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Патент USA US3041267

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3,041,257
Patented June 26, 1962
2 .
Chromium electroplating baths can be prepared by
supplying CrO3 in the form of chromic anhydride or in
CHRQMIUM ELECTROPLATING
the form of compounds containing cations which do not
Richard P. Cope, Jan‘, Wilkinsburg, and John R. Drobne,
Munhall, Pa., assignors to Westinghouse Electric Cor
affect adversely the bath characteristics. Such com
poration, East Pittsburgh, Pa., a corporation of Penn 5 pounds include the chromates, dichromates, and poly
sylvania
chromates of potassium, sodium, magnesium and cal
No Drawing. Filed Aug. 25, 1960, Ser. No. 51,770
cium. The CrO3 can be added in the form of chromic
11 Claims. (Cl. 204-‘—51)
acid and/or dichromic acid in solution. Where alkali
r
3,041,257
‘
‘
metal cations are present, the bath should not be neutral
This invention relates to the electrodeposition of chro
ized
in excess of 80% of the dichromate end-point.
mium from aqueous acidic hexavalent chromium baths
Sulfate
‘ions can be added in the form of sulfuric acid
(and has particular reference to aqueous acidic hexavalent
as above set forth or as a sulfate salt or salts with a
chromium baths comprising a stable additive composition
cation that does not affect adversely the characteristics
for the bath which is capable of reducing substantially
of the bath. Examples of such cations include potassium,
the formation of spray and mist during‘ electrolysis.
15 sodium, calcium, strontium, magnesium, and chromium.
It is well known in the art that large quantities of hy
Silico?uoride ions can be added to the bath to main
drogen are evolved at the cathodes and large‘quantities
tain
and to regulate the catalyst acid radical content
of oxygen and ozone are evolved at the insoluble anodes
of the bath. Silico?uoride ions can be added in the form
during the electrodeposition of chromium from aqueous
acidic hexavalent chromium solutions or baths. An un 20 of ?uosilicic acid. Also, they can be added as silico
?uoride salt or salts with a cation that does not affect ad
desirable spray and mist of chromic acid is given off from
versely
the bath characteristics such as potassium, sodium,
the bath as the-many gasfbubbles formed by the relatively
large quantities of hydrogen, oxygen and ozone burst
magnesium, and chromium.
The silico?uoride ion is
usually‘ present in an amount equal to about 1% to 2%
, The spray and mist that is given oil? during electrolysis 25 of ‘the chromic acid concentration. .
The examples below are illustrative of typical bath
is of considerable volume, and is highly toxic ‘to the
formulations.
workers in and around the area of the spray. {Further
Example I
violently at the. surface of the bath.
_ '
>
_
more, the mist is highly corrosive to nearby equipment,
and has a deleterious contaminating effect on other plat
ing baths in the vicinity.
Many attempts have been made by those skilled in
the art to prevent or to minimize substantially the forma
v
Ounces per gallon
30 Chromic acid (CrO3) ________________ __
27 to 67
Strontium sulfate ___________________ __ 0.8-1 to 2.01 ~
Potassium silico?uoride ______________ __ 2.16 to 5.36
tion of this highly undesirable spray- and mist during
Example II
_
the electrodeposition of chromium from aqueous acidic
Chromic
acid
(CrO3)
______________________
__
40
hexavalent chromium solutions. The methods proposed 35
Sulfuric acid ______________________________ __ 0.24
heretofore have not been entirely satisfactory.
Fluosilicic acid; ___________________________ __ 0.40
This invention is concerned particularly with provid
ing a stable additive composition for acidic hexavalent
The stable additive compositions of this invention are
chromium baths which is capable of minimizing substan—
soluble in conventional aqueous acidic hexavalent chro
tially the formation of spray and mist during electrolysis 40 mium baths and will prevent or minimize effectively the
of such baths with insoluble or highly polarized anodes,
formation of spray and mist. Furthermore, the addi
and to provide a new and improved hexavalent chromium
tive compositions are stable'to the extremely powerful
plating bath.
oxidizing conditions that exist at the insoluble anodes
For a complete understanding of this invention, refer
during the electro-deposition of chromium from such
ence is made to the following detailed description.
45 baths.
In accordance with this invention stable additive com
The stable additive composition of this inventioncom
positions for aqueous acidic hexavalent chromium elec
prises speci?c non-ionic wetting agents alone or in ad~
troplating baths have been found that are highly satis
mixture with certain alkyl aromatic sulfonates to be
factory in preventing substantially the formation of spray
detailed more fully hereinafter. The non-ionic wetting
and mist during electrolysis.
