U.S. patent application number 11/576177 was filed with the patent office on 2008-08-21 for non-galvanically applied nickel alloy.
This patent application is currently assigned to AHC OBERFLACHENTECHNIK GMBH & CO. OHG. Invention is credited to Doris Bialkowski, Alfons Hollander.
Application Number | 20080196625 11/576177 |
Document ID | / |
Family ID | 35613047 |
Filed Date | 2008-08-21 |
United States Patent
Application |
20080196625 |
Kind Code |
A1 |
Bialkowski; Doris ; et
al. |
August 21, 2008 |
Non-Galvanically Applied Nickel Alloy
Abstract
Lead-free nickel phosphorus dispersion alloy present on a
metallic substrate surface, obtainable by electroless deposition in
an electrolyte which contains 4 to 7 g/l of nickel ions; 15 to 40
g/l of hypophosphite; at least one stabiliser; 5 to 400 mg/l of an
alkylaryl oxydialkyl benzyl ammonium chloride or a partially
fluorinated betaine; 50 to 60 g/l of a carboxylic acid-containing
complexing agent A; 5 to 40 g/l of a carboxylic acid-containing
complexing agent B different from A; 4 to 10 g/l of dispersed
particles which differ from the composition of the
nickel/phosphorus alloy; and contains no boric acid or borates, and
articles coated therewith.
Inventors: |
Bialkowski; Doris;
(Weilerswist, DE) ; Hollander; Alfons;
(Kerpen-Buir, DE) |
Correspondence
Address: |
OCCHIUTI ROHLICEK & TSAO, LLP
10 FAWCETT STREET
CAMBRIDGE
MA
02138
US
|
Assignee: |
AHC OBERFLACHENTECHNIK GMBH &
CO. OHG
Kerpen
DE
|
Family ID: |
35613047 |
Appl. No.: |
11/576177 |
Filed: |
September 26, 2005 |
PCT Filed: |
September 26, 2005 |
PCT NO: |
PCT/IB2005/053173 |
371 Date: |
January 10, 2008 |
Current U.S.
Class: |
106/287.18 |
Current CPC
Class: |
C23C 18/36 20130101;
C23C 18/50 20130101; C23C 18/1662 20130101 |
Class at
Publication: |
106/287.18 |
International
Class: |
C23C 18/36 20060101
C23C018/36 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 28, 2004 |
DE |
102004047423.0 |
Claims
1. Lead-free nickel phosphorus dispersion alloy present on a
metallic substrate surface, obtainable by electroless deposition m
an electrolyte containing 4 to 7 g/l of nickel ions; 15 to 40 g/l
of hypophosphite; at least one stabiliser; 5 to 400 mg/l of an
alkylaryl oxydialkyl benzyl ammonium chloride or a partially
fluorinated betaine; 50 to 60 g/l of a complexing agent A
containing carboxylic acid; 5 to 40 g/l of a complexing agent B
different from A containing carboxylic acid; 4 to 10 g/l of
dispersed particles which differ from the composition of the
nickel/phosphorus alloy; and no boric acid or borates the data
relating to the composition of the electrolyte as a whole.
2. Nickel alloy according to claim 1 characterised in that the
electrolyte contains, as stabiliser, at least 10 mg/l of antimony
ions and maximum 1.5 mg/l of bismuth ions.
3. Nickel alloy according to claim 2 characterised in that the
electrolyte contains, as stabiliser, 10-150 mg/l of antimony ions
and 0.01-0.5 mg/l of bismuth ions.
4. Nickel alloy according to claim 1 characterised in that the
electrolyte additionally contains a non-ionic surfactant.
5. Nickel alloy according to claim 4 characterised in that the
non-ionic surfactant is selected from the group of partially
fluorinated or non-fluorinated surfactants.
6. Nickel alloy according to claim 1 characterised in that the
particles are selected from, the group of silicon carbide,
corundum, diamond, cubic boron nitride, spherical aluminium oxide
and boron tetracarbide.
7. Nickel alloy according to claim 1 characterised in that the
particles are non-metallic and exhibit a hardness of more than
1,000 HV.
