ELECTROPLATED BLANK FOR COINS, MEDALLIONS AND TOKENS

FLAN ELECTROPLAQUE POUR MONNAIE, MEDAILLON ET JETON

English Abstract

An electroplated blank capable of having insignia
minted on at least one face to form coins, medallions or
tokens, the blank having opposed faces and a peripheral
side edge and an electroplated coating comprising 0.5 to
4% by weight tin, the balance copper, completely
enveloping said blank. The coating forms a thickness of
from about 5 µm to about 50 µm on at least said face to
be minted.

French Abstract

Flan plaqué par galvanoplastie sur lequel on peut frapper des insignes au moins sur l'une des faces pour former des pièces de monnaie, des médaillons ou des jetons, le flan ayant des faces opposées et une tranche et un placage comprenant de 0,5 à 4 % en poids d'étain et le reste en cuivre enveloppant complètement ledit flan. Le placage a une épaisseur comprise entre environ 5 µm et environ 50 µm sur au moins ladite face à frapper.

Claims

- 12 -
The embodiments of the invention in which an
exclusive property or privilege is claimed, are defined as
follows:
1. A corrosion and wear resistant electroplated blank
having a copper lustre and appearance capable of having
insignia minted on at least one face, comprising:
a core blank of a first metallic material, said
core blank having opposed faces and a peripheral side edge,
at least one of said faces being impressionable by a mint
die, and
an electroplated coating of a second metallic
material completely encasing said core blank and providing
a surface thickness on at least said impressionable face of
from about 5 ~m to about 50 ~m, said second metallic
material having a tin content of from about 0.5% to about
4.0%, by weight, with the balance being copper.
2. A blank as claimed in claim 1, in which said first
metallic material is at least one selected from the group
consisting of iron, low carbon steel, stainless steel,
nickel, nickel-plated steel, zinc and zinc alloys, copper
and copper alloys, magnesium and magnesium alloys, and
pretreated aluminum and aluminum alloys.
3. A blank as claimed in claim 2, in which said second
metallic material has a tin content of about 2% by weight,
the balance being copper.
4. A corrosion and wear resistant electroplated coin
having a copper lustre and appearance and insignia minted
on at least one face, comprising:
a coin core blank having opposed faces and a
peripheral side edge of a first metallic material which is
soft enough to be deformed by coin dies during minting, and
an electroplated coating of a second metallic material
completely encasing said blank, which contains from about
0.5 to about 4% tin by weight, with the balance copper, and

-13-
having a face thickness of from about 5~m to about 50~m,
said insignia being formed by minting after the coating is
electroplated.
5. A coin as claimed in claim 4, in which the first
and the second metallic materials are metallurgically
bonded by interdiffusion due to heat treatment.
6. A coin as claimed in claim 5, in which the first
metallic material is at least one selected from the group
consisting of iron, low carbon steel, stainless steel,
nickel, nickel-plated steel, zinc and zinc alloys, copper
and copper alloys, magnesium and magnesium alloys, and
pretreated aluminum and aluminum alloys.
7. A coin as claimed in claim 5, in which the first
metallic material comprises iron, low carbon steel or
stainless steel.
8. A coin as claimed in claim 5, in which the first
metallic material comprises nickel or nickel-plated steel.
9. A coin as claimed in claim 5, in which the first
metallic material comprises zinc or zinc alloy.
10. A coin as claimed in claim 5, in which the first
metallic material comprises copper or copper alloy.
11. A coin as claimed in claim 5, in which the first
metallic material comprises magnesium or magnesium alloy.
12. A coin as claimed in claim 5, in which the first
metallic material comprises aluminum or aluminum alloy.
13. A coin as claimed in claim 5, in which the first
metallic material is low carbon steel and the second
metallic material comprises about 2% tin by weight, the
balance copper.
14. A corrosion and wear resistant electroplated coin
having a copper lustre and appearance, capable of having an
insignia minted on at least one face, comprising:
providing a core blank of a first metallic material
and of a prescribed size, with opposed faces and a

