ELECTRODEPOSITION OF ZINC

ZINGAGE PAR ELECTRODEPOSITION

English Abstract

U 10,715/BFC:au
ELECTRODEPOSITION OF ZINC
ABSTRACT OF THE DISCLOSURE
The instant invention is directed to an aqueous alkaline
zinc-electroplating bath and to a process of utilizing the same,
the bath comprising a source of zinc ions, and an effective zinc
brightening amount of a bath soluble multiple quaternary compound
which is the reaction product of a polyalkylene amine having a
molecular weight of from about 60 to 1000, and an organic quater-
nary ammonium halide which contains a halogen which will react
with at least one-fourth of the available amino groups in the
polyalkylene amine.

Claims

J 10,715
The embodiments of the invention in which an exclusive
property or privilege is claimed are defined as follows:
1) An aqueous alkaline zinc electroplating bath, comprising
a source of zinc ions 9 and an effective zinc brightening amount
of a bath soluble multiple quaternary compound which is the reaction
product of a polyalkylene amine having a molecular weight of from
about 60 to 1000, and an organic quaternary ammonium halide which
contains a halogen which will react with at least one-fourth of
the available amino groups in the polyalkylene amine.
2) A zinc electroplating bath as defined in Claim 1, in
which the source of zinc ions is zinc metal present in the amount
of about 2 to 50 grams per liter, and in which the reaction product
is present in the bath in an amount ranging from about 5 milligrams
to 10 grams per liter.
3) A zinc electroplating bath as defined in Claim 1, in
which the source of zinc ions is zinc metal present in the amount
of approxiamtely 6 to 30 grams per liter, and in which the reaction
product is present in the bath in an amount of from about 10
milligrams to 4 grams per liter.
4) A zinc electroplating bath as defined in Claim 1, in
which the polyalkylene amine has the formula:
<IMG>
wherein:
R1 = H, alkyl of 1-4 carbon atoms;
R2 = -OH, H, -COOH, alkyl of 1-4 carbon atoms;
R3 = H, alkyl, hydroxyalkyl, carboxyalkyl, alkoxy of
1-4 carbon atoms;
m = 0-4; and
n = 1-24. 12

5) A zinc electroplating bath as defined in Claim 1, in
which the organic quaternary ammonium halide has the formula:
<IMG>
wherein R may be <IMG> is hydrogen or
alkyl of 1 to 4 carbon atoms, and X is a halogen.
6) A zinc electroplating bath as defined in Claim 1, in
which the polyalkylene amine has the formula:
<IMG>
wherein:
R1 = H, alkyl of 1-4 carbon atoms;
R2 = -OH, H, -COOH, alkyl of 1-4 carbon atoms;
R3 = H, alkyl, hydroxyalkyl, carboxyalkyl, alkoxy of
1-4 carbon atoms;
m = 0-4; and
n = 1-24
and the organic quaternary ammonium halide has the formula:
<IMG>
wherein R may be <IMG> is hydrogen or
alkyl of 1 to 4 carbon atoms and X is a halogen.
7) A zinc electroplating bath as defined in Claim 6, in
which the source of zinc ions is zinc metal present in the amount
13

U-10,715
of about 2 to 50 grams per liter, and in which the reaction
product is present in the bath in an amount ranging from about
5 milligrams to 10 grams per liter.
8) A zinc electroplating bath as defined in Claim 6,
in which the source of zinc ions is zinc metal present in the
amount of approximately 6 to 30 grams per liter, and in which
the reaction product is present in the bath in an amount of
from about 10 milligrams to 4 grams per liter.
9) A zinc electroplating bath as defined in Claim 1,
in which the polyalkylene amine has the formula:
<IMG>
wherein:
R1 = H, alkyl of 1-4 carbon atoms;
R2 = -OH, H, -COOH, alkyl of 1-4 carbon atoms;
R3 = H, alkyl, hydroxyalkyl, carboxyalkyl, alkoxy of
1-4 carbon atoms;
m = 0-4; and
n = 1-24
and the organic quaternary ammonium halide has the formula:
<IMG>