'
,
Chromiumgelect'ropolating baths ‘are well known in
the art, and basically they comprise chromium trioxide,
C103, chrornic acid or chromic anhydride, Water, and
50 agents or surfactants are selected from the group consist~
ing of (1) polymers of ethylene oxide having an aver
age molecular weight of from about 1,300 to 1,800, (2)
a cogeneric mixture of conjugated polyoxypropylene
polyoxyethylene compounds containing in their structure
a catalyst. There would be no chromium deposited
from the bath without the catalyst. The addition of a 55 oxypropylene groups, oxyethylene groups and ‘van or
suitable catalyst in the ratio of about 1 part by Weight
ganic radical derived from an organic compound con
to 100 parts by weight of chromic acid produces a satis
factory working solution. The above ratio can be varied
to meet different plating conditions. Thus, the ratio has
been varied by those skilled in the art from about 1:60
taining a plurality of reactive hydrogen atoms, the com
pounds being characterized in that all of the oxypropylene
to
hydrogen atom to thereby constitute a polyoxypropylene
polymer, the oxyethylene groups are attached to the poly
1:250.
'
V
The catalyst'employed in the chromium electroplat
ing bath can be a sulfate, usually introduced into the
bath: by the addition of sulfuric acid.
groups are present in polyoxypropylene chains that are
attached to the organic radical at the site of a reactive
oxypropylene polymer in polyoxyethylene chains, the
average molecular weight 'of the polyoxypropylene poly
Sorhe common formulations are as follows: (i) 33 65 mer in the mixture is within the range of from about
‘ounces of chromic acid per gallon of electrolyte and 0.33
ounce of sulfuric acid (98%) per gallon of electrolyte;
(ii) 54 ounces of chromic acid per gallon of electrolyte
and 0.54 ounce of sulfuric acid (98%) per gallon of
electrolyte; and (iii) 40 ounces of chromic acid per gal
lon of electrolyte and 0.40‘ ounce of sulfuric acid (98%)
gallon of electrolyte.
1,500 to 1,800, as determined by hydroxyl number, and
the oxyethylene groups present constitute from about
80% to 95% by weight of the mixture, and (3) mixtures
of (1) and (2).
'
Nonionic Wetting agent (2) above can be represented
by the structural formula
3,041,257
3
tinued at room temperature for 2 hours. The sulfona
tion mixture is drowned in four times its weight of a mix
ture of ice and water and a solution of sodium hydroxide
wherein Y represents an integer su?'icient to provide a
molecular weight of polyoxypropylene of from 1500 to
1800, and X and Z are in integers the total of which
is su?icient to provide oxyethylene groups in an amount
equal to from about 80% to 95% ‘by Weight of the total
is added while keeping the temperature below 35° C.
until the product is neutral (pI-l=7.0). The neutralized
solution is evaporated to dryness to provide an alkyl
weight of the molecule.
Compounds of the types above described under (2)
are available commercially under the proprietary desig
aromatic sulfonate of the benzene series suitable for use
in this invention.
The amount of stable additive (composition of this in
nation “Pluronic.”
_
It has been determined also, according to the present 10 vention that is added to the chromium electroplating bath
will be suf?cient to provide a bath surface tension of at
invention, that substantial reduction of the undesired
least 55 dynes per cm.2 at 25° C. It has been deter
chromic acid spray can be accomplished by adding to
mined that the stable additive composition of this in
the bath an admixture of from 10 to 90 parts by weight
vention, Whether it comprise the above de?ned nonionic
of the above enumerated nonionic wetting agents (1),
wet-ting agents alone or the nonionic wetting agents in
(2), and (3) and from 90 to 10 parts by weight of an
admixture with the alkyl aromatic sulfonates of the ben
alkyl aromatic sulfonic acid compound of the benzene
zene series, can be‘ added in amount ‘of from about .015
series containing at least 7 carbon atoms in an alkyl
to .40 ounce per gallon of electrolyte. \It is within the
skill of those versed in the art to determine the amount
and (3) enumerated above are effective in reducing sub 20 of additive composition'required to provide a bath sur
face tension of at least 55 dynes per cm.2 at 25° C., or
stantially the chromic acid spray, it is preferred to em
group.
