Note: Descriptions are shown in the official language in which they were submitted.
los6679
This invention relates to electroplating and in
particular to a novel process and a composition having improved
tolerance to higher concentrations of brighteners therein.
To conserve nickel and reduce costs, a number of
procedures have been adopted by the nickel plating industry.
Some of these procedures include reducing the thickness of
nickel deposited, substituting cobalt for some or all of the
nickel when cobalt is less expensive or more readily available,
and more recently electrodepositing nickel-iron, cobalt-
iron, or nickel-cobalt-iron alloys in which as much as 60%
of the deposit may consist of relatively inexpensive iron.
However, when deposit thickness is reduced, it is necessary
to use more effective or "powerful" nickel brighteners or ;
higher concentrations of nickel brighteners, so that the
degree of brightening and leveling to which the nickel -
plating industry has grown accustomed may be obtained. The
more "powerful" nickel brighteners or high concentrations of
brighteners, while capable of producing the desired brightening
and leveling, may nevertheless cause unacceptable side
effects. The nickel deposits may peel or may be highly
stressed, severely embrittled, less receptive to subsequent
chromium deposits or exhibit hazes, reduced low current
density covering power or "throw" or striations and skip
plate, i.e., areas in which a deposit is not obtained.
Although in many respects, the electrodeposition
of nickel-iron, cobalt-iron or nickel-cobalt-iron alloys is
very similar to the electrodeposition of nickel in that
similar equipment and operating conditions are employed;
. .: ,~ - .-
... ...
, " ," ~
1~86679
nevertheless, electroplating with iron containing alloys of
Inickel and/or cobalt presents some special problems. For
,example, one requirement in the electrodeposition of iron
l alloys of nickel and/or cobalt is that the iron in the
I electroplating solution should be predominantly in the
ferrous state rather than the ferric. At a pH of about 3.5,
basic ferric salts precipitate and can clog the anode bags
and filters and may produce rough electrodeposits. It is,
therefore, advantageous to prevent any ferric basic salts
from precipitating. This can be accomplished by the addition
of suitable complexing, chelating, anti-oxidant or reducing
agents to the iron containing electroplating alloy bath as
taught by Koretzky in U. S. Patent 3,354,059; Passa~ in
U. S. Patent 3,804,726; or Clauss et al in U. S. Patent
3,806,429. While these complexing or chelating agen s are
necessary in order to provide a solution to the ferric iron
problem, their use may also result in several undesirable
side effects. They can cause a reduction in deposit leveling
and can also produce striated, hazy or dull deposits which
i
mzy further exhibit step plate or even skip plate, i.e.,
areas which are not plated, or else plated only very thinly
~ compared to other sections of the deposits.
¦l In order to overcome the deleterious effects of
1 high concentrations of brighteners or "powerful" brighteners,
1 or to countelract the undesirable side effects of iron or
iron solubilizing substances when these are present in nickel
!l - .-.
.
~0~6679
and/or cobalt, or iron containing nickel and/or cobalt
electroplating baths, the addition of various sulfinic acids
or their salts has been recommended by Brown in ~. S. Patent
2,~54,703. Unfortunately, the sulfinic acids and their
salts are unstable and subject to rapid oxidation by the
oxygen of the atmosphere to the corresponding sulfonic acids
or sulfonate salts, in which state they are no longer
efficatious in overcoming the various side effects mentioned
above. The use of sulfinic acids or their salts also severely
reduces deposit leveling,
This invention attempts to provide processes and
compositions for depositing electrodeposits of nickel, cobalt,
or binary or ternary alloys of the metals selected from
nickel, cobalt and iron which possess a greater tolerance
for hîgh concentrations of brighteners and furthermore to
provide deposits of nickel, cobalt or binary or ternary
alloys of the metals selected from nickel, cobalt and iron
characterized by increased ductility, brightness, covering
power, and leveling or scratch hiding ability. It is believed
that the compositions of this invention overcome the problems
caused by the presence of iron or iron solubilizing materials
in iron alloy electroplating baths of nickel and/or cobalt.
