AN IMPROVED METHOD OF PRESERVING COPPER AND OTHER METALS FROM CORROSION OR OXYDATION
Year: 1830

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, GEORGE
GWINNETT BOMPAS, of Fishponds, in the County of Gloucester, Doctor of
Physic, send greeting.
WHEREAS His present most Excellent Majesty King William the Fourth,
by His Letters Patent under the Great Seal of Great Britain, bearing dato at
Westminster, tho Fourth day of November, in the first year of His reign,
did, for Himself, His heirs and successors, give and grant unto me, the said
George Gwinnett Bompas, His especial licence, that I, the said George
Gwinnett Bompas, my exors, adññiors, and assigns, or such others as the
said Georgo Gwinnett Bompass, my exors, adññors or assigns, should at any
time agree with, and no others, from time to time and at all times during the
term of years therein mentioned, should and lawfully might make, use,
exercise, and vend, within England, Wales, and the Town of Berwick-upon-
Tweed, my Invention of "AN IMPROVED METHOD OF PRESERVING COPPER AND
OTHER METALS FROM CORROSION OR OXYDATION;" in which said Letters Patent
there is contained a proviso, obliging me, the said George Gwinnett Bompass,
by an instrument in writing under my hand and seal, particularly to describe
and ascertain the nature of my said Invention, and in what manner the same
is to be performed, and to cause the same to be inrolled in His Majesty's
High Court of Chancery within six calendar months next and immediately
after the date of the said in part recited Letters Patent, as in and by the same,
reference being had, will more fully and at large appear.

page_text: NOW KNOW YE, that in compliance with the said proviso, I, the said
George Gwinnett Bompas, do hereby declare that the nature of my said
Invention, and the manner in which the same is to be performed, is described.
and ascertained as follows (that is to say):-
The said improved method of preserving copper and other metals from
corrosion or oxydation, is by causing the metal intended to be placed and con-
tinued in an electric or galvanic state or action, but which state or action
should be so slight, as only just to neutralise the corrosive action or influence of
the water or other liquid in which the metal to be protected may be immersed
or with which it may be in contact. The electric or galvanic state or action
to protect the metal exposed to corrosion from sea water or water impregnated
with analogous or similar saline matter is to be induced by attaching, in the
manner after described, a piece of alloyed or compound metal, which shall be
positive in the galvanic circle to the metal to be protected, but which shall be
so alloyed or compounded as to be only sufficiently positive to induce the
before mentioned slightly electric or galvanic state or action. For example,
the protecting compound metal or alloy should be so positive in the galvanic
circle to the metal to be protected, that, when immersed together in contact
for an hour more or less in a saline solution containing four ounces of muriate
of soda to each gallon of water at a temperature of about sixty degrees, an
electric tension should be produced of from two hundred to five hundred
degrees measured by a galvanometer, which indicates about seven hundred
and fifty degrees when tested by copper and zinc plates, each of them'
having a surface of thirty-six inches. This alloy may be formed of various
metals or metallic combinations, having respectively the electrical relation
before-mentioned to the metal intended to be protected. Thus, if copper be
to be protected in sea-water, as in the case of copper sheathing on ships, the
alloy or compound metal to be attached to it may be composed of from ninety
to two hundred parts of zinc, combined with one hundred parts of copper. If
the copper to be protected is impure; so as to make it more positive, the pro-
portions of zinc in the protecting alloy or compound metal must be increased
in proportion as it is become more positive; and where the liquid in which
the metal is immersed, instead of being sea water, acts with less energy upon
the metal, or more nearly approaches to pure water; the proportions of zinc or
tin in the protecting alloy or compound metal must be increased. If lead be
to be protected in sea-water, the alloy or compound métal to be attached to it
may consist of from fifty to one hundred and fifty parts of lead' combined with
one part of zinc, or from fifty to one hundred and fifty parts of tin combined

page_text: with one part of zinc. If tin be required to be protected, an alloy may be
employed consisting of from fifty to two hundred parts of tin combined with
one part of zinc. If iron be required to be protected, an alloy of tin may bo
employed, consisting of from ten to one hundred and fifty parts of tin com-
bined with one part of zinc. Any compound metal used for purposes exposed
to the action of sea water may be protected from corrosion in the same
manner, by attaching to the compound metal to be protected another alloy or
compound metal, in which the proportion of that metal, forming part of the
compound metal to be protected which is positive in the galvanic circle, is
considerably increased, so as to cause such an electric tension as before men-
tioned; and in those cases of compound metals, where the metal which is
positive in the galvanic circle is so greatly the principal component part as to
be incapable of such an increase in the protecting alloy or compound metal,
the metal to be protected may be considered as an impure metal of that kind
of which it is so principally composed, and be protected as such in the manner
herein-before described. The exact proportions of the metals in the protecting
alloy or compound metal are not essential to the production of some beneficial
effect; but in proportion as the galvanic tension or action is increased by
increasing the proportion of the metal positive in the galvanic circle, the
protecting alloy is destroyed more rapidly, and the metal to be protected in
some cases, such as in the sheathing on ships, has a tendency to become foul,
so as to compensate the advantages obtained by its protection from corrosion.
Where the metal required to be protected is to be immersed in or in contact
with a solution of neutral salt, which may be a more powerful menstruum, and
have a greater tendency to produce oxydation than sea water, the proportion
in the alloy of the metal most positive in the galvanic circle may be decreased
as the tendency to oxydation is increased. The protecting metal, both in
quantity and extent of surface, should be from one hundred to two hundred
parts of the metal to be protected; a considerably increased proportion
will not be injurious, but the protecting metal ought not to bear a less
proportion in quantity and extent of surface than one in four hundred
parts. The protecting metal may be attached to the metal to be protected
either by being rivetted or by being cast or melted on and united to
each separate portion of the metal to be protected. If rivets be used, the
surfaces of the metals to be united must be made smooth and clean, and
they must be so firmly fastened and united that no action by means of the
liquid can take place between the metals. The rivets should be negative in
the galvanic circle to the protecting metal, and positive to the metal to be pre-