»
While the speci?c nonionic wetting agents (1), (2),
at least an amount suf?cient to retard substantially the
ploy the admixture as set forth hereinbelow as it is even
liberation of chromic acid fumes or spray from the bath.
more eifective. The preferred admixture will comprise
The non-ionic wetting agents alone provide for sub
from 40 to 60 parts by Weight of nonionic rwet-ting agent
(1), (2), or (3) and ?om 60 to 40 parts by weight of 25 stantial reduction of the surface tension of the chromium
electroplating bath and is satisfactory for most baths.
alkyl aromatic sulfonic acid compound of the benzene
However, for baths of higher chromic acid concentration
series containing at least 7 carbon atoms in an alkyl
it is preferred to employ the admixture of non-ionic wet
group.
ting agent acid alkyl aromatic sulfonates as above de
Alkyl aromatic sulfonic acid compounds of the ben
zene series containing at least 7 carbon atoms in an alkyl 30 ?ned as the surface tension of the bath is more elfectively
controlled thereby eliminating substantially any undesired
group can be represented by the formula
i
chromic acid spray.
The examples that follow are illustrative of this in
vention.
$03M
in which X represents hydrogen; a hydroxyl group; a
Example IV
To a chromic acid ‘bath containing 54 ounces of CrO;
carbon atoms, and M represents hydrogen or a metal,
from an organic compound containing a plurality of re
35
per gallon of aqueous solution and a ratio of HSO4:CrO3
lower alkyl group such as methyl, ethyl, propyl, isopropyl,
within the range of 1:100 there is added .20 ounce per gal
and n-butyl; analkoxy group such as methoxy, ethoxy,
benzyloxy and the like; an aryloxy group such as phen 40 lon of a non-ionic wetting agent consisting of a cogeneric
mixture of conjugated poloxypropylene-polyoxyethyl
oxy and methylphenoxy; or a carboxyl group. R rep
ene
compounds containing in their structure cxyproylene
resents an alkyl hydrocarbon radical (saturated or un
groups, oxyethylene groups and an organic radical derived
saturated) containing 7 or more (preferably 10 to 19)
For
active hydrogen atorns, the compounds being character
Reference is made to US. Patent 2,195,409 for a
by constitute a polyoxypropylene polymer, the oxyethyl
or an ammonium or an organic ammonium radical.
convenience this'class of compounds will be referred to 45 ized in that all of the oxypropylene groups are present in
polyoxypropylene chains that are attached to the organic
hereinafter as “alkyl aromatic sulfonates of the benzene
radical at the site of the reactive hydrogen atom to there
series.”
‘
ene groups are attached to the polyoxypropylene polymer
more detailed description of alkyl aromatic sulfonates
of the benzene series, speci?c examples thereof, and 50 in polyoxyethylene chains, the average molecular weight
of the polyoxypropylene polymer in the mixture is about '
methods of‘ preparing the same.
1500 to 1800 as determined by hydroxyl number, and the
The following speci?c example is given by way of illus
oxyethylene groups present constitute about 80% by
tration. All parts are by weight unless otherwise desig
weight of the mixture. During operation of this bath, sub
nated.
Example III
One hundred parts of commercial lauryl alcohol (ob
tained by hydrogenation of ‘fatty acids from cocoanut
oil), 100 parts of phenol, and 100 parts of anhydrous
55 stantially no chromic acid spray or mist is noted.
Example V
Achromium plating bath is prepared as described in
Example IV above except that 40 ounces of CrO3 are em
zinc chloride ‘are mixed and re?uxed at 190° C. to 200° 60 ployed per gallon of solution and .20 ounce per gallon
C. with agitation for about 16 hours. The condensa
tion product is washed with water until substantially free
of water-soluble products, and the resulting oil is frac
tionally distilled in vacuo. The fraction of the distillate
of a polymer of ethylene oxide having a molecular weight
of about 1500. Excellent results are obtained in plating
various types of objects in this bath and there is sub
stantially no chromic acid spray or mist noted.
collected as a faint yellow to water-white oil between 65
To the chromium plating bath of Example II there is
210° C. to 230° C. at 13 mm. mercury pressure consists
added about .30 ounce per gallon of a stable additive
mainly of lauryl phenols of ‘which the probable formula
of the main constituent is
(1101121
composition consisting of, by weight, 5 0 parts of the non
ionic Wetting agent used in Example IV and 50 parts of
the alkyl aromatic sulfonate of the benzene series of
70 Example III. Good plating results are obtained and no
objectionable chromic acid spray is noted.