-- 3 --
~01~6679
In accordance with certain of its aspects, this
invention relates to a process and a composition for the prepar-
ation of an electrodeposit which contains; at least one metal
selected from the group consisting of nickel and cobalt or; binary
or ternary alloys of the metals selected from nickel, iron, and
cobalt; which comprises passing current from an anode to a
cathode through an aqueous acidic electroplating solution
containing at least one member selected from nickel compounds
and cobalt compounds and which may additionally contain iron
compounds providing nickel, cobalt and iron ions for electro-
depositing nickel, cobalt, nickel-cobalt alloys, nickel-iron
alloys, cobalt-iron alloys or nickel-iron-cobalt alloys;
the improvement comprising the presence of 5 x 10 6 moles per
liter to 0.5 mole per liter of an unsaturated cyclosulfone
exhibiting the following generalized structural formula:
~ R3
~S,~o
O
wherein Rl, R2, R3 and R4 are independently hydrogen, lower alkyl,
or hydroxyl; for a time period sufficient to form a metal electro-
plate upon said cathode.
- 4 -
10~66 7g ~
The baths of this invention may also contain an
effective amount of at least one member selected from the
group consisting of:
l (a) Class I brighteners
I (b) Class II brighteners
(c) Anti-pitting or wetting agents
The term "Class I brighteners" as used herein, and
as described in Modern Electroplating, Thir~ Edition,
F. Lowenheim, Editor, is meant to include aromatic sulfonates,
sulfonamides, sulfonimides, etc., as well as aliphatic or
aromatic-aliphatic olefinically or acetylenically unsaturated
sulfonates, sulfonamides, sulfonimides, etc. Specific examples
of such plating additives are:
~ (1) sodium o-sulfobenzimide
~l (2) disodium 1,5-naphthalene disulfonate
(3) trisodium 1,3,6-naphthalene trisulfonate
(4) sodium benzene monosulfonate
! (5) dibenzene sulfonimide
j' (6) sodium allyl sulfonate
~i` (7) sodium 3-chloro-2-butene-1-sulfonate
i' (8) sodium ~-styrene sulfonate
~! (9) sodium propargyl sulfonate
'~ (10) monoallyl sulfamide
Il (11) diallyl sulfamide
li (12) allyl sulfonamide
.
_5_
108~i67-
Such plating additive compounds, which may be used
singly or in suitable combinations, are desirably employed
in amounts ranging from about 0.5 to 10 grams per liter and
~ provide the advantages described in the above reference and
which are well known to those skilled in the art of nickel
electroplating.
The term "Class II brighteners" as used herein,
and as described in Modern Electroplating, ~hird Edition,
F. Lowenheim, Editor, is meant to include plating additive
compounds such as reaction products of epoxides with alpha-
hydroxy acetylenic alcohols such as diethoxylated 2-butyne-
1, 4-diol or dipropoxylated 2 butyne-1,4-diol, other acetylenics,
N-heterocyclics, dye-stuffs, etc.
Specific examples of such plating additives are:
~1) 1,4-di-(~-hydroxyethoxy)-2-butyne
(2) 1,4-di-(~-hydroxy-y-chloropropoxy)-2-butyne
(3) 1,4-di-(~ -epoxypropoxy)-2-butyne
(4) 1,4-di-(~-hydroxy-~-butenoxy)-2-butyne
~ (5) 1,4-di-(2'-hydroxy-4'-oxa-6'-heptenoxy)-2-butyne
, (6) N-(2,3-dichloro-2-propenyl)-pyridinium chloride
(7) 2,4,6-trimethyl N-propargyl pyridiniu~.. bromide
(8) N-allylquinaldinium bromide
! ~ ( 9, 2-butyne-1,4-diol
ll (10) propargyl alcohol
li (11) 2-methyl-3-butyn-2-ol
jl (12) quinaldyl-N-propanesulfonic acid betaine
I .
I - 6 - I
.. ~. ..... . ~ . ~ . ... .
