U.S. patent number 3,881,919 [Application Number 05/431,025] was granted by the patent office on 1975-05-06 for ternary alloys.
This patent grant is currently assigned to Whyco Chromium Company Inc.. Invention is credited to Jacob Hyner, Robert A. Michelson.
United States Patent |
3,881,919 |
Hyner , et al. |
May 6, 1975 |
TERNARY ALLOYS
Abstract
Bright, tarnish resistant and color stable ternary alloys of
about 40 - 90% of tin, about 10 - 50% cobalt and about 1 - 28% of a
third metal of Periodic Group II.sub.B, III.sub.A or VI.sub.B.
Typical third metals are zinc, cadmium, indium, antimony or
chromium. The alloys are electrodeposited from aqueous acidic baths
at a temperature of about 50.degree. - 85.degree.C. and current
density of about 5 - 45 A/ft..sup. 2. BACKGROUND OF THE INVENTION
This invention relates to new and improved ternary alloys, to
aqueous electrolytic baths from which the alloys are deposited, and
to a process for forming the alloys. Various alloys have been
developed in efforts to duplicate the superior color of chromium
and alloys containing substantial amounts of chromium, while also
providing the corrosion resistance and tarnish resistance required
when the alloy is to be used as a protective coating. Accordingly,
the prior art teaches the addition of brightening agents to plating
baths for the electro-deposition of tin-nickel binary alloys, as in
U.S. Pat. No. 3,141,836 -- Seyb et al, or the careful control of
plating conditions, also in the deposition of nickel-tin binary
allows, such as the highly acidic baths in U.S. Pat. No. 2,926,124
-- Taylor et al. In another approach cobalt-tin binary alloys have
been studied with respect to close similarities in corrosion
resistance to nickel-tin alloys. Clarke et al, "An Electrodeposited
Bright Tin-Cobalt Intermetallic Compound, CoSn," Transactions of
the Institute of Metal Finishing, 1972, Volume 50. Despite the
usefulness of such alloys from the standpoint of tarnish and
corrosion resistance, those of such alloys which initially
exhibited brightness similar to that of chromium did not maintain
the good color. Moreover, results in obtaining hardness,
brightness, tarnish resistance and color stability have not been
consistent. Such properties tend to be overly sensitive to specific
process conditions and therefore are difficult to reproduce on a
commercial scale. OBJECTS AND SUMMARY Accordingly, an object of the
invention is to provide a new and improved alloy which not only
provides a chromium-like brightness and tarnish resistance, but
also provides color stability and hardness superior to that found
in any of the alloying metals individually. Still another object of
the invention is to provide new and improved electrolytic plating
baths which are easily formulated and from which ternary alloys can
be efficiently deposited on a wide variety of substrates to give
coatings which are hard, bright, tarnish resistant and which have
good color stability. Another object is to provide a new and
improved process whereby tin, cobalt and a third metal are
electrolytically co-deposited to form a hard, bright coating which
is stable and highly resistant to tarnishing. These and other
objects, features and advantages of the invention will be apparent
from the description which follows. In summary outline, the
foregoing and other objects are achieved in a new and improved
ternary alloy consisting essentially of about 40 -]90 wt. % tin,
about 10 - 50 wt. % cobalt and about 1 - 28 wt. % of a third metal
selected from Periodic Group II.sub.B, III.sub.A or VI.sub.B. Third
metals include zinc, cadmium, indium, antimony or chromium, of
which zinc, indium and chromium are preferred. The third metals may
be present in the alloy singly or in admixtures of two or more. The
plating baths of the invention are aqueous and highly acidic, and
contain compounds providing stannous ions, cobaltous ions and ions
of the third metal or metals to be deposited. The ternary alloys
are efficiently co-deposited from the baths at a temperature of
about 50 - 85.degree.C. and current density of about 5 - 45
A/ft..sup.2. In addition to the tarnish resistance expected in
alloys containing tin and cobalt, the alloys exhibit a hardness,
chromium-like brightness and color stability which make them useful
as coatings on a wide variety of substrates.
Inventors: |
Hyner; Jacob (Waterbury,
CT), Michelson; Robert A. (Waterbury, CT) |
Assignee: |
Whyco Chromium Company Inc.
(Thomaston, CT)
|
Family
ID: |
23710120 |
Appl.