8. Nickel alloy according to claim 1 characterised in that the
particles exhibit friction-reducing properties and are selected
from the group of polytetrafluoroethylene, molybdenum, sulphide,
molybdenum disulphide, hexagonal boron nitride, tin sulphide and
graphite.
9. Use of a nickel alloy according to claim 1 as wear-resistant
surface, in particular in the motor vehicle industry and in
engineering, particularly preferably as parts of locks for door
closure systems and functional components for fuel metering systems
or as surface in the motor vehicle industry with improved sliding
friction properties, in particular for parts of locks, valves,
rotary ducts, valve anchors, moveable pistons and other moveable
parts in the motor vehicle industry and in engineering.
10. Nickel alloy according to claim 2 characterised in that the
particles exhibit friction-reducing properties and are selected
from the group of polytetrafluoroethylene, molybdenum sulphide,
molybdenum, disulphide, hexagonal boron nitride, tin sulphide and
graphite.
11. Nickel alloy according to claim 3 characterised in that the
particles exhibit friction-reducing properties and are selected
from the group of polytetrafluoroethylene, molybdenum sulphide,
molybdenum disulphide, hexagonal boron nitride, tin, sulphide and
graphite.
12. Nickel alloy according to claim 4 characterised in that the
particles exhibit friction-reducing properties and are selected
from the group of polytetrafluoroethylene, molybdenum sulphide,
molybdenum disulphide, hexagonal boron nitride, tin sulphide and
graphite.
13. Nickel alloy according to claim 5 characterised in that the
particles exhibit friction-reducing properties and are selected
from the group of polytetrafluoroethylene, molybdenum sulphide,
molybdenum disulphide, hexagonal boron nitride, tin sulphide and
graphite.
14. Nickel alloy according to claim 6 characterised in that the
particles exhibit friction-reducing properties and are selected
from the group of polytetrafluoroethylene, molybdenum sulphide,
molybdenum disulphide, hexagonal boron nitride, tin sulphide and
graphite.
15. Use of a nickel alloy according to claim 2 as wear-resistant
surface, in particular in the motor vehicle industry and in
engineering, particularly preferably as parts of locks for door
closure systems and functional components for fuel metering systems
or as surface in the motor vehicle industry with improved sliding
friction properties, in particular for parts of locks, valves,
rotary ducts, valve anchors, moveable pistons and other moveable
parts in the motor vehicle industry and in engineering.
16. Use of a nickel alloy according to claim 3 as wear-resistant
surface, in particular in the motor vehicle industry and in
engineering, particularly preferably as parts of locks for door
closure systems and functional components for fuel metering,
systems or as surface in the motor vehicle industry with improved
sliding friction properties, in particular for parts of locks,
valves, rotary ducts, valve anchors, moveable pistons and other
moveable parts in the motor vehicle industry and in
engineering.
17. Use of a nickel alloy according to claim 4 as wear-resistant
surface, in particular in the motor vehicle industry and in
engineering, particularly preferably as parts of locks for door
closure systems and functional components for fuel metering systems
or as surface in the motor vehicle industry with improved sliding
friction properties, in particular for parts of locks, valves,
rotary ducts, valve anchors, moveable pistons and other moveable
parts in the motor vehicle industry and in engineering.
18. Use of a nickel alloy according to claim 5 as wear-resistant
surface, in particular in the motor vehicle industry and in
engineering, particularly preferably as parts of locks for door
closure systems and functional components for fuel metering systems
or as surface in the motor vehicle industry with improved sliding
friction properties, in particular for parts of locks, valves,
rotary duets, valve anchors, moveable pistons and other moveable
parts in the motor vehicle industry and in engineering.
19. Use of a nickel alloy according to claim 6 as wear-resistant
surface, in particular in the motor vehicle industry and in
engineering, particularly preferably as parts of locks for door
closure systems and functional components for fuel metering systems
or as surface in the motor vehicle industry with improved sliding
friction properties, in particular for parts of locks, valves,
rotary ducts, valve anchors, moveable pistons and other moveable
parts in the motor vehicle industry and in engineering.
