AN IMPROVED SYSTEM OR MODE OF COATING IRON WITH COPPER
Year: 1855

page_text: LETTERS PATENT to John Henry Johnson, of 47, Lincoln's Inn Fields, in
the County of Middlesex, and of Glasgow, North Britain, Gentleman, for
the Invention of "AN IMPROVED SYSTEM OR MODE OF COATING IRON WITH
COPPER." A communication.
PROVISIONAL SPECIFICATION left by the said John Henry Johnson at
the Office of the Commissioners of Patents, with his Petition, on the
3rd January 1855.
I, JOHN HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County of
Middlesex, and of Glasgow, North Britain, Gentleman, do hereby declare the
nature of the said Invention for "AN IMPROVED SYSTEM OR MODE OF COATING
IRON WITH COPPER," a communication from abroad, to be as follows:-
This Invention relates to the chemical or galvanic coating of iron with
copper, and consists, first, in the application of the sulphate of copper for the
galvanic coating of iron which has been previously covered by a thin pre-
servative coating, for the purpose of preventing the sulphuric acid of the
sulphate from acting upon the iron.
Second, in the application of a thin preservative coating on the iron which
is to be coated with copper by the aid of the sulphate of copper.

page_text: Third, in the application of lead as a preservative coating, as a substitute
for copper.
Fourth, in the application to this operation of baths of copper and lead.
And, fifth, of a process for cleaning the metal surfaces.
ल
The first bath employed in the process of coppering consists of a solution of
cyanate of potassium and cyanate of copper, in water sufficient to produce
complete saturation. This bath is used to give a slight preservative coat of
copper to the iron surfaces. The sulphate of copper bath consists of a heated
solution of sulphate of copper, slightly diluted with water, to which is after-
wards added a certain amount of-sulphuric acid; when the-bath is complete.
The articles taken out of the first bath, which are covered with a slight
coating of copper, are washed in water and plunged into the second bath, but
not before the electric battery of this bath has been brought into action. The
articles are left in this bath for some hours, at the expiration of which time
they are covered with a thick coating of copper, which adheres firmly thereto.
In some cases it is proposed to substitute for the first preservative layer or
coating of copper a coating of lead, which is much more advantageous.. This
last-mentioned bath is composed of oxide of lead (litharge). dissolved in watér,
which holds.in sölution.ten per cent. of potash. Fór effecting the cleaning or
preparation of the metal plates before entering the. baths, they are submitted
to the action of dilute sulphuric acid, and washed with water; they are.then
immersed for a few moments in boiling water. The are next plunged into a
lye of caustic soda, and are finally submitted to the action of lime, in which
substance they are allowed to remain for several weeks, thereby producing a
metallic surface, chemically pure; that is, totally void of any foreign matter
whatever.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Johu Henry Johnson in the Great Seal, Patent Office on the
3rd July 1855...i
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County of Middlesex,
and of Glasgow, North Britain, Gentleman, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Third day of January, in the year of our Lord One
thousand eight hundred and fifty-five, in the eighteenth year of Her reign, 'did,
for Herself, Her heirs and successors, give and grant unto. me, the said John

page_text: Henry Johnson; Her special license that I, the said John Henry Johnson, my
executors, administrators, and assigns, or such others as I, the said John Henry
Johnson, my.executors, administrators, or assigns, should at any time agree
with, and no others, from time to time and at all times, thereafter during the
term therein expressed, should and lawfully might make, use, exercise, and
vend, within the United Kingdom of Great Britain and Ireland, the Channel
Islands, and Isle of Man, an Invention for "AN IMPROVED SYSTEM OR MODE
OF COATING IRON WITH COPPER," being a communication from abroad, upon
the condition (amongst others) that I, the said John Henry Johnson, by a
instrument in writing under my hand and seal, should particularly describe
and ascertain the nature of the said Invention, and in what manner the
same was to be performed, and cause the same to be filed in the Great
Seal Patent Office within six calendar months next and immediately after
the date of the said Letters Patent.
an
NOW KNOW YE, that I, the said John Henry Johnson, do hereby declare
the nature of the said' Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement, that is to say :-
The said Invention relates to the coating of iron with copper by means of
a chemical or galvanic process, and to processes preliminary thereto..
In order that iron may be brought into a suitable condition for the recep-
tion of a permanent coating of copper, it is proposed, first, to deposit a thin
preservative covering of copper
on the iron by any of the ordinary processes,
& then to finish the process by means of a solution of sulphate of copper.
It is well known that iron is not only usually covered with a coat of oxide,
but that there is upon its surface a more or less thick layer of scale, consisting
of a carburrett of iron. Now, in order that the copper may adhere effectually
to the surface of the iron, its surface must be thoroughly cleansed from all
extraneous matter having a tendency to destroy the chemical purity of the
copper. To effect this, the iron is submitted to the action of dilute sulphuric
acid until the layer or crust is removed from its surface; it is then washed
first in cold water, and then in boiling water, for a few seconds. To remove
the last traces of the acid, the iron must be placed in a lye of caustic soda;
and, finally, the iron must be placed in quick lime, and kept there for several
weeks, at the end of which time it will have acquired a surface chemically
pure, that is to say, one on which there is no extraneous matter whatever.
The iron, having been thus prepared, must be plunged into the first bath,
by which means a thin coat of copper is deposited upon the metal, and the
iron is thereby protected against the action of the acid in the second bath;
5.

