Improvements in and connected with the Electrodeposition of Copper and other Metals on Rotary Cathodes.
Year: 1898

page_text: Date of Application, 22nd June, 1898-Accepted, 22nd Oct., 1898
[Communicated from abroad by EMILIEN DUMOULIN, of 23, Boulevard de
Strasbourg, Paris, in the French Republic, Gentleman.]
Improvements in and connected with the Electrodeposition of
Copper and other Metals on Rotary Cathodes.
I, WILLIAM EDWIN HEYS, of 70, Market Street, Manchester, in the County
of Lancaster, Chartered Patent Agent, do hereby declare the nature of this in-
vention, and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement:-
In the Specifications of Letters Patent No. 16360 dated the 31st day of August
1895 and 2709 dated the 2nd day of February 1897, relating to the electro-
deposition of copper and other metals, there are described certain organic mem-
branes and materials which are arranged in contact with rotary cathodes upon
which the metal is deposited, for the purpose of ensuring a smooth uniform and
homogeneous product.
These organic membranes and materials which have been, and are hereinafter,
called "impregnators," act by momentarily covering or coating and electrically
or mechanically insulating temporary asperities or prominencies on the deposit
and thus prevent or retard deposition of the metal thereon. Meanwhile, the mole-
cules of metal are normally deposited around the asperities or prominencies and
these latter thus become level with the general surface of the cathode. The coat-
ing or covering derived from the impregnators is gradually removed by the
motion of the cathode in the electrolyte and in contact with the impregnators.
By this use of the impregnators my foreign correspondent not only obtains
deposits having remarkably excellent physical and mechanical qualities but he
also obtains them much more rapidly. For example, a homogeneous sheet of
copper about one twenty-fifth of an inch thick may be obtained in about tem
hours working. This rapidity of deposit is an economical advantage, but it has
also the disadvantage that, owing to the high density of the current employed, a
rapid heating of the electrolytic bath ensues and the increase of temperature
therein may easily suffice to bring about the softening or solution of some of
the albuminous or gelatinous constituents of the impregnators. These con-
stituents commence to soften when the electrolytic bath reaches a temperature
of about 86° F. (or about 30° C.), and even begin to disintegrate and dissolve in
the bath. Under such a condition of temperature, the controlling action of the
impregnators is completely changed and instead of temporarily coating or cover-
ing slightly the asperities and prominencies, parts of them may permanently
adhere to, and little by little, become imprisoned in the metallic deposit. When
the metal is subsequently annealed, this imprisoned matter, by its combustion,
produces gases under pressure which render the metal porous and short.
In order to obviate this defect and inconvenience, my foreign correspondent
treats the impregnators with a solution of formic aldehyde.
In carrying out the treatment the impregnators are thoroughly impregnated
with the solution of formic aldehyde, after which they are copiously washed in

page_text: water to remove the formic aldehyde, or this substance is neutralised or decom-
posed as for example by means of acetic acid. The object of the washing
neutralisation or decomposition is that the action of the aldehyde may not be
continued further than is necessary, and further to prevent its admission to the
electrolytic bath. The solution may be used in various strengths, but is generally
employed within the limits of ten per cent. and forty per cent. according to the
nature of the material of which the impregnators are composed, to the time within
which the insolubilisation must be effected and other minor conditions, such as
temperature. For example, if a forty per cent. solution of formic aldehyde be
used, the impregnators, if of the nature of parchment, may be soaked therein for
one and a half hours, be removed from the solution and dried, and then soaked
in clean water for fifteen hours or until wanted. Soaking for a longer time is
not prejudicial. Again, if similar impregnators are treated with a ten per cent.
solution of formic aldehyde, they may be suffered to remain therein for twenty-
four hours and be thereafter treated as described for the forty per cent. solution.
If time cannot be spared for the soaking in water, the impregnators, after removal
from the formic aldehyde solution may be heated in a bath of commercial acetic
acid and be thereafter thoroughly washed in clean water. It will be understood,
as herein before described, that the strength of the formic aldehyde solution and
the duration of the period of the immersion of the impregnators therein may be
varied within comparatively wide limits according to the conditions in each case.
In like manner, the subsequent treatment may also be varied.
When the impregnators, rendered more or less insoluble as hereinbefore
described, are employed in connection with rotary cathodes in the electrodeposition
of copper and other metals, the metal may be deposited with equal facility in a
hot or in a cold bath, and the impregnators are found to be much more durable.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, as communicated to
me by my foreign correspondent, I declare that what I claim is :-
1. In the process for the deposition of copper and other metals by electro-
lysis upon rotary cathodes, the use of impregnators which have been rendered
more or less insoluble, substantially as and for the purpose herein before described.
2. Impregnators of the type hereinbefore set forth for use in the electrodeposi-
tion of copper and other metals on rotary cathodes, which impregnators have been
rendered more or less insoluble, substantially as and for the purpose hereinbefore
described.