The operating conditions for the bath ‘of this invention
One houndred twenty-two parts of ‘chlorosulfonic acid
are the same as those employed for the baths without the
addition of the stable additive composition of this inven
are added to 270 parts of the resulting oil which is held
at a temperature below 10° C., then sulfonation is con 75 tion. Thus, operating temperatures of from about 100°
3,041,257
5
C. to 160°’ C. can be employed, and current densities of
from about 100 to 500 amperes per square foot are
satisfactory.
A signi?cant reduction in the spray and mist formed
during electrodeposition of chromium from aqueous acidic
hexavalent chromium baths is apparent when the additive
composition of this invention is employed. Further the
additive compositions of this invention are very stable.
That is they do not decompose in the chromium bath and
lose their effectiveness.
,
6
ture oxypropylene groups, oxyethylene groups and an
organic radical derived ‘from an organic compound con
taining a plurality of reactive hydrogen atoms, the com
pounds being characterized in that all of the oxy-propyl
ene groups are present in polyoxypropylene chains that
are attached to the organic radical at the site of the re
active hydrogen atom to thereby constitute a polyoxypro
pylene polymer, the oxyethylene groups are attached to
the polyoxypropylene polymer in polyoxyethylene chains,
the average molecular Weight of the polyoxypropylene
polymer in the mixture being from about 1500 to 1800
as determined by hydroxyl number, and the oxyeth
thereof.
F
ylene groups present constitute from about 80% to
We claim as our invention:
95 % by weight of the mixture, and (3) mixtures of (l)
1. A chromic acid plating bath for the electrodeposition 15 and (2), and (B) from 60 parts to 40 parts by weight
of chromium comprising an aqueous acidic hexavalent
of an alkyl aromatic sulfonic acid compound of the ben
chromium solution containing a non-ionic wetting agent
zene series containing at least 7 carbon atoms in an alkyl
selected from the group consisting of (1) polymers of
group, said stable additive composition being present in
ethylene oxide having an average molecular weight of
an amount su?icient to retard substantially the liberation
from 1300 to 1800, (2) a cogeneric mixture of conjugated 20 of chromic acid fumes from said bath.
‘
polyoxypropylene-polyoxyethylene compounds contain
4. The method of chromium plating which comprises
a ing in their structure oxypropylene groups, oxyethylene
electrodepositing chromium from a chromic acid plating
groups and an organic radical derived from an organic
bath comprising a non-ionic Wetting agent selected from
compound containing a plurality of reactive hydrogen
the group consisting of (1) polymers of ethylene oxide
atoms, the compounds being characterized in that all of 25 having an average molecular weight of from 1300 to
the oxypropylene groups are present in polyoxypropylene
1800, (2) a cogeneric mixture of conjugated polyoxy
It is to be understood that the above description of
this invention is illustrative only and not in limitation
chains that are attached to the organic radical at the site
of ‘a reactive hydrogen atom to thereby constitute a poly
oxypropylene polymer, the oxyethylene groups are at
propylene~polyoxyethylene compounds containing in
tached to the polyoxypropylene polymer in polyoxye'thyl
ene chains, the average molecular weight of the polyoxy
propylene polymer in the mixture being from about 1500
to 1800 as determined by hydroxyl number, and the oxy
pound containinga plurality of reactive hydrogen atoms,
ethylene groups present constitute from about 80% to
their structure oxypropylene groups, oxyethylene groups
and an organic radical derived from an organic com
the compounds being characterized in that all of the
oxypropylene groups are present in polyoxypropylene
chains that are attached to the organic radical at the site
of the reactive hydrogen atom to thereby constitute a
95% by Weight of the mixture, and (3) mixtures of (l) 35 polyoxypropylene polymer, the oxyethylene groups are
and (2), said non-ionic Wetting agent being present in an
attached to the polyoxypropylene polymer in polyoxy
amount su?icient to retard substantially the liberation of
ethylene chains, the average molecular Weight of the
chromic acid fumes from said bath.