No.: |
05/431,025 |
Filed: |
January 7, 1974 |
Current U.S.
Class: |
420/562; 205/252;
205/255 |
Current CPC
Class: |
C25D
3/56 (20130101); C22C 13/00 (20130101) |
Current International
Class: |
C25D
3/56 (20060101); C22C 13/00 (20060101); C22c
013/00 () |
Field of
Search: |
;75/175R,175A,134N,134B,134F,170,171 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Rutledge; L. Dewayne
Assistant Examiner: Weise; E. L.
Attorney, Agent or Firm: Delio and Montgomery
Claims
What is claimed is:
1. A bright, tarnish resistant and color stable ternary alloy
consisting essentially of about
40 - 90 wt. % tin
10 - 50 wt. % cobalt
1 - 28 wt. % third metal
wherein said third metal is antimony or a metal of Periodic Group
II.sub.B, III.sub.A or VI.sub.B.
2. A ternary alloy as in claim 1 wherein said third metal is zinc,
cadmium, indium, or chromium.
3. A ternary alloy as in claim 1 wherein said third metal is zinc,
indium or chromium.
Description
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The ternary alloys of the invention are electro-deposited from
highly acidic, aqueous baths of pH of about 1-3. A mineral acid is
utilized for this purpose, such as a hydro-halide or a sulfur acid.
Preferred acids are hydrochloric and fluoboric acids since such
acids provide anions in common with anions of preferred compounds
of the metals to be deposited, and thus promote stability of the
baths and good control of electrodeposition therefrom.
The metals to be deposited are present in the baths as ionic
compounds, the anions of the compounds and other conditions being
chosen such that the compounds are substantially completely soluble
in the aqueous medium. Accordingly, the compounds may be present as
halides, sulfates, or otherwise but preferably the compounds will
have anions common to the anions of the acid utilized to provide
the high acidity. Since hydrochloric and fluoboric acids are the
preferred acids, the preferred metal compounds will be the
chlorides and fluoborates of the metals.
The metal compounds may be dispersed and dissolved in the aqueous
medium in any suitable manner with heating and agitation, as
needed. Sequence of admixture is not critical although the usual
precautions with highly acidic solutions should be exercised.
However, dispersion and electroplating are each benefited by
somewhat elevated temperature of the bath, of the order of about
50.degree. - 85.degree.C.
As chlorides the following ranges of concentrations of the metal
compounds in the baths are effective:
cobalt chloride about 20-400 g./l. stannous chloride about 10-100
g./l. zinc chloride about 10-175 g./l.
To the baths containing the foregoing concentrations of metal
compounds may be added hydrochloric acid (37% solution) at a
concentration of about 40-150 mils./l., ammonium hydroxide (28%
solution) in the range of about 10-50 mls./l. and ammonium
bifluoride, about 20-400 g./l., to provide the requisite acidity
and bath stability.
When the tin compound is a fluoborate, it is preferred to use
fluoboric acid in place of hydrochloric acid. The concentrations of
these and other ingredients in the bath may then range as
follows:
cobalt chloride about 100-300 g./l. stannous fluoborate (50%
solution) about 25-75 mls./l. fluoboric acid about 75-225 g./l.
ammonium hydroxide (28% solution) about 25-150 mls./l. zinc
chloride about 10-135 g./l.
Indium chloride as a substitute for zinc chloride preferably is
utilized at a concentration of about 5 - 35 g./l. and chromium
chloride as a substitute for either of the foregoing compounds is
effective at a concentration of about 5 - 55 g./l.
Other conditions of electrodeposition, including the cell form of
electrolytic arrangement and type of substrate to be coated,
control of concentration and rejuvenation of the baths, are well
known in the art and do not require further description. For
example, the well known Hull cell may be utilized. The current
density preferred for efficient electrodeposition is about 5 - 45
A/ft..sup.2.
Generally, the percentage of each metal in the ternary alloy will
vary in direct proportion to the concentration of each metal in the
plating bath. To a lesser extent the percentage of each metal in
the alloy will also vary in accordance with electroplating
conditions such as temperature, current density and pH. It is
believed that the new alloy exists as Sn.sub.2 (Co, X) or (Sn,
X).sub.2 (Co, X) where X is the third metal.