20. Use of a nickel alloy according to claim 7 as wear-resistant
surface, in particular in the motor vehicle industry and in
engineering, particularly preferably as parts of locks for door
closure systems and functional components for feel metering systems
or as surface in the motor vehicle industry with improved sliding
friction properties, in particular for parts of locks, valves,
rotary duels, valve anchors, moveable pistons and other moveable
parts in the motor vehicle industry and in engineering.
21. Use of a nickel alloy according to claim 8 as wear-resistant
surface, in particular in the motor vehicle industry and in
engineering, particularly preferably as parts of locks for door
closure systems and functional components for fuel metering systems
or as surface in the motor vehicle industry with improved sliding
friction properties, in particular for parts of locks, valves,
rotary ducts, valve anchors, moveable pistons and other moveable
parts in the motor vehicle industry and in engineering.
Description
[0001] The present invention relates to a lead-free nickel alloy
produced chemically, i.e. electroless, with inclusions as well as
to objects coated therewith.
[0002] Chemical nickel plating of metal surfaces is a process used
frequently on an industrial scale to protect metals against
corrosion and wear.
[0003] In general, a distinction is made between an electrolytic
and an electroless deposition for the production of a nickel
layer.
[0004] Electrolytic deposition--also known as galvanic deposition
or coating--is a deposition reaction on the surface to be coated,
which is brought about by the current introduced.
[0005] In the case of electroless deposition--also known as
chemical deposition or coating--the formation of the layer is based
on an autocatalysed process which is determined decisively by the
electrochemical potentials of the reactants involved.
[0006] An electrolytic process for the production of a nickel layer
is known e.g. from EP 0 218 845 A1 in which an electroplating tank
is used which, apart from a cationic surfactant from the group of
alkylaryl oxydialkyl benzyl ammonium chlorides, necessarily
contains boric acid or borates.
[0007] These layers thus obtained have the disadvantage that they
exhibit a more than proportional layer build-up at the edges and a
less than proportional layer build-up at indentations or undercuts.
For this reason, these processes are not suitable for geometrically
complex structural parts (carburettor bodies, fuel distributors for
injection systems etc., for example) in which an even layer
build-up in all areas is of decisive importance.
[0008] Also, it is not possible to coat such geometrically complex
structural parts on the inside without the use of infernal anodes.
The use of internal anodes has the disadvantage of extremely
difficult positioning; bores with a small diameter (less than 2 mm)
cannot be coated by such processes using an internal anode).
[0009] Consequently, electroless processes have achieved greater
industrial importance in the manufacture of functional (i.e. not
exclusively decorative) nickel layers and/or nickel alloy layers.
In order to achieve an improved protection against corrosion, ii
has proved necessary, to achieve a nickel/phosphorus alloy by
adding suitable compounds to the aqueous electrolyte.
[0010] Pure nickel and phosphinate-containing electrolytes for
chemical nickel plating require additional stabilisers to prevent
spontaneous decomposition. Stabilisation adequate for industrial
application has previously been achieved mainly by the addition of
lead compounds. Stabilisers previously added as an alternative such
as e.g. molybdenum compounds, cadmium or tin compounds exhibit a
reduced effectiveness in comparison with lead.
[0011] Moreover, the addition of lead and cadmium is no longer
acceptable from the points of view of environmental policy; against
this background, it is understandable that the motor vehicle
industry, for example, is no longer permitted to use
lead-containing structural parts in view of the EU end-of-life
vehicles directive in force at present.
[0012] An example of such a bath containing lead in principle for
electroless nickel deposition is described in patent specification
DE 34 21 646 C2. Apart from a metal salt of the above-mentioned
type, a special sulphonium betaine is used as additional
stabiliser.
[0013] According to WO 02/34964, an electrolyte is used for the
production of a lead-free nickel alloy by means of an electroless
process, which electrolyte does not contain any lead-containing
stabiliser but a combination of an antimony compound and a bismuth
compound.
[0014] This specially matched electrolyte is not suitable for the
production of dispersion layers, in particular not of
PTFE-containing nickel layers.
[0015] Such a necessary combination of antimony ions and bismuth
ions in the electrolyte, however, is not universally suitable to
stabilise electrolytes for the production of dispersion coatings.