'
polyoxypropylene polymers in the mixture is from about
2. A chromic acid plating bath for the electrodeposition
1500 to 1800 as determined by hydroxyl number, and
‘ of chromium comprising an aqueous acidic hexavalent 40 the oxyethylene groups present constitute from about
chromium solution containing a stable additive composi
tion comprising (A) from 10 to 90 parts by Weight of a
non-ionic Wetting agent selected from the group consist
ing of (l) polymers ‘of ethylene oxide having an average
molecular weight of from 1300 to 1800, (2) a cogeneric
80% to 95% by Weight of the mixture, and (3) mix
tures of (1) and (2), said nonionic wetting agent being
present in an amount su?icient to retard substantially
the liberation of chromic acid vfumes from said bath.
45
5. The method of chromium plating which comprises
mixture of conjugated polyoxypropylene-polyoxyethylene
electrodepositing chromium from a chromic acid plating
compounds‘ containing in their structure oxypropylene
bath comprising a stable additive composition comprising
groups, oxyethylene groups and an organic radical derived
(A) from 10 to 90 parts by weight of a non-ionic wetting
from an organic compound‘ containing a plurality of re
agent selected from the group consisting of (1) polymers
active hydrogen atoms, the compounds being character
of ethylene oxide having an average molecular Weight of
ized in that all of the oxypropylene groups are present in
from about 1300 to 1800, (2) a cogeneric mixture of
polyoxypropylene chains that are attached to the organic
conjugated polyoxypropylene-polyoxyethylene compounds
radical at the site of the reactive hydrogen atom to thereby
‘containing in their structure oxypropylene groups, oxy
constitute a polyoxy-propylene polymer, the oxyethylene
ethylene groups and an organic radical derived from an
groups are attached to the polyox-ypropylene polymer in
organic compound containing a plurality of reactive hy
polyoxyethylene chains, the average molecular weight of
the polyoxypropylene polymer in the mixture being from
about 1500 to 1800 as determined by hydroxyl number,
‘ and the oxyethylene groups present constitute from about
drogen atoms, the compounds being characterized in that
all of the oxypropylene groups are present in polyoxy
propylene chains that are attached to the organic radical
at the site of a reactive hydrogen atom to thereby con
80% to 95% by Weight of the mixture and (3) mixtures 60 stitute a polyoxypropylene polymer, the oxyethylene
of (1) and (2), and (B) from 90 parts to 10 parts by
groups are attached to the polyoxypropylene polymer in
Weight of an alkyl aromatic sulfonic acid comwund of
polyoxyethylene chains, the average molecular Weight of
the benzene series containing at least 7 carbon atoms in an
the polyoxypropylene polymer in the mixture being
1 alkyl group, said stable additive composition being present
Within the range of from about 1500 to 1800 as deter-,
, in van amount su?icient to retard substantially the liberation
of chromic acid fumes from said bath.
3. A chromic acid plating bath for the electrodeposi
tion of chromium comprising an aqueous acidic hexa
valent chromium solution containing a stable additive
composition comprising (A) from 40 to 60' parts by
Weight of a non-ionic lwetting agent selected from the
group consisting of (1) polymers of ethylene oxide hav
ing an average molecular Weight of from 1300 to 1800',
(2) a cogeneric mixture of conjugated polyoxyproply
mined by hydroxyl number, and the oxyethylene groups
present constitute from about 80% to 95% {by Weight
of the mixture, and (3) mixtures of (1) and (2), and
(B) from 90 parts to 10 parts by :weight of an alkyl aro—
matic sulfonic acid compound of the benzene series con
taining at least 7 carbon atoms in an 'alkyl group, said
'stable additive composition being present in an amount
su?‘icient to retard substantially the liberation of chromic
acid fumes from said bath.
'
6. The method of chromium plating Which comprises
ene-polyoxyethylene compounds containing in their struc 75 electrodepositing chromium from a chromic acid plating
3,041,257
0
bath comprising a stable additive composition comprising
polyoxypropylene polymers in the mixture being from
(A) from 40 to 60 parts by weight of ‘a non-ionic Wet
about 1500 to 1800 as determined by hydroxyl number,
and the oxyethylene groups present constitute from about
ting agent selected from the group consisting or" (1)
polymers of ethylene oxide having an average molecular
weight of from about 1300 to 1800, (2) a cogeneric mix
_ 80% to 95% by weight of the mixture, and (3) mix
ture of conjugated polyoxypropylene-polyoxyethylene
compounds containing in their structure oxypropylene
tures of (l) and (2), and (B) from 90 parts to 10 parts
by Weight of an alkyl aromatic sulfonic acid compound
of the benzene series containing at least 7 carbon atoms
groups, oxyethylene groups and an organic radical derived
from an organic compound containing a plurality of re
in an alkyl group said stable additive composition being
ganic radical at the site of a reactive hydrogen atom to
sition of chromium comprising an aqueous solution of
thereby constitute a polyoxypropylene polymer, the oxy
from about 33 ounces to 54 ounces per gallon of C103,
present in an amount su?‘icient to retard substantially the
active hydrogen atoms, the compounds being charac 10 liberation of chromic acid fumes and spray from said
bath.