1013~;679
(13) quinaldine dimethyl sulfate
(14) N-allylpyridinium bromide
(15) isoquinaldyl-N-propanesulfonic acid betaine
l (16) isoquinaldine dimethyl sulfate
(17) N-allylisoquinaldine bromide
¦ (18) 1,4-di~ sulfoethoxy)-2-butyne
(19) 3-(~-hydroxyethoxy)-propyne
~, (20) 3-(~-hydroxypropoxy)-propyne
~ (21) 3-(~-sulfoethoxy)-propyne
.l (22) phenosafranin
,i (23) fuchsin
When used alone or in combination, desirably in
amounts ranging from about 5 to 1000 milligrams per liter, a
Class II brightener may produce no visual effect on the
electrodeposit, or may produce semi-lustrous, fine-grained
deposits. However, best results are obtained when Class II
brighteners are used with one or more Class I brighteners in
order to provide optimum deposit luster, rate of brightening,
leveling, bright plate current density range, low current
density coverage, etc.
The term "anti pitting or wetting agents" as used
herein is meant to include a material which functions to
prevent or minimize gas pitting. An anti-pitting agent,
when used alone or in combination, desirably in amounts
r~nging from about 0.05 to 1 gram per liter, may also
function to make the baths more compatible with contaminants
10~6~
such as oil, grease, etc. by their emulsifying, dispersing,
` solubilizing, etc. action on such contaminants and thereby
j promote attaining of sounder deposits. Preferred anti-pitting
agents ma~ include sodium lauryl sulfate, sodium lauryl ether-
sulfate and sodium di-alkylsulfosuccinates.
- The nickel compounds, cobalt compounds and iron
compounds employed to provide nickel, cobalt and iron ions
for electrodeposit ng nickel, cobalt, or binary or ternary
alloys of nickel, cobalt and iron, (such as nickel-cobalt,
nickel-iron, cobalt-iron and nickel-cobalt-iron alloys) are
typically added as the sulfate, chloride, sulfamate or
fluoborate salts. The sulfate, chloride, sulfamate or
fluoborate salts of nickel or cobalt are employed in concen-
trations sulficient to provide nickel and/or cobalt ions in
the electroplating solutions of this invention in concen-
trations ranging from about 10 to 150 grams per liter. The
iron compounds, such as the sulfate, chloride, etc. when
added to the nickel, cobalt, or nickel and cobalt containing
electroplating solutions of this invention, are employed in
concentrations sufficient to provide iron ions ranging in
concentration from about 0.25 to 25 grams per liter. The
ratio of nickel ions or cobalt ions or nickel and cobalt
ions to iron ions may range from about 50 to 1 to about
5 to 1.
~I .
- 8 -
1~t36679
The iron ions in the electroplating solutions of this
invention may also be introduced through the use of iron anodes,
rather than through the addition of iron compounds. Thus, for
example, if some percentage of the total anode area in a nickel
electroplating bath is composed of iron anodes, after some period
of electrolysis enough iron will have been introduced into the bath
by chemical or electrochemical dissolution of the iron anodes to
provide the desired concentration of iron ions.
The nickel, cobalt, nickel-cobalt, nickel-iron, cobalt-
iron and nickel-cobalt-iron electroplating baths of this invention
additionally may contain from about 30 to 60 grams per liter, pre-
ferably about 45 grams per liter of boric acid or other buffering
agents to control the pH (e.g. from about 2.5 to 5, preferably
about 3 to 4) and to prevent high current density burning.
When iron ions are present in the plating baths of
this invention, the inclusion of one or more iron complexing,
chelating, anti-oxidizing, reducing, or other iron solubilizing
agents such as citric, malic, glutaric, gluconic, ascorbic,
isoascorbic, muconic, glutamic, glycollic, and aspartic acids
or similar acids or their salts are desirable in the iron con-
taining baths to solubilize iron ions. These iron complexing or
solubilizing agents may range in concentration in the plating
solution from about one gram per liter to about 100 grams per
liter, depending on how much iron is present in the plating bath.
.. : ;. ' ~
Il , j
1~6679
In order to prevent "burning" of high current
density areas, provide for more even temperature control of
the solution, and control the amount of iron in the iron
containing alloy deposits, solution agitation may be employed.
Air agitation, mechanical stirring, pumping, cathode rod and
other means of solution agitation are all satisfactory.
Additionally, the baths may be operated without agitation.