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10) A zinc electroplating bath as defined in Claim 9,
in which the reaction product has the formula:
<IMG>
wherein R3 is as defined above.
11) A zinc electroplating bath as defined in Claim 9, in
which the source of zinc ions is zinc metal present in the amount
of about 2 to 50 grams per liter, and in which the reaction product
is present in the bath in an amount ranging from about 5 milligrams
to 10 grams per liter.
12) A zinc electroplating bath as defined in Claim 9, in
which the source of zinc ions is zinc metal present in the amount
of approximately 6 to 30 grams per liter, and in which the reaction
product is present in the bath in an amount of from about 10
milligrams to 4 grams per liter.
13) A method of depositing zinc from an aqueous alkaline
zinc electroplating bath, which comprises passing an electric
current from an anode through the bath of Claim 1 to a catholic
workpiece for a period of time sufficient to form a zinc deposit.
14) A method of depositing zinc from an aqueous alkaline
zinc electroplating bath, which comprises passing an electric
current from an anode through the bath of Claim 9 to a cathodic
workpiece for a period of time sufficient to form a zinc deposit,
the temperature of said bath being between about 15°C. to 45°C.,

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the cathode current density varying from about 5 to 100 amps. per
sq.ft., and the anode current density being from about 5 to 35
amps. per sq. ft.
16

Description

U 10,71S
B~CK~ROUND OF TH~ INV~NTION
It is known in the art to which this invention pertains to
provide an electroplating bath useful for the electrodeposition of
zinc, comprising an alkaline electrolyte preferably containing aIkal;
rnetal zincate and also containing a reaction product of a poly-
alkylene imine having a molecular ~eight from about 300 to 1,000,000
and an organic quaternary ammonium halide which contains a halogen
which will quaternize a nitrogen of the polyalkylene imine in a ratio
of one mole of organic ammonium halide to two mole-units of the poly-
alkylene imine. A composition of this character is specifically
disclosed in U.S. Patent No. 3,853,718 dated December 10, 1974,
and which is assigned to the assignee of the instant application.
While the inventive concept described in the mentioned
patent has fulfilled a need long existing in the art, the instant
applicants have discovered that substantially improved results by
way of plating solution stability as well as ductility and bright-
ness of the zinc deposits are achieved by utilization in the bath
of a small chain reaction product of a polyalkylene amine having
a molecular ~eight in the range of 60 to 1000, and an organic
ammonium halide containing a halide capable of quaternizing or
alkylating a nitrogen of the polyalkylene amine so as to produce
a plurality o~ nitrogcn qu~ternary sites.
In general, the reaction procceds as ~ollows:
C~l ~C1 1 2~n N1 31n
wllercin;
Rl = H, alkyl of 1-4 carbon atoms;
R2 = -OH, H, -COOH, alkyl of 1-4 carbo~ Atoms;
2~

U 109715
.
R3 = H, alkyl, hydroxyalkyl, carboxyalkyl, alkoxy of
1-4 carbon atoms;
m = 0-4; and
n = 1-24
.~
X--R--N~3 (Rq) ~
X0
wherein:
X = halogen
R4 a H, alkyl of 1-4 carbon atoms,
or more specifically, I
~~ ~7 ' '
R~N~9 (R4) 3
I x~ : .
~ ~ _ ~-N~ ~----.- .~ .. _
Ix~ . ~
, R
wherein: 0~
R = CH2 - CH - CH2
R3, R4 and X are defined as above.
The resulting reaction product contains structural units as
previously described.
DESCRIPTION QF THE PRE~ERRED EMBODIMEN'I`
Appl.icants' invention is directed to the electrodeposition
of zinc accomplished by utilization of an electroplating bath
incorporating therein a source of zinc ions perferably provided by
zinc metal in the amount of about 2 to 50 grams per liter, and more

