 3003
aluminium alloys.” Surface and Coating Technology. vol 186, Issues 3,
pp. 431 – 443.
61
Masuda, H., Matsui, Y., Yotsuya, M., Matsumoto, F., and Nishio, K. (2004).
“Fabrication of Highly Ordered Anodic Porous Alumina Using Selforganized Polystyrene Particle Array.” Chemistry Letter. vol. 33. Issues
5. pp. 584 – 585.
Mest, G. T. (2009). “Nickel Electroplating”. Products Finishing Magazine
[Online]. Available at: http://www.pfonline.com/articles/pfdmest01.html.
(Access: 29 March 2010)
Metzger, R. M., Konovalov, V. V., Ming, Sun., Tao, Xu., Zangari, G., Bin, Xu.,
Benakli, M. and Doyle, W. D. (2000). “Magnetic Nanowires in
Hexagonally Ordered Pores of Alumina.” IEEE Transitions on
Magnetics. vol. 36. Issues 1, pp. 30 – 35.
Miller, G. A. (1972). Processes for Nickel Plating Metals. (U.S Patent 3, 667,
991).
Miney, P. G., Colavita, P. E., Schiza, M. V., Priore, R. J., Haibach, F. G. and
Myrick, M. L. (2003). “Growth and Characterization of a Porous
Aluminium Oxide Film Formed on an Electrically Insulating Support.”
Electrochemical and Solid State. vol 6. Issues 10, pp. B42 – B45.
Moller, P. (1994a). Plating on Aluminium. European Aluminium Association
(EAA). Dansk Technisca Hoogschool, Lyngby.
Moller, P. (1994b). Surface Treatment of Aluminium. European Aluminium
Association (EAA). Dansk Technisca Hoogschool, Lyngby
Oliveira, E. M., Finazzi, G. A. and Carlos, I. A. (2006). “ Influence of Glycerol,
Mannitol and Sorbitol on Electrodeposition of Nickel from a Watts Bath
and on the Nickel Film Morphology. Surface and Coating Technology.
vol 200, Issues 20 – 21, pp. 5978 – 5985.
62
Satee, R. and Schaumburg. (1980). Direct Nickel Plating of Aluminium. (U.S
Patent 4, 196, 061).
Schlesinger, M. (2002). “Electroplating.” Electrochemistry Encyclopedia
[Online]. Department of Physics University of Windsor. Available at:
http://electrochem.cwru.edu/encycl/art-e01-electroplat.htm. (Access: 29
March 2010).
Singubara, S. (2003). “Fabrication of Nanomaterials using Porous Alumina
Templates.” Journal of Nanoparticle Research. vol. 5. pp. 17 – 30.
Topelian, P. J. and Newark, N.J. (1958). Electroplating. (U.S. Patent 2, 856,
333).
Tsukamoto, T., Okamura, M. and Kutami, T. (1978). Process for Metal Plating
on Aluminium and Aluminium Alloys. (U.S Patent 4, 115, 211).
Wada, K., Shimohira, T., Yamada, M., and Baba, N. (1986). “Microstructure of
Porous Anodic Oxide Films on Aluminium.” Journal of Material
Science. vol. 21, pp. 3810 – 3816.
Wan, Young Jang. (2005). “Electrical Transport Measurements of Individual
Bismuth Nanowires and Carbon Nanotubes.” The University of Texas at
Austin.