The operating temperature of the electroplating
baths of this invention may range from about 40C to about
85C, preferably from about 50C to 70.
The average cathode current density may range from
about 0.5 to 12 amperes per square decimeter, with 3 to 6
amperes per square decimeter providing an optimum range.
, Typical aqueous nickel-containing electroplating
baths (which may be used in combination with effective
amounts of cooperating additives) include the following
wherein all concentrations are in grams per liter (g/l)
unless otherwise indicated:
,, I
Il TABLE I
AQUEOUS NICKEL-CONTAINING ELECTROPLATING BATHS
~I Minimum Maximum Preferred
.' !
Component:
SO4 2
' 2 6 2 20 100 60
ll H3BO3 30 60 45
Il pH (electrometric) 3 5 4
- 10 - ~
~! 1
~! I
Il 1086679
When ferrous sulfate (FeSO4~7H2O) is included in
the foregoing bath the concentration is about 2.5 grams per
¦~liter to about 125 grams per liter.
I! Typical sulfamate-type nickel plating baths which
may be used in the practice of this invention may inc~ude
the following components:
¦¦ TABLE II
~i AQUEOUS NICKEL SULFA~TE ELECTROPLATING BATHS
,~ Minimum rlaximum Preferred
Component:
Nickel Sulfamate 100 500 375
iC 2 2 10 100 60
H3BO3 30 60 45
pH (Electrometric) 3 5 4
When ferrous sulfate (FeSO4-7H2O) is included in
the foregoing bath the concentration is about 2.5 grams per
liter to about 125 grams per liter.
Typical chloride-free sulfate-type nickel plating
baths which may be used in the practice of this invention may
include the following components:
TABLE III
AQUEOUS CHLORIDE-FREE NICKEL ELECTROPLATING BATHS
Minimum Maximum Preferred
Component:
4 2 100 500 300
'' H3BO3 30 60 45
.! pH (Electrometric) 2.5 4 3-3.5
When ferrous sulfate (FeSO4-7H2O) is included in
the foregoing baths the concentration is about 2.5 grams per
liter to about 125 grams per liter
1~86679
Typical chloride-free sulfamate-type nickel plating
baths which may be used in the practice of this invention may
:linclude the following components:
~¦ TABLE IV
AQUEOUS CHLORIDE-FREE NICKEL SULFAMATE ELECTROPLATING BATHS
¦¦ MinimumMaximum Preferred
Component:
Nickel sulfamate 200 500 350
Il H3BO3 30 60 45
pH (Electrometric) 2.5 4 3-3.S
When ferrous sulfate (FeSO4 7H2O) is included in the
foregoing baths the concentration is about 2.5 grams per liter
to about 125 grams per liter.
The following are aqueous cobalt-containing and
cobalt-nickel-containing electroplating baths which may be used
in the practice of this invention:
TABLE V
. AQUEOUS COBALT-CONTAINING AND COBALT-NICKEL-
, CONTAINING ELECTROPLATING BATHS
1 (All concentrations in g/l unless otherwise noted)
~'. Minimum Maximum Preferred
Cobalt bath
, CoS4 7H2 50 500 300
CC12 6H2 15 125 60
1. H3BO3 30 60 45
Cobalt bath
' CoSO4 7H2O 100 500 400
', NaCl 15 60 30
Il H3BO3 30 60 45
" . . . I
- : ,
10t~6679
TABLE V (cont.)
Minimum Maximum Preferred
High chloride cobalt bath
¦ CoSO4 7H2O 75 350 225
i C0C12 6H2 50 350 225
ll H3BO3 30 60 45
Cobalt-nickel alloy bath
ii NiS04 6H2O 75 400 300
il CoSO4 7 2 15 300 80
j 2 2 15 75 60
~i H3BO3 30 60 45
All-chloride cobalt bath
CoCl 6H O 100 500 300
H3BO3 30 60 45
Sulfamate cobalt bath
Cobalt sulfamate 100 400 290
~5 I' CoCl 6H O 15 76 60
1 H3BO3 30 60 45
¦l The pH in the typical formulations of Table V may
range from about 3 to 5 with 4 preferred.
i When ferrous sulfate (FeSO4 7H2O) is includ~d in
the foregoing baths the concentration is about 2.5 grams per
:~ liter to 125 grams per liter.