terized in that all of the oxypropylene groups are present
9. A chromic acid plating bath for the electrodepo
in polyoxypropylene chains that are attached to the or
ethylene groups are attached to the polyoxypropylene 15 an amount of H2804 sui?cient to provide a ratio of
H2SO4:CrO3 of 1:250 to 1:60 and a quantity of a stable
polymer in polyoxyethylene chains, the average molecular
weight of the polyoxypropylene polymer in the mixture
being Within the range of from about 1500 to 1800 as
determined by hydroxyl number, and the oxyethylene
additive composition comprising (A) from 40 to 60 parts
by weight of a non-ionic Wetting agent selected from the
group consisting of (1) polymers of ethylene oxide hav
groups present constitute from about 80% to 95% by 20 ing an average molecular Weight of from about 1300
to 1800, (2) a cogeneric mixture of conjugated polyoxy
weight of the mixture, and (3) mixtures of (1) and (2),
propylene-polyoxyethylene compounds containing in their
and (B) from 60 parts to 40‘ parts by weight of an alkyl
structure oxypropylene groups, oxyethylene groups and
aromatic sulfonic acid compound of the benzene series
an organic radical derived from an organic compound
containing at least 7 carbon atoms in an alkyl group, said
stable additive composition being present in an amount 25 containing a plurality of reactive hydrogen atoms, the
compound being characterized in that all of the oxy
sui?cient to retard substantially the liberation of chrorric
propylene groups are present in polyoxypropylene chains
acid fumes from said bath.
that are, attached to the organic radical at the site of the
7. A chromic acid plating bath for the electro-depo
reactive hydrogen atom to thereby constitute a poly
sition of chromium comprising an aqueous solution of from about 33 ounces to 54 ounces per gallon of CrO3, 30 oxypropylene polymer, the oxyethylene groups are at
tached to the polyoxypropylene polymer in polyoxy
an amount of H280, su?icient to' provide a weight ratio
ethylene chains, the average molecular weight of the
of H2SO4:CrO3 of 1:250 to 1:60 and a quantity of non—
polyoxypropylene polymers in the mixture being from
ionic Wetting agent, selected from the group consisting
about 1500 to 1800 as determined by hydroxyl number,
of (1) polymers of ethylene oxide having an average
molecular weight of from about 1300 to 1800, (2) a 35 and the oxyethylene groups present constitute from about
cogeneric mixture of conjugated polyoxypropylene-poly
80% to 95% by Weight of the mixture, and (3) mix
tures of (1) and (2), and (B) from 60 parts to 40 parts
by weight of an alkyl aromatic sulfonic acid compound
of the benzene series containing at least 7 carbon atoms
radical derived from an organic compound containing a
plurality of reactive hydrogen atoms, the compound being 40 in »an alkyl group said stable additive composition pres
oxyethylene compound containing in their structure oxy
propylene groups, oxyethylenegroups and an organic
characterized in that all of the oxypropylene groups are
present in polyoxypropylene chains that are attached to
the organic radical at the site of a reactive hydrogen
atom to thereby constitute a polyoxypropylene polymer,
the oxyethylene groups are attached to the polyoxy 45
propylene polymer in polyoxyethylene chains, the aver
age molecular Weight of the polyoxypropylene polymers
ent in an amount su?icient to retard substantially the
liberation ‘of, chromic acid fumes and spray from said
bath.