- 14 -
peripheral side edge, at least one of said faces being
impressionable by a mint die, and an electroplated coating
of a copper alloy completely encasing said core blank to
provide a surface thickness on at least said impressionable
face of from about 5~m to about 50~m, said copper alloy
having a tin content of from about 0.5% to about 4% by
weight, with the balance being copper, said insignia being
minted on at least said impressionable face.
15. A coin as claimed in claim 14, in which said copper
alloy coating and said core blank material are
metallurgically bonded by interdiffusion due to heat
treatment.
16. A process for producing a corrosion and wear
resistant blank having a copper lustre and appearance
capable of having an insignia minted on at least one face,
comprising:
providing a core blank of a first metallic material
and of a prescribed size, with opposed faces and a
peripheral side edge, at least one of said faces being
immpressionable by a mint die, and
electroplating said core blank with a second
metallic material to completely encase said core, blank to
provide a surface thickness of from about 5~m to about
50~m on at least said impressionable face, said second
metallic material having a tin content of from about 0.5%
to 4.0% by weight, with the balance being copper and
incidental impurities.
17. A process as claimed in claim 16, in which said
core blank is subjected to a dilute acid rinse prior to
electroplating.
18. A process as claimed in claim 16, in which the core
blank is annealed prior to electroplating.
19. A process as claimed in claim 16, in which said
core blank is annealed after electroplating to provide a
metallurgical bond between the electrodeposited coating and
the core material.

- 15 -
20. A process as claimed in claim 19 wherein said
annealing is carried out in a reducing atmosphere for up to
about 15 minutes at about 700°C.
21. A process for producing a corrosion and wear
resistant electroplated coin having a copper lustre and
appearance and a mint deformed insignia on at least one
face, comprising:
providing a coin core blank of the desired size and
shape having opposed faces and a peripheral side edge of a
first metallic material which is soft enough to be readily
deformed by coin dies during minting;
electroplating said coin blank with a coating of a
second metallic material to completely encase said coin
core blank with a coating having a face thickness of about
m to about 50 m, said second metallic material
comprising about 0.5 to about 4% tin by weight, with the
balance copper, and forming insignia on said at least one
face of the plated blank by at least one coin die deforming
the surface thereof.
22. The process of claim 21, including the step of
softening the coin blank by annealing prior to
electroplating.
23. The process of claim 22, including the step of
softening the coin blank by annealing after plating and
prior to forming the insignia thereon.
24. The process of claims 19, 20 or 23 in which the
coin blank is annealed in the presence of hydrogen gas.
25. A process according to claims 16, 17, 18, 19, 20,
21, 22 or 23 in which said first metallic material is at
least one selected from the group consisting of iron, low
carbon steel, stainless steel, nickel, nickel-plated steel,
zinc and zinc alloys, copper and copper alloys, magnesium
and magnesium alloys, and pretreated aluminum and aluminum
alloys.
26. A process as claimed in claim 25, in which said
second metallic material has a tin content of about 2% by

- 16 -
weight, the balance copper.
27. A process according to claim 16, 17, 18, 19 or 20
including minting an insignia on said coated impressionable
face.

Description

~013639
RA~ Ouhv OF TNE ~ ON
This invention relates to metal alloy coins,
medallions or tokens and to blanks used for the
production of coins, medallions or tokens. More
particularly, this invention relates to said coins,
blanks and medallions and to blanks for the production
thereof having improved wear resistance compared to
copper alloy or copper plated or clad coins while
maintaining a cupric luster and appearance.
In recent years, the rising cost of coinage metals
has encouraged many countries to strike relatively
~n~Yr~ncive alloy coins in an effort to obtain reduced
production costs. Various alloys of copper and zinc as
well as nickel, aluminum and other metals have been used
with varying success.
The integrity of the coins is frequently judged by
the general public by their appearance which is expected
to be of a luiter or colour of gold, silver or copper,
depen~in~ on their face value. It is desirable that the
coins do not change colour with age or otherwise corrode.
In addition to avoiding these undesirable features, any
new coin should also be of an acceptable weight and may
require certain electrical and magnetic properties to
permit them to be acceptable for use in vending machines.