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specifically approximately 6 to 30 grams per liter, and a bath
soluble multiple quaternary compound which is the reaction product,
firstly, of a polyalkylene amine having a molecular weight of from
about 60 to 1000, and secondly, an organic quaternary ammonium
halide which contains a halogen capable o reacting with at least
one-fourth of the available amino groups in the polyalkylene amine.
In accordance with this invention, the reaction product as thus
formed in the bath is present in an amount ranging from about 5
milligrams to 10 grams per liter, and more specifically, 10 milli-
grams to 4 grams per liter.
The present invention is of application to a wide variety
of zinc electroplating bat~,including those ~hich are known in
the art as zincate or essentially cyanide-free baths, and those
commonly referred to as high to low cyanide-containing baths~ In
zincate plating baths there is generally present an admixture of
zinc oxide and caustic. The amount of al~ali metal hydroxide may
range from about 50 to 200 grams per liter a and the source of zinc
ions is as earlier indicated.
The processing parameters are such that normally atmospheric
temperature and pressure are employed, although temperatures of up
to 55C. may be used, and even more preferably about 15 to 45C.
The cathode current density may vary Erc~ about 5 to 100 amps.
p~r sq.t., w}lile the anode current density rallges from approximate-
ly 5 to 35 amps. per Sq.~t.
The zinc brightening a~ent that may be elllployed in the
present invention is one that employs as a reactant polyalkylelle
amine. It is to be appreciated that the reaction product that is
to be used as a zinc brightener in the instant invention is one
that should be soluble in the aqueous alkaline system. The poly-
alkylene amine that is utilized is a lo~er alkyl substitute of
.

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polyethylene amine, that is a polyethylene amine in which one or
more of the hydrogens are substituted by a lower alkyl, such as a
one to three carbon alkyl radical, such as methyl, ethyl, and
n-propyl or isopropyl and including the substitution derivatives
in which one or more alkyl hydrogens are replaced by a bath compati-
ble organic radical, such as for example, carboxyl, esterified
carboxyl, aldehyde, acetyl, ether carbonyl, and other bath
compatible radicals, such as the hydroxy or amino radicals. It is
particularly preferred that the polyalkylene amine be unsubstituted
polyethylene amineswhich are generally available to the public.
The polyethylene amine can be expressed as the polymeriza-
tion product of the compound of Formula I;
Il l2
HN -~CH - CH -~CH23~m ~ ~~n H
R3 R3
wherein:
Rl = H, alkyl of 1-4 carbon atoms;
R2 = -OH, H, -COOH, alkyl of 1-4 carbon atoms;
R3 = H, alkyl, hydroxyalkyl, carboxyalkyl, alkoxy of
1-4 carbon atoms;
m = 0-4; and
n = 1-24.
The polyalkylene aminc, preEerably ullsubstitlltcd polyethylene
amine, may range from about 60 to 1000 in molecular ~eig}lt, and
here;n lies an important patentable distinction over the disclosurc
in commonly assigned U.S. Patent No. 3,853,718 to which rCel`ellCe
was carlier made. As was mentioned previollsly, by proceeding in
accordance ~ith the instant inve~ion, markedly improved results
by ~ay of plating solution stability, as ~ell as ductility and
brightness of th~ zinc deposits are achieved by utilization in the
'~'
~ -5-

10,715
bath of a small chain reaction product of a polyalkylene amine
having a molecular weight in the range of 60 to 1000.
The zinc brightening agent that is to be employed in the
present case preferably has a plurality of nitrogen quaternary
ammonium sites. One of the quaternaries is in the repeating
polyalkylene amine unit, while the side chain attached to the
quaternary of the polyalkylene amine would be the second site or
a quaternary nitrogen. The multiple nitrogen quaternary that may
be employed herein is one that may be obtained by reacting the
compound of Formula II;
X -R- N~ (R4)3
X~
with the aforementioned polyalkylene amine, wherein R may be
OH
-CH2 - CH - CH2 ~ R4 may have up to 4 carbon atoms per R4 group,
and X is a halogen.
A more specific formula representative of that defined
immediately above is;
OH
Cl - CH2 - CH -CH2- N (~H3)3
Cl~
When one quaternizes the nitrogen of Formula I polymer-
ization products with the compound of Formula II, there are obtained
ploducts having some structrual units of Formula III;
- 0~3
C~l2 -Cll Cl-l2 N (C~l3)3
I Cl~
- N~
l3 Cl~
As can be appreciated, other agents may be l)rescnt in the
bath in ordcr to impart other desirable characteristics such ~s
improving the throwing powcr o~ the bath to low currcnt density
i,. ~
.