Typical nickel-iron containing electroplating
baths which may be used in the practice of this invention
may include the following components:
Il ,
~1 - 13 -
- : ,
: .
86679
TABLE VI
AQUEOUS NICKEL-IRON ELECTROPLATING BATHS
Minimum Maximum Preferred
Component:
NiS04 6 2 20 500 200
i! NiC12 6H20 15 300 60
~ FeS4 7H2 1 125 40
H3BO3 60 45
pH tElectrometric) 2.5 5 3.5-4
I'
j With the inclusion of ferrous sulfate (FeSO4-7H2O)
in the foregoing bath formulations it is desirable to
additionally include one or more iron complexing, chelating
or solubilizing agents ranging in concentration from about 1
gram per liter to about 100 grams per liter, depending on
the actual iron concentration.~
It will be apparent that the above baths ~ay
contain compounds in amounts falling outside the preferred
minimum and maximum set forth, but most satisfactory and
economical operation may normally be effected when the
compounds are present in the baths in the amounts indicated.
The pH of all of the foregoing illustrative
aqueous nickel-containing, cobalt-containing, nickel-cobalt-
containing, nickel-iron, cobalt-iron and nickel-cobalt-iron-
containing compositions may be maintained during plating at
pH values of 2.5 to 5.0, and preferably from about 3.0 to
4Ø During bath operation, the pH may normally tend to
rise and may be adjusted with acids such as hydrochloric
acid, sulfuric acid, etc.
I - 14 -
..
1086679
Anodes used in the above ~aths may consist of ehe
particular single metal being plated at the cathode such as
` nic];el cr cobalt for plating nickel or cobalt respectively.
~` For plating binary or ternary alloys such as nickel-cobalt,
~ cobalt-iron, nickel-iron or nickel-cobalt-iron, the anodes
may consist of the separate metals involved suitably suspended
in the bath as bars, strips or small chunks in titanium
baskets. In such cases the ratio of the separate metal
anode areas is adjusted to correspond to the particular
cathode alloy composition desired. For plating binary or
ternary alloys one may also use as anodes alloys of the
metals involved in such a percent weight ratio of the separate
metals as to correspond to the percent weight of the same
metals in the cathode alloy deposits desired. These two
types of anode systems will generally result in a fairly
constant bath metal ion concentration for the respective
metals. If with fixed metal ratio alloy anodes there does
occur some bath ion imbalance, occasional adjustments may be
made by adding the appropriate corrective concentration of
the ~ndividual metal salts. All anodes are usually suitably
covered with cloth or plastic bags of desired porosity to
minimize introduction into the bath of metal particles,
anode slime, etc. which may migrate to the cathode either
mechanically or electrophoretically to give roughness in
cathode deposits.
The substrates on which the nickel-containing,
cobalt-containing, nickel-cobalt-containing, nickel-iron-
containing, cobalt-iron-containing or nickel-cobalt-iron-
containing electrodeposits of this invention may be applied
li
~ - 15 -
~OB6679
may be metal or metal alloys such as are commonly electro-
deposited and used in the art of electroplating such as
nickel, cobalt, nickel-cobalt, copper, tin, brass, etc.
j Other typical substrate basis metals from which articles to
be plated are manufactured may include ferrous metals such
as iron, steel, alloy steels, copper, tin and alloys thereof
such as with lead, alloys of copper such as brass, bronze,
etc., zinc, particularly in the form of zinc-base die castings;
, i
all of which may bear plates of other metals, such as copper,
10 ` etc. Basis metal substrates may have a variety of surface
finishes depending on the final appearance desired, which in
turn depends on such factors as luster, brilliance, leveling,
thickness, etc. of the cobalt, nickel, or iron containing
electroplate applied on such substrates.