page_text: tected, or else made of the same metal as that which is to be protected. Or,
the protecting metal may be firmly rivetted or united by melting to a small
portion of metal negative to it in the galvanic circle, and positive to the metal
to be protected or composed of the latter metal, and then nailed or screwed to
the metal to be protected with the negative surface in contact, the screws or
rivets not in any case to be positive to the protecting metal or negative to the
metal to be protected. In sheathing ships the protecting metal may be
attached to each separate sheet of metal employed on the upper and under
surface by rivetting, or the alley may be cast upon and brought into union with
it; or if one of the surfaces of the protecting metal shall have been firmly
rivetted to a thin piece of metal of the same size negative to it, and positive to
or a portion of the metal to be protected, it may then be attached with the
more negative surface in contact with the metal to be protected by nails or
screws passing through both the metals into the ship's side. The nails or
screws should be composed of the metal which forms the more negative
surface of the protecting metal, or of the same kind of metal as that which is
to be protected. In all cases the metal of the nails by which the sheathing is
fastened to the ship's side, and all other metals in contact with the sheathing
should have exactly the same electric character or relation in the galvanic
circle as the sheathing itself, or if it differs in that respect in any degree, it
should be positive to the copper or other sheathing; or where copper sheathing
is employed, nails may be used of an alloy of one hundred parts copper,
from seventy-five to ninety parts zinc, and either with or without a small pro-
portion of lead, taking care that the alloy shall be such that being tried by the
galvanometer, in manner before mentioned, it shall be positive to the sheathing
and continue to be so after immersion in sea water. Instead of applying the
protecting metal to each sheet of the sheathing, it may be fastened with the
precautions before described upon the sheathing in long strips of from six to ten
inches or more in breadth; one strip may be placed on each side of the keel
from stem to stern, and one or more strips joining it at the stern post, and
carried along cach side below the water line, and again joining the first
mentioned strip at the fore part. The last mentioned upper strip or strips
may be fastened by screws to the ship's side (the precautions above mentioned
having been first observed of closely uniting it by rivetting, melting, or other
wise to a negative metal), so that the upper strip or strips may be removed
for a time, in case of the ship fowling by the attaching of vegetable matter to
the bottom, and again replaced after the ship has become clean, or protecting
strips that are less positive may be substituted; or by another method sheets of
and

page_text: the protecting metal may be attached to the ship's side at various distances.
from each other upon the sheathing below the surface of the water, either per
manently or by screws, as herein-before described, in such a way that they may.
be removed at pleasure. Cisterns or tanks exposed to corrosion may be pro
tected by affixing to the surface beneath the liquid a protecting metal, as
herein-before described, either in picces or strips, to the bottom and each of
the sides; care must be taken that where water preserved is intended for
drinking, or the preparation of food, no metal must be used in the protecting
alloy or compound metal which may be injurious to health. Chain cables
may be protected by affixing to each link a portion of protecting metal, as
herein-before described; metals employed for other purposes in water, liable to
corrosion or oxydation, may be protected by attaching to them, in a situation
subject to the action of the water, pieces of alloys or compound metals formed
upon the principles, and attached with the precautions herein-before mentioned
and described.
The present Patent is, among other advantages, intended to prevent the
inconveniences arising from the methods hitherto adopted of protecting metals,
particularly in sea water, in which the galvanic action or tension between the
metals employed was too powerful, and for that purpose I claim as my Inven-
tion to use the alloys or compound metals, as herein-before described, not
limiting the alloy or compound metal to the exact proportions, herein-before
mentioned, so that the slight galvanic tension, herein-before described, is
established and continued.
And I further claim as my Invention the coating the under surface of the
protecting metal with a metal negative to the protecting metal, and positive to
thic metal to be protected, or with a portion of the protected metal itself, so as
to preserve the contact or communication of the protecting metal with tho
metal to be protected, and the consequent power in many cases of removing
and replacing the protecting metal at pleasure.
'In witness whereof, I, the said George Gwinnett Bompas, have hereunto
set my hand and seal, this Fourth day of May, in the first; year of the
reign of our Sovereign Lord William the Fourth; by the Grace of God,
of the United Kingdom of Great Britain King, Defender of the
Faith, and in the year of our Lord One
eight hundred and
thirty-one.
:

page_text: AND BE IT REMEMBERED, that on the Fourth day of May, in the
year of our Lord 1831, the aforesaid George Gwinnett Bompas canic before
our said Lord the King in IIis Chancery, and acknowledged the Specification
aforesaid, and all and every thing therein contained and specified, in form
above written. And also the Specification aforesaid was stamped according
to the tenor of the Statute made for that purpose.