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areas, and improving the bath solubility of the components. Suit-
able agents are anisaldehyde, glue, polyvinyl alcohol and the gly-
cerol esters of polyvinyl alcohols having a molecular weight of
5,000 to 20,000. Other polymers that may be employed are gelatin,
peptone and the like. In addition, chelating atents, or agents that
can form a complex ~Yith the zinc in the bath may also be utilized,
such as nitrilo triacetic acid and the various alkali metal salts,
such as the sodium salt, ethylene diamine tetra acetic acid, and
its water soluble salts, such as sodium and the like.
As has been indicated above, the novel concepts of this
invention are applicable to cyanide-free or zincate baths as well
as to cyanide-contsining zinc baths, and in the examples now to
follow there will be set forth test data on both types of baths.
Generally stated, there is provided in an aqueous alXaline zinc
electroplating bath a source of zinc ions and an effective zinc
brightening amount of a bath soluble multiple quaternary compound
which is the reaction product of a polyalkylene amine having a
molecular weight of from about 60 to 1000, and an organic quaternary
ammonium halide which contains a halogen which will react with
at least one-fourth of the available amino groups in the poly-
alkylene amine. More specifically, the source of zinc ions is
preferably provided by zinc metal in the amount of about 2 to 50
grams per liter, and to be more precise, approximately 6 to 30
~rams per liter, and a reaction product as herein defined wllich is
present in the bath in an amount ranging from about 5 milligrams
to 1~ grams per liter, and more particularly, 10 millig`rams to
4 grams per liter.
The invention will be more fully understood when reference
is made to the following examples, the first two and the test data
flowillg therefrom being directed to a zincate or cyanide-frec bath.

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EXAMPL~ I
A solution of 5.7 mole o te~raethylene pentamine was
reacted with 14.7 mole N-(3-chloro-2-hydroxypropyl) trimethyl
ammonium chloride in the presence of 300 grams of sodium hydroxide.
The solution was refluxed for 1 hour. The product obtained was
then mixed in the amount of 2 g/l with lOg/l of zinc oxide and
100 g/l of sodium hydroxide. Using a conventional Hull cell with
the above described plating solu~ion maintained at a temperature
of about 70F., steel panels measuring approximately 3 by 5 inches
were plated in the bath just described for about ten minutes at 2
amperes. I'he zinc deposit obtained was uniform and semi-bright.
~.
EXAMPLE II
A solution of 1 mole triethylene tetramine containing 250
grams sodium hydroxide was reacted with 3 moles of N-~3 bromo-2
hydroxy propyl) trimethyl ammonium bromide by refluxing for one
hour. The resulting product was mixed in the quantity of 4 g/l
with 10.5 g/l of zinc metal and 90 g/l of sodium h~droxide. Plating
was accomplished in a Hull cell at about 80F. for approximately
10 minutes at one ampere. An even, semi-bright zinc deposit
was obtained.
F.XAMPLE III
The resulting product obtained from the two s~arting
in~redients mentioned in Example I was mixed in the amount oE
0.5 g/l with 7.5 g/l o zinc metal, 120 g/l o~ sodium hydroxide
and 10 mg/l of betaine o~ benzyl chloride and nicotinic acid,
Again in a Hull cell maintained this time at about 90F. and a
~lating time of approximately ten minutes at 2 amperes, the zinc
deposit obtained was observed to be lustrous over a wide current
density range.

EXAMPLE IV
The resulting product obtained from the reaction o~
the two starting ingredients set forth in Example II was mixed
in the amount of 1 g/l with 6 g/l of zinc metal, 80 g/l of
sodium hydroxide and 100 mg/l of anisaldehyde bisulfite. Under
conditions in a Hull cell of about 75F. and a plating time of
approximately 10 minutes at 2 amperes, the bath of this example
provided a zinc deposit lustrous up to 50 ASF and uniformly
semi-bright above that range.
To illustrate the invention further, there will now
be described work performed with a cyanide zinc bath embodying
the novel concepts of this invention.
EXAMPLE V
To a solution containing 5.7 moles of tetraethylene
pentamine there was added 14.7 moles of sodium hydroxide and
14.7 moles of N-~3-chloro-2-hydroxy propyl~ trimethyl ammonium
~: :
chloride. The solution was heated to 90. ~or one hour and
allowed to cool overnight.
The resultant products were further formulated with
a source of zinc ions and cyanide. The results thereof are set
forth below.
~X~MPLE VI
The compound of Example V in the amount of 1.0 g/l
was mixed with 34O0 g/1 of zinc metal, 75.0 g/l of sodium
hydroxide, and 90.0 g/l oE sod:Lum cyanide~ In a Hull cell, at
room temperature and with 2 amperes on test plates of the dimen-
sions earlier indicated, there was obtained a zinc plate deposit
which was bright below a~out 20 ASF and semi-bright above this
value.
EXAMPLE VII
In a further formulation, the compound of Example V
~,~ .