i While nickel, cobalt, nickel-cobalt, nickel-iron,
cobalt-iron or nickel-iron-cobalt electrodeposits can be
obtained employing the various parameters described above,
the brightness, leveling, ductility and covering power may
not be sufficient or satisfactory for a particular appli-
cation. In addition, the deposits may be hazy or dull, and
also exnibit striations, step plate, peeling or poor chromium
receptivity. These conditions may especially result after
the addition of excessive replenishment amounts of Class II
brighteners, or from the use of especially "powerful" Class
II brighteners. In the case of the iron-containing plating
- 16 -
lOB66'79
l baths which additionally contain iron solubilizing agents,
;:the iron or the iron solubili~ing agents may also cause a
loss of leveling and brightness, or may result in hazy, dull
or striated deposits. I have discovered that the addition or
inclusion of certain bath compatible unsaturated cyclosulfones
when added to an aqueous acidic nickel, cobalt, nickel-
cobalt, nickel-iron, cobalt-iron or nickel-iron-cobalt
electroplating bath will correct the aforementioned deficiencies.
Additionally, the unsaturated cyclosulfone compounds of this
invention permit the use of higher than normal concentrations
of Class II brighteners, thus permitting higher rates of
brightening and leveling without the undesirable striations,;
skip plate, brittleness, etc. normally expected under these
conditions.
These bath soluble unsaturated cyclosulfones are
characterized by the following structural formula:
Rl ~R4
C~
wherein
~I R,, R2, R3 and R4 are independently hydrogen, lower
~ alkyl, or hydroxyl.
- 17 -
,. : ' ; ~ . . .
1~6679
IIt is understood that bath compatible substituent groups such
las chloride, bromide, alkoxy, etc., which in themselves do not
contribute to the efficacy of the unsaturated cyclosulfone5i~
but are either inert w1 h respect to the electroplating solution,
lior may provide increased bath solubility to the parent sulfone,
may also be present.
~¦ Typical or representative compounds which are
characterized by the above generalized formula are listed
but not limited to the following:
2,5-Dihyd ro thiophene-l,l-dioxide
(Sulfolene) O~S~O
3-M~thylsulfolene Q
H3 ~
2 4-Dimethylsulfolene Q CH
,2-Hydroxysulfolene Q -Od
- 18 -
. .
1086679
The unsaturated cyclosulfones of this invention are
unusual in that they do not act as brighteners per se in the
same way as brighteners of the first or second class and
therefore should not be thought of as brighteners, but rather
~' as addition agents whose function in the bath is to overcome
haze, striation, peeling, step and skip plate. In addition,
the low current density coverage and deposit leveling may
~ ! ,
be improved by the addition of these compounds to nickel,
cobalt, nickel-cobalt, nickel-iron, cobalt-iron or nickel-
cobalt-iron electroplating baths.
The unsaturated cyclosulfones of this invention are
employed in the electroplating baths of this invention at
concentrations of from about 5 x 10 6 moles per liter to about
0.5 mole per liter and preferably from about 1 x 10 5 moles
per liter to 0.1 mole per liter.
The following examples are presented as an illustration
to provide those skilled in the art of electroplating a better
understanding of the various embodiments and aspects of this
invention. These examples should not be construed as limiting
the scope of the invention in any way.
i
: :
1~6679
Example 1
An aqueous nickel electroplating bath was prepared
having the following composition:
Composition in g/l
NiS4-6H2 300
iC12 6 2 60
H3B03 45
Sodium o-sulfobenzimide 3.6
Sodium allyl sulfonate 3.7
1,4-di~-hydroxyethoxy)-2-butyne 0.2
pH 3.8
Temperature 57C -
A polished brass panel was scribed with a horizontal
single pass of 4/0 grit emery polishing paper to give a band
about 1 cm wide at a distance of about 2.5 cm from-and parallel
to the bottom edge of the panel. The cleaned panel was then
plated in a 267 ml Hull Cell, using the above solution, for
10 minutes at 2 amperes cell current, using magnetic stirring.
The resulting nickel deposit was brilliant but exhibited severe
striations across the entire current density range of the test
panel. Additionally, the deposit was thin and dark in the
region from about zero to 1.2 amperes per square decimeter ~ASD)
and peeled in the region from about 1.5 ASD to the high current
density edge of the test panel (about 12 ASD). The poor physical
characteristics of the deposit (i.e., striations, dark areas,
peeling) were due to the relatively high concentration of
Class II brightener.