10. A stable additive composition for addition to
chromic acid plating baths whereby the liberation of
chromic acid fumes from said baths during use is re
tarded substantially comprising (A) from 10 to 90 parts
by weight of a non-ionic Wetting agent selected from the
group consisting of (1) polymers of ethylene oxide hav
by hydroxyl number, and the oxyethylene groups present
constitute from about 80% to ‘95% by weight of the mix 50 ing an averagermolecular weight of from 1300 to 1800,
(12) a cogeneric mixture of conjugated polyoxypropyl
ture, and (3) mixtures of (1) and (2) said non-ionic
ene-polyoxyethylene compounds containing in their struc
Wetting agent being present in an amount su?icient to
ture oxypropylene groups, oxyethylene groups and an
retard substantially the liberation of chromic acid fumes
organic radical derived from an organic compound con
from said bath.
taining a plurality of reactive hydrogen atoms, the com
8. A chromic acid plating bath for the electrodepo
pounds being characterized in that all of the oxypropyl
sition of chromium comprising an aqueous solution of
ene groups ‘are present in polyoxypropylene chains that
from about 33 ounces to 54 ounces per gallon of CrO3,
in the mixture is from about :1500 to 1800 as determined
an amount of H2504 su?icient to provide a ratio of
H2SO4:CrO3 of 1:250 to 1:60 and a quantity of a stable
are attached to the organic radical at the site of the re
active hydrogen atom to thereby constitute a polyoxy
additive composition comprising (A) from 10 to 90 parts 60 propylene polymer, the oxyethylene groups are attached
to the polyoxypropylene polymer in polyoxyethylene
by weight of non-ionic wetting agent selected from the
chains, the average molecular weight of the polyoxy
group consisting of (l) polymers of ethylene oxide hav
propylene polymer in the mixture being from about
ing an average molecular Weight of from ‘about 1300 to
‘1500 to 1800 as determined by hydroxyl number, and
11800, (2) a cogeneric mixture of conjugated polyoxy
propylene-polyoxyethylene compounds containing in their 65 the oxyethylene groups present constitute from about
structure oxypropylene groups, oxyethylene groups and ‘ 80% to 95% by Weight of themixture, and (3) mix
tures of (1) and (2), and (B) from ‘90 parts to 10
parts by weight of an alkyl aromatic sulfonic acid com
containing a plurality of reactive hydrogen atoms, the
pound of the benzene series containing at least 7 carbon
compound being characterized in that ‘all of the oxy
propylene groups are present in polyoxypropylene chains 70 atoms in ‘an alkyl‘ group, said stable additive composi
an organic radical derived from an organic compound
that are attached to the organic radical at the site of
the reactive hydrogen atom to thereby constitute a poly
tion being present in an amount sufficient to retard sub
1itantially the liberation of chromic acid fumes from said
ath.
oxypropylene polymer, the oxyethylene groups are at
11. A stable additive composition for addition to
attached to the polyoxypropylene polymer in polyoxy
ethylene chains, the average molecular weight of the 75 chromic acid plating baths whereby the liberation of
3,041,257
chromic acid fumes from said baths during use is retarded
substantially comprising (A) from 40 to 60 parts by
weight of a non-ionic Wetting agent selected from the
group consisting of (1) polymers of ethylene oxide having
an average molecular weight of from 1300 to 1800, (2)
a cogeneric mixture of conjugated polyoxypropylene
polyoxyethylene compounds containing in their structure
oxypropylene groups, oxyethylene groups and an organic
radical derived from an organic compound containing a
plurality of reactive hydrogen atoms, the compounds 10
being characterized in that all of the oxypropylene groups
‘are present in polyoxypropylene chains that are attached
to the organic radical at the site of the reactive hydrogen
atom to thereby constitute a polyoxypropylene polymer,
the oxyethylene groups are attached to the polyoxy 15
propylene polymer in polyoxyethylene chains, the average
molecular Weight of the polyoxypropylene polymer in the
mixture being from about 1500 to 1800 as, determined
by hydroxyl number, and the oxyethylene groups present
10
constitute from about 80% to 95% by Weight of the mix
ture, and (3) mixtures of (1) and (2), and (B) from 60
parts to 40 parts by weight of an alkyl aromatic sulfonic
acid compound of the benzene series containing at least
7'earbon atoms in an ‘alkyl group, said stable additive
composition being present in an amount suf?cient to
retard substantially the liberation of chromic acid fumes
from said bath.
References Cited in the ?le of this patent
UNITED STATES PATENTS
2,115,192
Bruson ______________ __ Apr. 26, 1938
2,195,409
Flett ________ -7 _______ __ Apr. 2, 1940
2,213,477
2,655,471
Steindor?” et al _________ __ Sept. 3, 1940
Chester ______________ __ Oct. 13, 1953
OTHER REFERENCES
“Pluronics,” Wyandotte Chemical Corp., 9 pages, re
ceived in Patent O?ice J an. 7, 1957.
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