The production of PTFE-containing dispersion electrolytes with a
combination of an antimony compound and a bismuth compound, in
particular, leads to an unsatisfactory stability of the
electrolyte. The disadvantage here is the fact that the bath
becomes excessively stabilised after a short period.
[0016] Such nickel dispersion layers, however, are being
increasingly used in high performance structural parts such as
parts of locks, valves, rotary ducts, valve anchors, moveable
pistons, complex geometrical fuel conducting parts in the motor
vehicle industry.
[0017] Involved in this case is the deposition of a metal layer by
an electroless process with simultaneous inclusion of solids which
are present in the electrolyte in the dispersed form.
[0018] Depending on the application, these solids are slip
additives (e.g. PTFE, graphite, spherical aluminium oxide,
encapsulated MoS.sub.2 etc.) or hard materials (diamond, corundum,
cubic BN etc.)
[0019] A serious problem during the manufacture of these layers is
posed by the regular incorporation of the solids into the metal
matrix. Non-homogeneous dispersion layers lead to premature and/or
undesirable local wear and tear which, depending on the field of
application, may present a considerable safety risk (e.g. hydraulic
cylinders in the aircraft industry).
[0020] One possibility for manufacturing such a nickel dispersion
layer is described in U.S. Pat. No. 4,997,688 A1. It involves a
process for electroless nickel coating in which an electrolyte is
used which, apart from the nickel cations and phosphinate anions,
contains a mixture of a non-anionic surfactant with a cationic,
anionic or amphoteric surfactant.
[0021] The addition of this combination of surfactants to the
hypophosphite-containing electrolytes has the disadvantage that the
useful life of the electrolyte is dramatically shortened, for
example in the case of the incorporation of finely divided PTFE.
This reduction of the useful life is attributable, among other
things, to the formation of orthophosphite or nickel phosphite
crystals and the formation of decomposition products of the
surfactant mixture added Moreover, a decomposition of the bath can
be observed, depending on the test conditions.
[0022] In addition, the nature of the surface is uneven which
promotes the early abrasion of these dispersion layers.
[0023] Moreover, these nickel dispersion layers are produced using
convention nickel/phosphorus electrolytes which contain either lead
or a combination of fin with cadmium as stabiliser.
[0024] For this reason, there have been increased efforts in the
recent past not to use emulsifiers or surface-active substances in
hypophosphite-containing electrolytes for electroless nickel
plating of PTFE-containing dispersion layers.
[0025] From U.S. Pat. No. 6,273,943, an electrolyte for the
electroless deposition of a nickel/PTFE dispersion layers is known
which exhibits a quaternary perfluoroalkyl ammonium halide and a
lead compound as stabiliser.
[0026] Apart from the decisive disadvantage of the necessary use of
lead, perfluoroctyl sulphonyl (PFOS), an extremely toxic and
bioaccumulative compound, is formed as intermediate product during
the production of perfluoroalkyl ammonium halides.
[0027] The object of the present invention is the provision of a
lead-free nickel/phosphorus dispersion coating present on a
metallic substrate surface, which coating permits a homogeneous
layer build-up (in particular at the edges, in indentations and
undercuts) even on geometrically complex structural parts with
functional inclusions.
[0028] In this connection, as homogeneous an incorporation of the
particles into the nickel alloy matrix as possible is to be
guaranteed.
[0029] This coating is to be suitable in particular for
geometrically complex structural parts which can be subjected to
high mechanical and friction stresses and, moreover, exhibit low
tolerances.
[0030] Finally, these nickel alloy layers should be obtainable by
electroless deposition in an electrolyte which is characterised by
comparatively long useful lives.
[0031] This object is achieved according to the invention by way of
a lead-free nickel/phosphorus dispersion alloy present on a
metallic substrate surface, obtainable by electroless deposition in
an electrolyte containing [0032] 4 to 7 g/l of nickel ions; [0033]
15 to 40 g/l of hypophosphite; [0034] at least one stabiliser;
[0035] 5 to 400 mg/l of an alkylaryl oxydialkyl benzyl ammonium
chloride or a partially fluorinated betaine; [0036] 50 to 60 g/l of
a complexing agent A containing carboxylic acid; [0037] 5 to 40 g/l
of a complexing agent B different from A (e.g. or preferably
dicarboxylic acid); [0038] 3 to 10 g/l of dispersed particles which
differ from the composition of the nickel/phosphorus alloy; and
[0039] no boric acid or borates the data relating to the
composition of the electrolyte as a whole.