-20-
10~-679
On adding 4.1 x 10 3 moles per liter (0.5 gram per
liter) of tetrahydrothiophene-l,l-dioxide, (sulfolane)
CH2-CH2-CH2-SO2-~H2, to the plating solution and repeating
the plating test, the resulting nickel deposit was identical
to that obtained initially. Increasing the sulfolane
concentration to 4.1 x 10 2 moles per liter (5 grams per liter)
in the plating solution and repeating the test, likewise had
no observable effect on the resulting nickel deposit.
~ i
Example 2
An aqueous nickel electroplating bath was prepared
and tested in the manner described in the first part of Example 1.
The resulting nickel deposit suffered the same faults as pre-
viously mentioned.
On adding 3.4 x 10 3 moles per liter (0.4 grams per
liter) of 2,5-dihydrothiophene-1,1-dioxide, (sulfolene)
CH=CH-CH2-SO2-CH2, to the test solution and repeating the
plating test, the resultant nickel deposit was uniformly
brilliani across the-entire current density range and was
free of the striations, low current density darkness and
peeling observed initially.
- 21 -
1~86679
~ Example 3
li
¦l An aqueous nickel electroplating bath was prepared
,and tested in the manner described in the first part of Example 1
~Iwith the deposit exhibiting striations, peeling and low current
~density darkness as already noted.
On adding 7.6 x 10 3 moles per liter (1.0 gram per
- liter) of 3-methyl-2,5-dihydrothiophene-1,1-dioxide, (3-methyl-
sulfolene) CH=CH-CH(CH3)-SO2-CH2, to the test solution and
repeating the plating test, the resultant nickel deposit was
brilliant across the entire current density range of the test
panel, exhibited excellent leveling as indicated by the oblit-
eration or filling in of the emery scratches and was free of
striations and deposit peeling.
Example 4
il An aqueous nickel electroplating bath was prepared and
tested in the manner described in the first part of Example 1.
The resulting nickel deposit suffered the same faults as mentionedl
previously. I -
~1 On adding 6.8 x 10 3 moles per liter (1.0 gram per
20 ~1 liter) of 2,4-dimethyl-2,5-dihydrothiophene-1,1-dioxide,
! (2,4-dimethyl-3-sulfolene) CH=C(CH3)-CH2-SO2-CH(CH3), to the test
~ solution and repeating the plating test, the resultant nickel
!I deposit was brilliant over the entire current density range and
Il the striations, deposit peeling and low current density darkness
25 1! were significantly reduced or eliminated.
: .:
1086679
Example 5
An aqueous nickel-iron electroplating bath was prepared
having the following composition:
~ Composition in g/l
1 NiSO 6~i 0 150
l . NiC12- 6H20 go
¦¦ FeS04 7H20 40
ij 3 3 49
, Iso-ascorbic acid 2
IZ Sodium o-sulfobenzimide 3.6
i¦ Sodium ailyl sulfonate 3.5
l 1,4-di(~-hydroxyethozy)-2-butyne 0.1
Il 3.2 Z
¦ Temperature 55C
, ~ !
I,l A polished brass panel was scribed with a horizontal
single pass of 4/0 grit emery polishing paper to give a band l ;
about 1 cm wide at a distance of about 2.5 cm from and parallel
to the bottom edge of the panel. The cleaned panel was then
plated in a 267 ml Hull Cell, using the above solution, for
10 minutes at 2 amperes cell current, using magnetic stirring.
The resulting nickel-iron deposit was bright and well leveled
from about ~.5 ASD to the high current density edge of the test
panel. However, in the current density range from about zero
i to 2.5 ASD, the deposit was dark and non-uniform and exhibited
step plate.
On adding 3.4 x 10 3 moles per liter (0.4 gram per
, liter) of 2,5-dihydrothiophene-1,1-dioxide (sulfolene) to the
plating solution and repeating the plating test, the resulting
66~
linickel-iron deposit was free of the low current density darkness
,land step plate noted above and exhibited a uniform transition
,between middle and low current density areas.
Although this invention has been illustrated by
reference to specific embodiments, modifications thereof which
are clearly within the scope of the invention will be apparent
to those skilled in the art.
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