'7
in the amount of 0.5 g/l was combined with 18~0 g/l of zinc metal,
75 g/l of sodium hydroxide and 45.0 g/l of sodium cyanide. Under
room temperature conditions and 2 amperes in the cathode panel
in a conventional Hull cell, the zinc deposit obtained was
bright below 25 ASF and semi-bright thereabove.
ExAMæLE VIII
An additional formulation was prepared using the
composition of Example V in the amount of 50 mg/l and zinc metal
7.5 g/l, sodium hydroxide 67 g/l, and sodiurn cyanide 11.0 g/1~
On test plates of the approximate dimensions earlier indicated,
the zinc deposit obtained in a Hull cell under room temperature
conditions with 2 amperes in the cathode, the deposit was bright
below about 18 ASF and semi-bright above this curren-t density.
EXAMPLE IX
. _
The composition as prepared in accordance with Exarnple
V was mi~ed in the amount of about 2.0 g/l with 11.5 g/l of
zinc metal, 90.0 g/l of sodiurn hydroxide and 3.75 g/l of sodium
cyanide. In a Hull cell the zinc deposit was bright below 35 ASF
and generally semi-bright above 35 ASF~ The deposi-t was plated
at roorn temperature with 2 amperes on -the cathode.
As was stated hereinabove, one of the inventive
contributions made by the instant applicants is the discovery
that by utilizing a small chain reaction product of a poly-
alkylene amine having a molecular weight in the range oE 60 to
1000 with an organic ammoniurn halicle containing a halide capable
of q~aternizing or all~ylating a ni-trogen oE the polyal~ylene
amine so as to produce a plurality oE nitrogen quaternary
sites, there ~ achieved substantially improved results by way
of plating solution stability as well as ductility and brightness
of the zinc deposits. In order to more fully illustrate this
advance over the inventive concept set forth in commonly assigned
- 10 ~
~'4 ~:

3~7
Patent ~o. 3,853,718, the following comparative data was
developed in an essentially cyanide-free zinc electroplating
bath.
An alkaline zinc electroplating solution was prepared
containing zinc metal in the amount of abou-t 6.8 g/l and
approximately 80 g/l of sodium hydroxideO This solution was
divided into two essentially equal portions and to Part (A)
there was added 2 g/1 of a multi-nitrogen compound derived from
a polyal~ylene imine having a molecular weight of about 100 9 000
and N-(3-chloro-2-hydroxy propyl) trimethyl arnmonium chloride.
To Part (B) there was added 2 g/l of a multi-nitrogen compound
derived from a polyalkylene amine whose molecular weight was
about 190~
In a conventional ~Iull cell, operated at approximately
70F., with 2 amperes on the cathode, the following results
were obtained after 30 minutes on the normally used steel plates.
Both Part (A) and (B) under the conditions stated produced
bright zinc deposits, however, the deposit o-f Part (A) was less
ductile -than that obtained ~rom Part (B). On the other hand,
after a lengthy period of plating and the addition of ]~nown
brighteners to the solutions containing Parts (A) and (B), there
was observed a tendency w:Lth solution (A) toward dullness in
the high current density areas apparently due to interference
of brea~-down products. In low c:urrent density areas, the Part
(B) solution was more clear and of greater brigh-tness than that
of solution (A).
Various changes and modiEications in the Eormulations
herein disclosed and in the method of compounding the same may
of course be practiced without departing from the spirit of the
invention or the scope of the subjoined claims.
.