[0040] in this respect, it should be noted that the electrolyte
does not contain cadmium either.
[0041] By means of the lead-free nickel/phosphorus dispersion alloy
according to the invention, it is possible for the first time to
provide geometrically complex structural parts such as e.g.
carburettor bodies, fuel distributors for infection systems etc
with a homogeneous layer build-up of a coating that can be
subjected to a high level of friction, in particular at the edges,
in indentations and undercuts.
[0042] in their fully coated state, these structural parts have a
tolerance of .+-.3 .mu.m with a total layer thickness of 10-12
.mu.m.
[0043] Depending on the particles used, it is possible to achieve a
roughness depth and/or functional surface characteristics which are
specifically matched to the corresponding application.
[0044] As a result of the components necessarily present in the
electrolyte in line with the main claim for the production of the
coating according to the invention, a homogeneous incorporation of
the particles info the nickel alloy matrix is guaranteed. In this
way, a wide variety of particle forms, e.g. agglomerates,
individual particles or particles of different geometries, can be
distributed homogeneously, something that can he easily depicted
by- way of a metallographic micrograph.
[0045] Finally, the useful life of the electrolyte used for the
electroless deposition of a dispersion layer according to the
invention having incorporated silicon carbide particles may be a
useful life of up to 10 MTO (metal turn over--i.e. metal throughput
based on the electrolyte used, in litres).
[0046] The term "metallic substrate surface" should be understood
to mean also synthetic resin surfaces which are activated first of
all by means of processes known to the expert and subsequently
nickel plated.
[0047] Metallised synthetic resin surfaces which are produced using
a mechanical microstructurisation are particularly preferred and
disclosed in WO 2004/092436 A2 and WO 2004/092256 A1, for
example.
[0048] A common layer thickness of this nickel/phosphorus
dispersion alloy of between 3 and 30 .mu.m is sufficient to
increase the abrasion resistance, to improve the sliding and
friction properties and to provide anti-adhesion properties.
Depending on the type of particles used, energy transferring
functional layers can also be produced.
[0049] A preferred embodiment of the nickel/phosphorus dispersion
alloy according to the invention is achieved if the components of
nickel, phosphorus and panicles are evenly distributed in the alloy
layer.
[0050] The term "evenly" means here and subsequently a distribution
typical of the alloy and function of the corresponding components
in the nickel matrix. By way of this homogeneous distribution, a
uniform structure is achieved in the alloy such that the mechanical
and functional properties of this layer are constant even within
narrow tolerance ranges.
[0051] The carboxylic and dicarboxylic acids known for the
production of the usual nickel/phosphorus electrolytes are used as
complexing agents A.
[0052] Lactic acid and malonic acid are particularly preferred as
complexing agent A; succinic acid is preferably used as complexing
agent B.
[0053] A simple example of an alkylaryl oxydialkyl benzyl ammonium
chloride is benzalkonium chloride with the formula
##STR00001##
or the formula
##STR00002##
in which X represents a chlorine atom. Such compounds are sold by
Clariant, for example, under the trade name of HYAMIN.RTM.
1622.
[0054] Further simple examples of alkylaryl oxydialkyl benzyl
ammonium chlorides are benzalkonium chloride
(N-alky-N,N-dimethyl-N-benzyl ammonium chloride with a C.sub.12
C.sub.14 or C.sub.16-alkyl radical) and methyl dodecyl benzyl
trimethyl ammonium chloride. Benzalkonium chlorides are sold by
Clariant, for example, under the trade name of HYAMIN.RTM.
3500.
[0055] Those compounds can be used as possible partially
fluorinated betaine, for example; which are sold by Clariant under
the trade name of FLUOWET.RTM. CA.
[0056] In a preferred embodiment of the invention, the electrolyte
contains; as stabiliser; at least 10 mg/l of antimony ions and
maximum 1.5 mg/l of bismuth ions.
