Improvements relating to the Coating of Articles with a New Metallic Alloy by Electro-deposition.
Year: 1891

page_text: Date of Application, 8th Aug., 1891
Complete Specification Left, 2nd Nov., 1891-Accepted, 16th Apr., 1892
PROVISIONAL SPECIFICATION.
Improvements relating to the Coating of Articles with a New
Metallic Alloy by Electro-deposition.
We, THE LONDON METALLURGICAL COMPANY LIMITED, and SHERARD
OSBORN COWPER-COLES, Engineer, both of 80 Turnmill Street, in the City of
London, do hereby declare the nature of this invention to be as follows:-
The object of our invention is to produce upon various articles of metal or other
suitable material, a brilliant silvery coating or plating which is better adapted than
silver to resist the tarnishing influences of the atmosphere.
For this purpose we deposit upon the said articles by electrolysis an alloy of
zinc and silver. We find that to protect the silver from the tarnishing effects of
the atmosphere, about from twenty-five to thirty-five per cent. of zinc is sufficient.
When, however, we desire to produce less costly coatings, we employ say from
forty per cent. to ninety per cent. of zinc.
Our said invention, moreover, comprises a method or process of electro-depositing
the alloy whereby we are enabled to obtain a homogeneous coating, that is to say, a
coating in which there is a perfect intermixture of the metals constituting the
alloy, instead of a mere deposit of layers of different composition.
:-
In carrying on our improved method of electro-deposition, we proceed as follows,
ic. We prepare the electrolytic bath by dissolving a suitable quantity of
cyanide of zinc in a solution of cyanide of potassium so as to form a double salt,
with a small excess of the cyanide of potassium. This solution, with the addition
of a small quantity of the double salt of cyanide of potassium and silver, forms the
electrolyte, which is introduced into any suitable electro-plating or electro-typing
apparatus. We employ an anode composed of an alloy of zinc and silver in the
same, or approximately the same proportions as are desired in the alloy to be
deposited; for example for the deposition of an alloy composed of equal parts by
weight of silver and zinc, we use an anode composed of equal or about equal parts
of silver and zinc.
After the cathodes, that is to say, the articles upon which it is desired to form
the deposit, have been placed in the electrolytic bath and the current caused to
How for a short time, the zinc and silver are deposited as an alloy of the desired
composition.
The electrolytic bath may be used either hot or cold, and we can increase or
diminish the hardness of the deposit by varying the proportions of zinc and silver
in the alloy.
An alloy of zinc and silver in, or about in the proportions above stated will
produce a beautiful silvery white coating having all the appearance of silver
and possessing greater powers of resisting the tarnishing influences of the
atmosphere.
We wish it understood that we do not limit ourselves to any special proportions
of silver and zinc, as such proportions may be varied according to the purpose
for which the alloy is required, without departing from the nature of our
invention.
T: 041 1 of 1001

page_text: COMPLETE SPECIFICATION.
Improvements relating to the Coating of Articles with a New
Metallic Alloy by Electro-deposition.
THE LONDON METALLURGICAL COMPANY, LIMITED, and SHERARD OSBORN
COWPER-COLES, Engineer, both of 80 Turnmill Street, in the City of London,
do hereby declare the nature of this invention and in what manner the same is to
be performed to be particularly described and ascertained in and by the following
statement:-
This invention relates to the coating by electro-deposition of articles of metal or
other suitable material with a new metallic alloy, and its object is to produce upon
the said articles a brilliant coating or plating resembling silver but which is better
adapted than silver to resist the tarnishing influences of the atmosphere.
For this purpose we deposit upon the said articles by electrolysis an alloy of
zinc and silver. We find that to protect the silver from being rapidly tarnished
by the atmosphere, about from thirty-five to twenty-five per cent. or even less zinc
is sufficient. When however we desire to produce less costly coatings, we employ
say from forty per cent, to ninety per cent. of zinc.
Our said invention moreover comprises a method or process of electro-depositing
the aforesaid alloy, whereby we are enabled to obtain a homogeneous coating, that
is to say, a coating which consists throughout of a perfect intermixture of the
metals constituting the alloy, instead of a succession of layers having a different
composition.
In carrying on our improved method of electro-deposition, we proceed as follows,
that is to say; we prepare an electrolytic bath by dissolving a suitable quantity of
cyanide of zinc in a solution of cyanide of potassium so as to form a double salt,
having a slight excess of the cyanide of potassium. To this solution we add a
small quantity of the double salt of the cyanides of potassium and silver, the two
together forming the electrolyte or electrolytic bath which is introduced into any
suitable electro-plating or electro-typing apparatus. We employ an anode
composed of an alloy of zinc and silver in the same, or approximately the same,
proportions as are desired in the alloy to be deposited for example, for the
deposition of an alloy composed of equal parts by weight of silver and zinc, we use
an anode composed of equal or about equal parts of the said metals.
After the cathodes, that is to say, the articles upon which it is desired to form the
deposit, have been placed in the electrolytic bath, and the current caused to flow,
the zinc and silver are deposited thereon as an alloy of the desired composition.
The electrolytic bath may be used either hot or cold, and we can increase or
diminish the hardness of the deposit by varying the proportions of zinc and silver
in the alloy.
We wish it understood that we do not limit ourselves to any special proportions
of silver and zinc, as such proportions may be varied according to the purpose for
which the alloy is required, without departing from the nature of our invention.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed we declare that what
we claim is :-
:-
First. The method of depositing by electrolysis, an alloy of silver and zinc on
metal and other suitable articles, substantially as herein described.
Second. An article of metal or other suitable material that has been coated with
an alloy of silver and zinc by electro deposition, for the purpose specified.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicants.