Note: Descriptions are shown in the official language in which they were submitted.
~343~7
BACKGROUND OF THE INV:E:NTI ON
::
Because of its effectiveness and comparatively low cost,
zinc plating has received wide spread commercial application for
the corrosion protection of ferrous substrates and also as a deco~
rative finish. Zinc electroplating baths and processes of the
types heretofore ]cnown have incorporated various brighteners to
enhance the brightness of the deposited zinc plate further enhanc-
ing the appearance of the plated article. While such prior art
compositions and techniques have been effective in producing re-
latively bright zinc deposits, a continuing problem has been the
lack of achieving a desired degree of leveling or smoothness of
the deposit. This problem is further aggravated by the fact that
such bright zinc deposits are frequentIy applied on surfaces of ~ ;
articles which are relatively unfinished, rough and uneven thereby `
further magnifying surface roughness.
The improved non-cyanide zinc electropla-ting bath com-
posi-tion and process of the present invention provides for a
leveling heretofore unattainable with l~ath compositions and pro-
cesses previously known, and further provides a smooth, bright
and adherent zinc plating deposit of excellent corrosion and
aesthetic appearance.
SUMM~RY OF THE INVENTION "~
The benefits and advantages of the present invention
are achieved by a non-cyanide zinc electroplating bath composition
of the so-called acid or neutral type adapted to operate over a ~-
pH range of from about 2.0 to about 9.0 which contains a controlled
e-Efective amount of a leveling and brightening agent comprising a -
.~
bath soluble butyl nicotinate quaternary salt of the formula: -~
~ '.
~2- ` :
,
-
~l~a3~
o l+
~ .C-O~ (~2)3-CH3
.~ . .
_ ' _ :
Wherein.
R is CH3, C2Hs or C6H5CH2~ and
X is Cl, Br, I, R-O-S03 or R-S03
The butyl nicotinate quarternary salts are efEective
when employed in amounts as low as about 0.5 mg/l and can be em `~ .
ployed in concentrations as high as about 10.0 g/l depending upon
the specific bath composition and the presence and concentration
of supplemental supporting agents used.
.
In accordance with a preferred embodiment of the com-
position and process of this invention, the use of the leveling
and brightening agent in acid zinc chloride electroplating baths
i~ further enhanced by the addition of controlled amolmts of
p~l~ethe.rs as a supporting brightener agent and controlled effec-
tive amounts of methane sulfonic acid and the salts thereof as a
supplemental supporting leveling agent~ When operating the zinc
plating bath at pM I5 generally above about 6.8, an organic
chelating agent is advantageously incorporated to prevent zinc
metal from precipitating from the bath.
In accordance with the p.rocess aspects of the present
invention~ smooth, bright and adherent zinc deposits on metal
substrates are attained by subjectin~ the articles to a electro-
plating bath composit;on incorporating the aforementionçd butyl
nicotinate quaternary salt at temperatures rang.inc~ from about
-3-
~3~3~
60F to about 140F and at current densities broadly ranging from
about 5 ASF up to about 200 ASF.
Additional benefits and advantages of the present inven- ;
tion will beeome appa.rent upon a reading of the description of ;
the preferred embodiments taken in conjunction with the specific
examples herein provided.
DESCRIPTION OF THE PRE:FERRED EMBODIMENTS
The improved electroplating bath of the present inven~
tion comprises an aqueous, cyanide-free, neutral or acid-type -~
zinc electroplating bath having a pH ranging from about 2.0 up
to about 9.0 ineorporating the hutyl nicotinate quaternary salt
in an ef~ective amount in addition to appropriate amounts of
other eonventional constituents employed in acid zinc baths. In
aecordanee with eonventional praetice, the bath comprises an .
a~ueous solution containing an aqueous soluble zine ~alt, sueh
as zinc sulfate, zinc chloride, zinc fluoroborate, zinc aeetate ~ :
or the like às well as mixtures thereof to provide a eoncentration
of z.ine rangin~ from about 5.0 up to approximately 105 g/l with
. .
eoneentrations of æinc from about 5.0 to about 70 g/l being pre-
f~rred.
In accordance with conventional practice, the aqueous
soll:ltion may further contain inert salts from improving the con-
ductivity o~ the bath sueh as sodium ehloride, potassiwll chloride, ` ~:~
ammonium ehloride, ammonium sulfate, magnesium chloride, magnesium
su1fate and the like which are employed in concentrations ranging
from about l.Q g/l up to approximately 500 g/l. In addition to
the foregoing any one of a variety of wetting agents in accordance ~-
with conventional practice ean also be satisfactorily employed with -;
eoncentrations thereof typically ranging from about 0.1 up to .
about 30 g/l. Buffering agents of the types also con~entionally -``
employed in commercial practice can al50 be advantageously ~.
,
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employed such as boric acid or i.ts salts, acetic acid on its salts,
or like compounds which are typically present in concentrations
of from about 0.5 up to approximately 100 g/l.
In addition to the foreyoing conventional constituents,
the improved bright zinc electroplating bath incorporates a con-
trolled effective amount of a leveliny and brlghtening agent com-
prising a butyl nicotinate quaternary salt of the formula:
_ _
: :
- ~C~ -C~3 X-
_
Wherein:
R is CH3, C2Hs r C6~15CH2' and
X is C1, Br, I, R-0-503 or R-503 .
The butyl nicotinate quaternary salt as the primary
l~v~llnc~ and brightening agent is employed in concentrations as
low as about 0.5 mg~l to amounts as high as about 10 g/l, while .
concentrations ranginy from about 10 my/1 to about 100 mg/l are
pre:Ee:rred in most instances. Included among the primary leveling
ayents which have prov.ided satisfactory performance are butyl
nicotinate benzyl chloride quaternary, butyl nicotinate dimethyl ~ ~
sulfate quaternary, butyl nicotinate methyl methane sulfonate ~-
quaternary, butyl nicotinate methyl iodide quaternary, butyl .. :
nicotinate ethyl iodide quaternary, butyl nicotinate methyl
chloride quaternary, butyl nicotinate ethyl bromide quaternary,
butyl nicotinate di.ethy1 sullate quaternary, and butyl nicotinate
p-metllyl tosylate ~uaternary.
,
. ~5 ~.
1.3~3~
In addition to the primary leveling and brightening ; `
agent, the aqueous plating solution can advantageously contain
secondary or supporting brighteners such as a polyether having a .~
molecular weight ranging from about 100 up to about 1,000,000 and ~ ;
selected from the group consisting o polyalkylene glycols, poly-
ethylene glycols, polypropylene glycols, polyglycidols,ethoxylated
phenols, ethoxylated naphthols, ethoxylated acetylenic glycols,
ethoxylated ~le~in glycols, and mixtures thereof. The secondary
brightener can advantageously be employed in amounts ranging from ~.
about 0.25 up to approximately 20 g/l. Particularly satisfactory
xesults have been obtained in acid zinc chloride plating baths
employing a secondary polyether brightener comprising acetylenic
gl.ycol 2,3,7,9 -tetramethyl -5-decyne-4, 7 diol-ethoxylated, or
ethoxylated naphthol.
The improved leveling attained by employing the primary ~-~
leveling agent oan stlll be further enhanced in most instances
by incorporating controlled effective amounts of methane sulfonic :
acid~as well as salts thereof includlng sodium salt, potassium
salt, ma~nesium salt, zinc salt, and the like. The secondary
methane sulfonic acid l.eveling agent can be employed in amounts
rancJilly from about 0.005 up to about 5.0 g/l while concentrations
of about 0.05 to about 0.02 g/l are satisfactory in most instances.
The pH operating range from about 2.0 to about 9.0 of
the plating bath can be adjusted by the addition of sulfuric acid
to the sulfate, sulfate-chloride, and hydrochloric acid to the
chloride bath which is facilitated by the addition of conventional .
bu~fering agents thereto. In si-tuati.ons where the bath pH operat~ ~ .
ing range is above about 6.8, a sui.table organic chelating agent
is advantageously employed such as NTA, ~DTA, citric acid, or the :
like in amounts conventionally ranging from approximately 0.5 up
to about 250 g/l for preventing the zinc metal ions from p.recipi-
~ ~ 3,~3~ ~7
tating out of the bath.
The advantages of the bath composition of the present ~`
invention are attainable in accordance with its process aspects
employing barrel, tank as well as continuous plating facilities
and equipment. The bath solution can be satisEactorily employed
at temperatures ra~ging from about room temperature up to about
140F with temperatures of from about 60F to about 90F usually
being preferred.
In order to further illustrate the present invention,
the following specific examples are provided. It will be under-
stood that the examples are provided for illustrative purposes
and are not intended as being restrictive of the present invention
as herein described and as set forth in the subjoined claims.
EXAMPLE 1
A J-shaped steel test specimen is plated for a period `~
of 15 minutes at a current density of 40 ASF employing a bath com-
position as follows:
ConstltuentConcelltrstL_ r
ZillC chloride 60
potassium chloride 195
boric acld 30
2,3,7,9 te~ramethyl 5-decyne
~, 7 diol 30 moles ethoxylated 5
butyl nicotinate dimethyl
sulfate quaternary 0O06
The pH of the plating bath is 5.8. The ~-shaped steel
test specimen upon completion of platin~ is provided with a
smooth uniEorm bright zlnc electrodeposit.
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EX~MPLE 2
A J-shaped steel test specimen is electroplated at a
current density of 30 ASF for a period of 20 minutes in a bat.h
composition having a pH of 5.5 as follows:
ConstituentConcentration g/l
zinc chloride 5
ammonium chloride 100 -:~
ethoxyla-ted B-naphthol
(avg. MW 900) 10
butylnicotine benzyl . ..
chloride quaternary . 0.015 -
The electroplated specimen has a smooth bright zinc
el~ctrodeposit on the surface thereof.
EXAMPLE 3
A J~shaped steel test specimen is electroplated in a -
bath at a temperature of 78F at a current density o~ 25 ASF for
a period o about 30 minutes. The bath has a pH o 5.2 and a~ .
composition as follows: ..
Constituent Concentxation g/l
zinc sulfate 10
zinc chloride .25
ammonium chloride. 224
polyethylene glycol -
(MW 1000) 2 ~ :
butyl nicotlnate ethyl :`~
bromide quaternary 0.05
. At the completion of the electroplating the test speci~
men was observed as having a smooth adherent bri~ht ~inc electro-
deposit thereover.
While it wi.ll be apparent that the invention herein
disclosed is well cal.culated to achieve the beneflts and advan-
tac~es as hereinabove set ~orth, it will be appreciated that the
inve~ltion is susceptible to modification, variation and chan~e
3~ `
without departing from the spirlt thereof.
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