[0057] This addition of antimony and bismuth, however, is not
essential--it is thus possible to use only stabilisers based on tin
(II) compounds, for example.
[0058] Particularly preferably, the electrolyte contains, as
stabiliser, 10-150 mg/l of antimony ions and 0.01-1.5 mg/l of
bismuth ions,.
[0059] By selecting the stabilisers according to this embodiment,
it is possible to achieve very high levels of storage stability of
the electrolyte. For an electrolyte with SiC as particles, it is
possible by way of this choice to achieve useful lives of up to 10
MTO (metal turn over--i.e. metal throughput based on the
electrolyte used, in litres) and it is possible to achieved useful
lives of 3 MTO and more for an electrolyte for the production of a
nickel phosphorus-PTFE dispersion layer.
[0060] According to a further embodiment of the present invention,
the electrolyte additionally contains a non-ionic surfactant. The
non-ionic surfactant selected from the group of partially
fluorinated or non-fluorinated surfactants is particularly
preferred. The term "partially fluorinated surfactants" should he
understood to mean ail surface-active substances not exhibiting
perfluorinated radicals. The term "non-fluorinated surfactants"
should be understood to mean all surface-active substances not
exhibiting fluorine atoms.
[0061] In this way, it is possible to obtain an improved, (i.e.
more homogeneous) nickel phosphorus dispersion layer since the use
of an additional non-ionic surfactant contributes to preventing an
undesirable agglomeration in the electrolyte and simultaneously
makes a contribution to keeping the non-soluble components of the
electrolyte in suspension.
[0062] Thus, a longer useful life of the electrolyte is guaranteed
by this embodiment.
[0063] The dispersed particles may be selected in a preferred
embodiment of the present invention from the group of silicon
carbide, corundum, diamond, cubic boron nitride, spherical
aluminium oxide and boron tetracarbide, those particles being
particularly preferred which are non-metallic and have a hardness
of more than 1,000 HV.
[0064] The nickel phosphorus dispersion alloys obtained according
to this preferred embodiment are particularly suitable for
providing the coated substrates with resistance to abrasion,
protection resistance to wear and increased friction to guarantee
tight-fitting connections or the desired surface structure. In this
way, the substrate can be provided with functional properties which
are precisely matched to the requirements of its application. Thus
rough surface structures with typical functional inclusions are
achieved in the case of a nickel phosphorus dispersion layer with
incorporated silicon carbide particles, which, in tight fitting
connections, achieve friction values of .mu.=0.50 and more (for
comparison; the friction value in a dry steel contact amounts to
only .mu.=0.15).
[0065] In another, also preferred, embodiment, the particles
exhibit friction-reducing properties and are selected from the
group of polytetrafluoroethylene, molybdenum sulphide, molybdenum
disulphide, hexagonal boron nitride, tin sulphide and graphite.
[0066] The nickel phosphorus dispersion layers obtainable according
to this embodiment must also be selected according to the
functional requirements of the resulting structural part. Thus,
excellent friction-reducing properties are achieved by
incorporating PTFE particles into the nickel phosphorus matrix.
Only by way of this special composition of the electrolyte
according to the present invention is it possible to provide a
lead-free and cadmium-free system which guarantees a stability
sufficient also for the production of nickel phosphorus PTFE alloys
and good surface properties. As a result of the complex interaction
of all the components involved regarding the stability of the
electrolyte and good deposition rates, it had previously not been
known to provide electrolytes containing polytetrafluoroethylene
which do not depend on lead-containing or cadmium-containing
stabilisers.
[0067] A further advantage of the embodiment according to the
invention is the fact perfluorinated cationic or non-ionic
surfactants are dispensed with. For electrolytes containing
polytetrafluoroethylene, in particular, perfluorinated cationic and
non-ionic surfactants had previously been mainly used since these
alone had been suitable to provide the PTFE particles with the
charge necessary for migration and co-deposition. The production of
these fluorinated cationic and non-ionic surfactants, however,
takes place via a toxic intermediate stage "perfluorooctyl
sulphonyl") with a bioaccumulation potential such that these have
been removed by manufacturers from their production programme
worldwide. This development has led to a search for new methods in
order to be able to continue produce PTFE-containing nickel
phosphorus dispersion alloys without having to use the
fluorine-containing cationic surfactants no longer available. It is
precisely this application, however, which is possible with a
nickel phosphorus PTFE dispersion alloy of the present invention in
a manner which takes into account all framework conditions imposed
by environmental and health policies.
[0068] The nickel phosphorus dispersion alloys according to the
present invention can he used as wear-resistant surface, in
particular in the motor vehicle industry and in engineering,
particularly preferably as parts of locks for door closure systems
and functional components for fuel metering systems or as surface
in the motor vehicle industry with improved sliding friction
properties, in particular for parts of locks, valves, rotary ducts,
valve anchors, moveable pistons and other moveable parts in the
motor vehicle industry and in engineering.
[0069] The individual process steps for the production of a
chemically produced nickel alloy by electroless metal deposition in
an aqueous electrolyte are known in principle. This applies in
particular to selecting suitable compounds for the nickel cations
and phosphinate ions. In addition, it is known to the expert which
additives, stabilisers, complexing agents or other additives are
additionally necessary for a corresponding nickel alloy.
[0070] However, these parameters are not critical for the
application of the process according to the invention. For this
reason, this basic knowledge is not dwelled on in detail, instead
reference should be made to the textbook "Einfuhrung in die
Galvanotechnik (Introduction into electroplating technology) by
Bernhard Gaida, E. Leuze Verlag.
[0071] in the process according to the invention, the proportion of
nickel cations in the electrolyte may amount to 4 to 7 g/l, based
on the sum total of the components of nickel and phosphorus present
in the aqueous electrolyte.
[0072] The proportion of phosphinate ions in the electrolyte may be
between 15 and 40 g/l, based on the weight ratio of phosphorus to
the sum total of the components of nickel and phosphorus present in
the aqueous electrolyte.
[0073] The proportion of alkylaryl oxydialkyl benzyl ammonium in
the electrolyte may be between 0.01 and 0.4% by weight, in
particular between 0.1 and 0.2% by weight, based on the sum total
of the components of nickel and phosphorus present in the aqueous
electrolyte.
[0074] The sum total of the proportions described above of the
components present in the electrolyte is usually 100% by
weight.
[0075] The following examples serve to illustrate the
invention:
[0076] Test methods:
[0077] The determination of the useful life (in
MTO=metal-turn-over) takes place via wet chemical titration on a
murexid indicator as consumption in g/l of nickel.
[0078] The value is calculated from the quantity of nickel ions
which can be added to the finished electrolyte without the
electrolyte having to be replaced. It is based on the total
quantify of nickel in the electrolyte bath.
[0079] The determination of the homogeneous distribution of the
PTFE particles takes place via a metallographic micrograph of the
coated steel sheet. It is characterised by determining the
percentage proportion of the distribution of the particles
incorporated into the nickel/phosphorus matrix.
EXAMPLE 1
[0080] (Comparative Example):
[0081] Into a 1 l glass beaker, 500 ml of fully demineralised water
are introduced and the following compounds are added with stirring:
[0082] 30 g/l of nickel sulphate ((NiSO.sub.4.times.6H.sub.2O)
[0083] 35 g/l of sodium phosphinate
(NaH.sub.2PO.sub.2.times.H.sub.2O) [0084] 30 g/l of malonic acid
[0085] 30 g/l of succinic acid [0086] 0.5 mg/l of bismuth methane
sulphonate (Bi(OS(Of).sub.2CH.sub.3).sub.3) [0087] 1.5 g/l of
antimony chloride [0088] 10 ml/l of tetrafluoroboric acid (50%)
[0089] 100 mg/l of allyl thiourea [0090] 370 mg/l of cationic
perfluorinated fluorine surfactant "FT 754" from 3M [0091] 7 g/l of
PTFE dispersion Zonyl.RTM. 3807 from DuPont [0092] 15 mg/l of
non-ionic surfactant "FSN-100" from DuPont
[0093] Subsequently, the pH is adjusted to 4.3 by adding a 25%
aqueous ammonia solution and the solution is made up to 1000 ml by
adding fully demineralised water.