While the resultant ternary alloys are analogous to tin-nickel and
tin-cobalt with respect to tarnish resistance, the alloys exhibit
not only chromium-like brightness but also consistently good color
and color stability. Moreover, while the ternary alloys resist
corrosion essentially to the same extent as chromium, they have a
higher resistance than chromium to strong alkali under a
superimposed anoidic potential, that is, whereas chromium will
dissolve if made anodic in a caustic solution, the ternary alloys
of the invention are not affected. The alloys of the invention
therefore are more resistant to chloride attack than chromium and
will resist salt spray and salt water contact better than
chromium.
The plating baths may contain auxiliary reagents for various
purposes in accordance with the understanding in the art. Among
such auxiliary reagents are ammonium chloride, gluconic acid,
thiourea, fluorides such as ammonium bifluoride, sodium fluoride
and potassium titanium fluoride, and various surfactants and the
like such as alkyl aryl sodium sulfonate. Such reagents generally
are useful in minor amounts, for example, about 0.01 to about 10
grams per liter of plating bath, to obtain their known
benefits.
The ternary alloys may be co-deposited electrolytically upon a wide
variety of substrates, including metals such as steel, brass and
zinc, as well as ceramics and plastics, in accordance with
techniques well known in the art for coating such substrates.
The following examples of aqueous plating bath formulations and
conditions of electrodeposition are intended as further
illustration of the invention but are not necessarily limited of
the scope of the invention except as set forth in the claims. All
parts and percentages in these examples as well as in the foregoing
specification are by weight unless otherwise indicated. In each
example the ternary alloy deposited has an approximate composition:
tin, 40 - 90%; cobalt, 10 - 50%; third metal, 1 - 28%.
EXAMPLE 1
Composition of aqeuous bath Cobalt Chloride 20-400 g./l. Stannous
Chloride 10-100 g./l. Ammonium Bifluoride 20-400 g./l. Hydrochloric
Acid (37%) 40-150 mls./l. Ammonium Hydroxide (28%) 10-50 mls./l.
Zinc Chloride 15-175 g./l. Plating Conditions: Temperature of bath
60-80.degree. C. Current density 10-30 A/ft..sup.2 pH of bath
1-3
EXAMPLE 2
Composition of aqueous bath Cobalt Chloride 20-400 g./l. Stannous
Chloride 10-100 g./l. Ammonium Bifluoride 20-400 g./l. Hydrochloric
Acid (37%) 40-150 mls./l. Ammonium Hydroxide (28%) 10-50 mls./1.
Indium Chloride 5-35 g./l. Plating Conditions: Temperature
60-80.degree. C. Current density 10-30 A/ft..sup.2 pH of bath
1-3
EXAMPLE 3
Composition of aqueous bath Cobalt Chloride 20-400 g./l. Stannous
Chloride 10-100 g./l. Ammonium Bifluoride 20-400 g./l. Hydrochloric
Acid (37%) 40-150 mls./l. Ammonium Hydroxide (28%) 10-50 mls./l.
Chromium Chloride 5-55 g./l. Plating Conditions: Temperature
60-80.degree. C. Current density 10-30 A/ft..sup. 2 pH of bath
1-3
EXAMPLE 4
Composition of aqueous bath Cobalt Chloride 100-300 g./l. Stannous
Fluoborate (50%) 25.75 mls./l. Fluoboric Acid 75-225 g./l. Ammonium
Hydroxide (28%) 25-150 m/s./l. Zinc Chloride 10-135 g./l. Plating
Conditions: Temperature 50-85.degree. C. Current density 5-45
A/ft..sup.2 pH 1-3
EXAMPLE 5
Composition of aqueous bath Cobalt Chloride 100-300 g./l. Stannous
Fluoborate (50%) 25-75 mls./l. Fluoboric Acid 75-225 g./l. Ammonium
Hydroxide (28%) 25-150 mls./l. Chromium Chloride 10-75 g./l.
Plating Conditions: Temperature 50-85.degree. C. Current density
5.45 A/ft..sup.2 pH 1-3
EXAMPLE 6
Composition of aqueous bath Cobalt Chloride 100-300 g./l. Stannous
Fluoborate (50%) 25-75 mls./l. Fluoboric Acid 75-225 g./l. Ammonium
Hydroxide (28%) 25-150 mls./l. Indium Chloride 5-35 g./l. Plating
Conditions: Temperature 50-85.degree. C. Current density 5-45
A/ft..sup.2 pH 1-3
* * * * *