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ELECTROLESS NICKEL
Functional surfaces with electroless nickel
INFORMATION FOR INDUSTRIALISTS I MARKETING SPECIALISTS I TECHNICAL DESIGNERS I MANAGERS AND BUYERS
SURFACE ENGINEERING ASSOCIATION I BRITISH SURFACE TREATMENT SUPPLIERS ASSOCIATION
THE BASIC PROCESS
Depending on solution composition and working
WHAT IS ELECTROLESS NICKEL?
parameters it is possible to deposit nickel
Electroless Nickel process produces a nickel
phosphorous alloy layers with a phosphorous
alloy that can be deposited without an external
content between approximately 2 and 14 % by
power source. The electroless nickel solution
weight.
consists nickel ions, reducing agents, and
other chemicals. The most commonly used
WHICH BASE MATERIAL CAN BE PLATED?
reducing agent is sodium hypophosphite. Nickel
phosphorous alloys can be deposited on to
It is possible to plate almost all metals (steel,
specially activated surfaces, which act as a
stainless steel, aluminium and its alloys, brass etc)
catalyst. The depositing mechanism can be
and non-conductive materials (plastics, ceramics).
simplified as follows:
Each type of material requires a specific
pretreatment. The quality of the electroless nickel
Ni++ + Hypophosphite Ni + Orthophosphite
deposit is dependant upon the quality and surface
The deposited metal layer has the great
finish of the substrate material. In contrast with
advantage of having an even thickness over all
many electroplated nickel coatings the electroless
surfaces of the component virtually regardless of
nickel deposit reproduces the substrate surface
itsshape. This cannot be achieved with electrode
finish.
posited coatings.
NUMEROUS APPLICATIONS:
HOW DOES AN ELECTROLESS
NICKEL SOLUTION WORK?
ENGINEERING
Components made of steel, aluminium and brass
as well as alloys can be protected from corrosive
The parts for electroless nickel plating have to be
and abrasive wear by electroless nickel deposits.
suitably pre-treated. Electroless nickel solutions
It is possible to achieve even deposits and
operate specifically according to their end
specified thickness on complicated shaped
requirements in a pH 4 - 9 medium at a
components providing that the plating solution can
temperature of between 25 – 92oC. The plating
speed of the solution is between 2 – 25 μm/hr
freely circulate in contact with all surfaces.
and the deposit thickness generated on the parts
TEXTILE INDUSTRY
depends upon the operating conditions and time.
The high hardness and abrasion resistance of
heat-treated deposits of electroless nickel and the
ELECTROLYTIC
CHEMICAL ELECTROLESS
use of composite coatings, extend the working life
of parts that are in contact with fast moving textile
products.
AUTOMOTIVE INDUSTRY
There are many applications for electroless
nickel deposits due to their good corrosion and
abrasion resistance. For example the clutch,
nickelplated parts for ABS systems, fuel injector
FIGURE 1 DEPOSIT DISTRIBUTION ON A COMPLICATED SHAPED COMPONENT.
ELECTROLYTICALLY PLATED (LEFT) ELECTROLESS PLATED ( RIGHT)
pumps and injectors.
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SURFACE ENGINEERING ASSOCIATION I BRITISH SURFACE TREATMENT SUPPLIERS ASSOCIATION
OIL AND GAS INDUSTRY
for
The application of electroless nickel deposits in
pipelines and valves have been used successfully
this industry are numerous. The deposits are used
for many years. Components exposed to off shore
as diffusion barriers, as a soldering aid, as
environments demand a very high level
shielding and to enhance corrosion and abrasion
of protection. Electroless nickel layers of about
resistance. Deposits containing more than 10%
Electroless
nickel
plated
ELECTRONICS AND COMPUTER INDUSTRY
components
50 μm on steel have very good resistance to
phosphorus possess no ferromagnetic properties.
marine environments.
These deposits are used as the base for magnetic
memory discs, which have a ferromagnetic
memory top coating.
CHEMICAL INDUSTRY
Electroless nickel coatings are resistant to a wide
range of chemicals, which makes them suitable for
many applications in the chemical industry. For
example, stirrers, valves, reaction tanks, and
covers. In many cases it is possible to use
electroless nickel plated steel as a substitute for
stainless steel.
PAPER INDUSTRY
NUCLEAR INDUSTRY
Electroless nickel plated rolls (cylinders) and
The remarkable properties of electroless nickel
string guides have been used for many years.
coatings enable it to be used in many applications
Compared to hard chromium deposits there is no
in the nuclear industry.
mechanical post treatment required.
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SURFACE ENGINEERING ASSOCIATION I BRITISH SURFACE TREATMENT SUPPLIERS ASSOCIATION
AEROSPACE INDUSTRY
Electroless Nickel finds many applications in this
Electroless nickel deposits with a thickness of
industry also: For example, defrosting valves for
30 -50 m on steel cylinders for support equipment
plane engines, plugs, oil pump cases ad bolts. The
provide excellent resistance even against strong
excellent deposit distribution, good corrosion and
corrosion and abrasive wear.
abrasion properties are the principal reasons for
PLASTICS INDUSTRY
selecting electroless nickel.
Electroless nickel is successfully used in the
plastics industry to maintain and repair tools and
moulds. It is also used as a corrosion protection
layer on surfaces in contact with cooling water.
Electroless nickel is widely used as an undercoat
to improve adhesion of electroplated coatings on
plastic mouldings. For example sanitary bathroom
fittings.
COMPRESSOR, PUMP AND VALVE INDUSTRY
Electroless nickel deposits are very corrosion
and wear resistant as well as being uniformly
distributed. This offers advantages over electroplated nickel deposits.
HYDRAULIC INDUSTRY AND MINING
By using electroless nickel composites on
drilling components it is possible to extend their
working life significantly.