page_text: this latter bath consisting of sulphate of copper, rendered strongly acid by the
addition of sulphuric acid.
The following is the manner in which the first bath is prepared :-Dissolve in
every imperial pint of water from 350 to 400 grains (troy weight) of cyanide
of potassium, and add cyanide of copper, until the solution is completely
saturated.
The iron to be coppered must be placed in this bath for about an hour, &
submitted to the action of a galvanic battery, composed of many pairs of
plates, which may be comparatively small in size, experience shewing that in
this case the number of plates is a more important consideration than their area
or size. It has also been found that, whatever may be the number or size of
the pieces of iron placed in the bath, the coating of copper will not properly
adhere to their surfaces unless hydrogen be disengaged. A battery of from
24 to 30 pairs of plates, of which the zinc plates are about two inches in
breadth by 6 inches in height, will produce the requisite discharge of hydrogen
when iron articles with a surface of several square yards are immersed in
the bath.
The second bath is prepared in the following manner:-A hot solution of
sulphate of copper, of a strength when cool of 24° of Baume's areometer, is
first made; as much water is then added as will bring down the strength of
the solution to 20°; a sufficient quantity of sulphuric acid is then added
to raise it again to 22°. The iron having been removed from the first bath
covered with a thin coating of copper, is washed in water and plunged into
the second bath, but not before the battery has been put into action. In
arranging the articles in this bath, care must be taken that they be not sub-
mitted to the action of the second bath, until the galvanic action of the battery
has been tested. When exciting a proper amount of action, a sufficient
quantity of copper will be then deposited in a very short time. The object of
this precaution is to complete the work of the first bath, in case of any inter-
stices or fissures being left in the covering or preservative coating which has
been deposited upon the article. The deposition of copper is then allowed to
continue for some hours, until the iron is covered by a coating of copper so
thick & adherent that no chemical agent can attack the iron without first
acting upon the copper coating.
.
In order to effect this second deposit of copper, the arrangement of the
battery should be changed, & the surface of the plates should be brought
into as close relation as possible with the articles to be coated with copper.
The processes herein- before described for preparing the iron for the action of
the second bath will be found effective if they have been carefully performed;

page_text: but over & above the necessity which will be found of employing .a.compara-
tive powerful current of electricity, great care must be taken in the manage-
ment of some articles. .If unskilfully dealt with, dark spots will appear upon
their surfaces when in the second.bath, and these spots are certain indications
of the porosity of the preservative covering or coating, and the article will
then require to be re-cleaned, and the whole of the work gone over again.
Another part of this Invention relates to the obviating of this inconvenience.
I propose to substitute for the preservative covering of copper a coating-of
lead, which advantageously answers the same purpose, and is less liable than
the copper to combine with the acid in the sulphate of copper bath. The
reduction by galvanism of the lead contained in the oxide of lead dissolved in
potass requires only a small expenditure of electricity. It is possible also to
obtain a coating of any desired thickness, although, as the lead is soft, I must
avoid increasing its thickness beyond a certain point, for fear of diminishing
the solidity of the last coating of copper. Layers or coats galvanically
deposited, by increasing in thickness, increase at the same time in extent
and finish, by gradually filling up the pores and interstices in the surface.
Another advantage derived from the lead bath is, that it is cheaper than the
alkaline copper baths, and produces a better result.
The following is the mode of preparing the lead bath:-Dissolve oxide of
lead (litharge) in water, holding in solution ten per cent. of potash until satura-
tion, and maintain the point of saturation by placing in the bath more of the
oxide, in proportion to the extent or size of the articles to be submitted to
the action of the bath. This bath presents two other great advantages over
the alkaline copper bath; first, it is not, as is the case with the cyanide of
potassium, susceptible of decomposition into carbonate of potash under the
influence of a moist atmosphere; second, it gives rise to no deleterious emana-
tions injurious to the health of the workman.
Having now described and particularly ascertained the nature of the said
Invention, and the manner in which the same is or may be used or carried into
effect, I would observe, in conclusion, that I do not confine or restrict myself
to the precise details or arrangements which I have had occasion to describe
or refer to, as many variations may be made therefrom without deviating from
the principles or main features of the said Invention; but what I consider to
be novel and original, and therefore claim as the Invention secured to me by
the herein-before in part recited Letters Patent, is,-
First, the system or mode of cleaning and preparing the iron to be sub-
sequently coated, as herein-before described.
Second, the application of a thin preservative covering or coating of copper

page_text: to the iron, which is to be. subsequently thickly coated by the aid of sulphate
of copper.
Third, the application and use of sulphate of copper for the last or perma-
nent coating of iron with copper, such iron having been first covered by a thin
preservative coating, to protect it from the action of the sulphuric acid of the
second-bath, as herein-before described.
Fourth, the application and use of lead as a preservative coating in place of
the thin copper preservative coating, as herein-before described.
In witness whereof, I, the said John Henry Johnson, have hereunto
set my hand and seal, this Third day of July, in the year of our Lord
One thousand eight hundred and fifty-five.
J. HENRY JOHNSON. (L.S.)
✓ LONDON
Printed by GEORGE EDWARD EYRE and WILLIAM SPOTTISWOODE,
Printers to the Queen's most Excellent Majesty. 1855.
**