~3639
Other materials requirements for coins are that
~hey must not be easy to counterfeit, should provide
specific properties for coin selection devices, must be
capable of taking a good minting impression while having
a sufficient surface hardness after minting to avoid
undue wear, and should be inexpensive.
Canadian Patent No. 1,219,708 issued March 31, 1987
and U.S. Patent No. 4,579,761 issued April 1, 1986
disclose a process for producing an aureate coin and coin
blank having an electroplated coating cont~i ni ng about 8
to 16%, preferably about 11 to 14%, by weight tin, the
balance copper. The coating thickness on the core faces
is about 10 to 150 ~m, preferably about 30 to 50 ~m. The
coins and blanks have a golden appearance and are
suitable for replacement of gold coins.
Because of the high cost of the refined copper,
coinaqe bronze, defined as an alloy group containing
greater than 95% copper, with 1 to 4% zinc and 0 to 1
tin and having a characteristic copper red colour, or
other copper alloy coins currently in use, are expensive.
The seigniorage, which is the difference between the
face value of the coin and its production cost,
accordingly becomes small or of deficit value. The use
of pure copper plating on steel or zinc cores has been
found to produce coins subject to corrosion or wear
problems. This was believed to be due to the coarse
grain size, deposit porosity and the inherent poor wear
resistance of such copp~r.

It is therefore an object of this invention to
provide a coin with satisfactory corrosion and wear
resistance which is relatively inexpensive to produce and
has a copper lustre and appearance suitable for
replacement of coins of coinage bronze alloy which are
relatively expensive.
It is an object of another aspect of the invention
to provide a copper alloy coin having suitable
characteristics for use in coin operated vending
machines.
SU~MA~Y OF T~E lNvk..~lON
In accordance with the present invention, a low
tin bronze alloy, bonded to a core blank, has a finer
grained den~er deposit than copper coatings and thus
provides better corrosion resistance. The tin-copper
alloy provided is believed to provide better protection
than pure copper to a core such as a ~teel substrate due
to a weaker galvanic corrosion couple between the metals,
and due to a more dense electrodeposit.
The addition of tin in the range of 0.5 to 8%
greatly increases the resistance of the alloy coating to
wear when used as a circulating coin.
The foregoing and other objects of the invention
are obtained by means of an electroplated blank capable
of having an insignia minted on at least one face,
comprising: a core blank o~ a first metallic

20~3639
material, said core blank having opposed faces and a
peripheral side edge, at least one of said faces being
impressionable by a mint die, and an electroplated
coating of a second metallic material completely
encasing said core blank and providing a surface
thickness on at least said impressionable face of from
about 5 ~m to about 50 ~m, said second metallic material
having a tin content of from about 0.5% up to a~out 8.0%
by weight, preferably about 2~ to 8%, with the balance
being copper and incidental impurities.
Such objects are produced by ~eans of a process
comprising: providing a core blank of a first metallic
material and of a prescribed size, with opposed face and
a peripheral side edge, at least one of said faces being
impressionable by a mint die, and electroplating said
core blank with a second metallic material to completely
encase said blank and thereby provide a surface thickness
of from about 5 ~m to about 50 ~m on at least said
impressionable face, said second metallic material having
a tin content of from about 0.5% up to about 8.0% by
weight, preferably about 2% to 8%, with the balance being
copper and incidental impurities.
BRIEF D~SCRIPTION OF THE DRAWING
The process of the invention and the products
produced thereby will now be described with reference to
the following examples and the accompanying drawings, in
which:
Figure 1 is a cross-section showing the
microstructure of annealed copper bonded steel (C-B-S)
and of bronze bonded steel (B-B-S) produced according to
the process of the invention; and
Figure 2 is a graph showing thickness loss as a
result of wear over time.

2~:~ 3:~39
DESCRIPTION OF ln~ ~h~r~KK~ EMBODINENT
Although the prece~i ng description and the
following examples make reference to coin blanks, it will
be understood that the term "coin" u~ed herein in the
specification and claims is intended to include coins,
medallions and tokens and blanks therefor. Also,
although the metallic material of ~he core blank is
exemplified in the following examples as low carbon
steel, it will be understood that the ~etallic core
material may for example comprise iron, low carbon steel,
stainless steel, nickel, nickel-plated steel, zinc, or
alloys of zinc, copper or various alloys of copper
containing zinc and/or nickel and/or tin, magnesium and
magnesium alloys, and aluminum or aluminum alloys
suitably pretreated.
The core blank must be soft enough to be deformed
by coin dies dùring minting and the core may be
advantageously annealed before or after plating to give
the blank with the electroplated coating a satisfactory
low hardness for minting. Annealing after electroplating
is also advantageous in that it can be used to create a
metallurgical bond by interdiffusion between the
electroplated low tin copper coating and the c~re
material. If the core material is already soft enough
for minting, as with zinc, annealing may be omitted.
The said core may be burnished before or after
annealing, to give the blan~ with the electroplated
coating a satisfactory luster.

~ 3~39
E:Xa~LE 1
A batch of rimmed coinage blanks made of low
carbon steel and weighing 949 grams was loaded into a
perforated, rotatable, horizontal plating barrel having a
length of 15 cm and a diameter of 10 cm. The barrel was
first passe~ through a cleAning cycle consisting of
sequential washes in a 10% detergent solution, cold
water, 10% hydrochloric acid, and a second cold water
wash. The blanks contained in the plating barrel were
then immersed in an alkaline cyanide bronze plating bath
containing copper, tin, potassium hydroxide and
potassium cyanide. A current of 15 amps was applied to
the bath for approximately 1.8 hours while the
temperature of the bath was maintai~e~ between about 55~C
and 60~C.
When removed from the bath, the total mass of
coinage blanks was found to have increased by 58.7 gramS,
equivalent to 5.83% of the total charge weight of the
blanks. A wet analysis of the blanks showed the blanks
to have a deposit containing 2.12% tin by weight.
After plating, the coinage blanks were Annealed in
a reducing atmosphere at 700 C for 15 minutes in the
presence of hydrogen. The coinage blanks were found to
have an electrodeposit thickness of bronze on their faces
of approximately 21 ~m, and around their rims of
approximately 30 ~m.

2~3~3~
Such coatings were found to be metallurgically
bonded to the steel blanks, and had a finer grain deposit
than pure copper similarly bonded and annealed, as shown
by the microstructures in Figure 1 for bronze bonded
steel (B-B-S) and copper bonded steel (C-B-S)
respectively.
Bronze bonded steel coinage blanks prepared
according to the process of the present invention were
evaluated with copper bonded steel blanks and Canadian
one cent coin blanks for corrosion resistance and for
wear resistance.

2~)~363~
.
The parameters of the coinage test sample8 are shown ~n
Table 1.
. Table 1
D2posit
Diameter Thic~necs W~ight Thk Wt Co~p'n
Sample (mm) (mm)(g) ~m % %
C-B-S 18.S6 0.982.22 Face:21
5.78~00 Cu
Edge:30
B-B-S 18.57 0.982.22 Face:21
5.832.1 Sn
Edge:31 97.9 Cu
Cdn. 1~ 19.05 1.382.50 N/A N/A1 5 Zn
98.0 ~u.
EXAMPLE 2
In the corrosion test, coins or blanks were immersed
in a 2% NaCl solution for 4 hours. The results o~ a
co~,osion test co~lcted on 10 samples of each blank type
are shown in Table 2.
Table 2
Sample On Faces on Edqe
C-B-S 11 rust spots/l~ blanks 7 rust spots/10 blan~s
B-8-S 0/10 blanks 0~10 blanks
0/10 coins 0/10 coins
Canadian l¢

~36~9
Black rust spots were found only on the copper
bonded steel samples. All rust spots were smaller than 1
mm in size.
EXAMPLE 3
A rotating drum wear test was carried out on 16
samples of each blank type. In this test, samples were
tumbled in a rotating cylinder having a cloth lining
backed by rubber, a hump on the circumference to tumble
the pieces each revolution, and a lo~d; n~ hole on one
side. At the start, pieces were weighed, dipped in
synthetic sweat solution, sealed into the cylinder and
rotated, with the test cycle being repeated at 100 hour
intervals. The cumulative average surface thickness loss
for the samples as a function of test duration up to 300
hours is shown in Figure 2. The bronze bonded steel
samples showed better wear resistance than the copper
bonded steel blanks and Canadian one cent samples, while
the latter two sample types had similar wear resistance
over the 300 hour test period.
In general, the bronze bonded steel blanks were
superior to the copper bonded steel blanks in both
corrosion and wear tests.
The steel core blanks were sufficiently soft to
take a clear impression from a mint die without causing
undue wear on such dies. The electrodeposited alloy
coating exhibited sufficient surface hardness that the
insignia minted thereon was not worn away after prolonged
wear testing.

201~639
While this invention is particularly suitable for
producing coins to be used as legal tender, it will be
understood that it is beneficial in the production of
medallions, tokens and metallic tags as well. Other
embodiments of the invention will be readily apparent to
a person skilled in the art, the scope of the invention
being defined by the appended claims.