The most important applications in this industry
are the hydraulic units such as drilling and support
equipment.
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SURFACE ENGINEERING ASSOCIATION I BRITISH SURFACE TREATMENT SUPPLIERS ASSOCIATION
DEPOSIT PROPERTIES
HEAT TREATMENT AND ABRASION
RESISTANCE
GENERALLY
The deposit properties of a electroless nickel layer
Electroless Nickel deposits may be heat treated to
and the performance of the plated component
improve abrasion resistance, increase hardness
depend upon its phosphorous content, its purity,
and enhance corrosion. The heat treatment
the substrate, the pretreatment and the thickness.
temperature must be above 240oC. To obtain the
maximum hardness it is necessary to treat at a
STRUCTURE
temperature of 400o C for 1 hour according to the
Nickel phosphorous deposits are homogenous and
attached table. Heat Treatment at different
are generally pore free. They are either micro
temperatures (see chart) achieves hardness of
crystalline or amorphous, which is a form of
about 1000 VPN (HK0.05/HV 0.1).
metallic glass.
By using heat treatment it is possible to enhance
the abrasive wear resistance. The average
CHEMICAL RESISTANCE AND
coefficient of friction is about 0.3 and can be much
CORROSION PROTECTION
smaller in certain cases (0.03).
Electroless nickel deposits are resistant against
most organic and inorganic chemicals apart from
oxidising acids. The resistance is especially good
in neutral and alkaline solutions. With a protective
layer of 25 μm on steel or aluminium it is possible
to achieve many years lasting protection even
against
aggressive
industrial
and
marine
conditions. There are recommended deposits
thicknesses for specific corrosive conditions.
MECHANICAL PROPERTIES
Electroless nickel deposits can be plated either
with a tensile or compressive stress. The micro
hardness of these layers is between 500 to 700
Vickers Pyramid Number. The ductility is between
0.1 and 2% depending on the type of deposit.
COMPOSITE DEPOSITS
Electroless nickel layers can also be co-deposited
with different inclusions for many applications
particularly to give improved abrasion resistance.
For example: Electroless nickel + silicon carbide,
PTFE or diamond.
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SURFACE ENGINEERING ASSOCIATION I BRITISH SURFACE TREATMENT SUPPLIERS ASSOCIATION
COMMUNICATION
Modern process control facilities can document
this to the latest ISO standards including deposit
The customer and the plater have to co-operate
thickness, brightness and surface roughness.
in order to obtain the desired qualities.
To meet service requirements a detailed
PLATING PLANT TECHNOLOGY
specification must be agreed. It is necessary to
exchange information on the following topics.
Application of the Electroless Nickel plated
component.
Substrate and its composition before the
application of Electroless Nickel.
Today’s plating plant technology is able to
produce consistently high quality Electroless Nickel
deposits. Almost any parameter or variable such
as deposition times etc, are easily computer
controlled and documented automatically.
Is any heat treatment to be used after plating?
Process in plant technology also benefits the
Thickness of the Electroless Nickel layer desired.
environment. Modern Electroless Nickel plants can
Every Surface coating has its optimal application
be designed to recycle all used rinse water
conditions, particularly Electroless Nickel.
completely eliminating discharge of liquid
effluent.
QUALITY CONTROL
In order to produce Electroless Nickel layers of
constant quality, the composition of the electrolyte
has to be checked regularly.
Strict controlled process parameters are the
guarantee of good adhesion, wear resistance and
temperature resistance of deposits.
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THE SURFACE
Electroless Nickel plated surfaces are safe in terms
of health and safety requirements.
SURFACE ENGINEERING ASSOCIATION I BRITISH SURFACE TREATMENT SUPPLIERS ASSOCIATION
“The Electroless deposition of Nickel was first developed by Brenner & Riddell in 1946. Since then
the process technology has improved substantially and the process is well established in many
industrial areas. However the basics of the original chemistry have seen limited change until the
last two decades. In response to increasing Environmental and Legislative pressures, greater
attention has been given to waste minimisation and the use of more environmentally friendly
chemistry and techniques.
The introduction of the End Of Life (ELV) legislation and the Waste Electrical and Electronic
Equipment (WEEE) directive seek to eliminate any materials or deposits that will not allow easy
and acceptable recycling of components in the Automotive and Electronics industries.
ELV compliant processes are now readily available to allow applications within the Automotive
and Electronics industries to be fulfilled eliminating the co-deposition of unacceptable elements,
thus allowing the safe recycling of Electroless Nickel plated components at the end of their useful
life. Longer-life chemistries based upon alternative Nickel compounds to the traditional Nickel
Sulphate versions can extend the working life of the plating bath by a factor of tow or more. The
use of membrane technology – Electro dialysis – to extend the life of more traditional formulations
by thecontinuous removal of undesirable by products has now been used very successfully for
over 10 years now. Such techniques are already helping to reduce waste considerably, by extending
the plating bath life almost indefinitely.
Details of suppliers of these advanced technologies and/or of any Electroless Nickel technology
can be obtained from the British Surface Treatment Suppliers Association.”
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SURFACE ENGINEERING ASSOCIATION I BRITISH SURFACE TREATMENT SUPPLIERS ASSOCIATION
The Surface Engineering Association is the
The British Surface Treatment Suppliers Association
umbrella organisation for the advancement of the
is dedicated to the promotion and continuous
surface engineering industry and its members
improvement of the surface treatment industry
span the whole of the industry sector.
to the mutual benefit of its members and the
customers they serve. Members are committed to
upholding the highest standards of quality. Health,
safety and environmental protection.
Published in the interests of the surface finishing
industry by the British Surface Treatment Suppliers
Association. A member of the Surface Engineering
Association.
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Surface Engineering Association