[0094] After heating to 88.degree. C., steel panels, 1 mm thick, of
the alloy St 37 with the dimension 50.times.50 mm are suspended
following the usual pretreatment (degreasing, rinsing, activating,
rinsing) for 60 minutes in the bath.
[0095] Subsequently, the sheet metal is rinsed and dried. The layer
thickness achieved is 5 .mu.m.
[0096] The results of the useful life of the electrolyte and the
PTFE distribution in the dispersion layer are determined according
to the test methods described above and are given in Table I.
EXAMPLE 2
[0097] (According to the Invention):
[0098] Comparative example 1 is repeated, though with the following
electrolyte composition: [0099] 25 g/l of nickel sulphate
((NiSO.sub.4.times.6H.sub.2O) [0100] 35 g/l of sodium phosphinate
(NaH.sub.2PO.sub.2.times.H.sub.2O) [0101] 30 g/l of lactic acid
(synthetic) [0102] 30 g/l of succinic acid [0103] 0.5 mg/l of
bismuth tartrate [0104] 1.5 g/l of antimony chloride [0105] 0.5
mg/l of potassium o-ethyl dithiocarbonate [0106] 195 mg/l of
Hyamin.RTM. 1622 from Lonza [0107] 7 g/l of PTFE dispersion
Zonyl.RTM. 3807 from DuPont [0108] 15 mg/l of non-ionic surfactant
"FSN-100" from DuPont
[0109] The pH of the electrolyte is adjusted to 4.5 by adding a 25%
aqueous ammonia solution. The layer thickness achieved is 5
.mu.m.
EXAMPLE 3
[0110] (According to the Invention): [0111] 25 g/l of nickel
sulphate ((NiSO.sub.4.times.6H.sub.2O) [0112] 35 g/l of sodium
phosphinate (NaH.sub.2PO.sub.2.times.H.sub.2O) [0113] 35 g/l of
lactic acid (synthetic) [0114] 30 g/l of succinic acid [0115] 0.5
mg/l of bismuth tartrate [0116] 1.5 g/l of antimony chloride [0117]
0.5 mg/l of potassium o-ethyl dithiocarbonate [0118] 725 mg/l of
Fluowet.RTM. CA from Clariant [0119] 7 g/l of PTFE dispersion
Zonyl.RTM. 3807 from DuPont [0120] 15 mg/l of non-ionic surfactant
"FSN-100" from DuPont
[0121] The layer thickness achieved is 5 .mu.m.
EXAMPLE 4
[0122] (According to the Invention): [0123] 30 g/l of nickel
sulphate ((NISO.sub.4.times.6H.sub.2O) [0124] 40 g/l of sodium
phosphinate (NaH.sub.2PO.sub.2.times.H.sub.2O) [0125] 40 g/l of
lactic acid (synthetic) [0126] 5 g/l of succinic acid [0127] 8 g/l
of malic acid [0128] 1 g/l of citric acid [0129] 10 g/l of sodium
acetate [0130] 5 g/l of ammonium sulphate [0131] 75 ppm of Sn as
tin(II) sulphate [0132] 725 mg/l of Fluowet.RTM. CA from Clariant
[0133] 7 gl of PTFE dispersion Zonyl.RTM. 3807 from DuPont [0134]
15 mg/l of non-ionic surfactant "FSN=100" from DuPont
[0135] The layer thickness achieved is 5 .mu.m.
TABLE-US-00001 TABLE I Useful life PTFE Electrolyte (in MTO)
distribution behaviour Comparative example 1 1 20 vol.-% Not stable
Example 2 3 25 vol.-% Stable Example 3 2 25 vol.-% Stable Example 4
2 25 vol.-% Hardly stable
[0136] The electrolyte behaviour "not stable" means essentially the
formation of a foreign seed in the electrolyte during the layer
formation process.
[0137] The electrolyte behaviour "hardly stable" means the
formation of a foreign seed in the electrolyte after one hour
during the layer formation process.
[0138] The electrolyte behaviour "stable" means no foreign seed
formation in the electrolyte during the layer formation
process.
[0139] Table I clearly shows improved properties of the nickel
alloy dispersion layers according to the invention in comparison
with those of the state of the art.
* * * * *