CERTAIN IMPROVEMENTS IN PROTECTING CAST AND WROUGHT IRON, AND STEEL, AND OTHER METALS FROM CORROSION AND OXIDATION, AND IN PREVENTING THE FOULING OF IRON SHIPS OR SHIPS SHEATHED WITH IRON, OR OTHER SHIPS, OR IRON BUOYS, IN FRESH OR SEA WATER
Year: 1841

page_text: MALLET, of Dublin, Engineer, send greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Letters Patent under the Great Seal of Great Britain, bearing date at West-
minster, the Seventh day of July, in the fifth year of Her reign, did, for
Herself, Her heirs and successors, give and grant unto me, the said Robert
Mallet, Her especial licence, full power, sole privilege and authority, that I,
the said Robert Mallet, my exors, admors, and assigns, and such others as
I, the said Robert Mallet, my exors, adññiors, or assigns, should at any time
agree with, and no others, from time to time and at all times thereafter during
the term of years therein expressed, should and lawfully might make, use,
exercise, and vend, within that part of Her Majesty's United Kingdom of
Great Britain and Ireland called England, Her Dominion of Wales, Town of
Berwick-upon-Tweed, the Islands of Guernsey, Jersey, Alderney, Sark, and
Man, and also in all Her Majesty's Colonies and Plantations abroad, my
Invention of "CERTAIN IMPROVEMENTS IN PROTECTING CAST AND WROUGHT IRON,
AND STEEL, AND OTHER METALS FROM CORROSION AND OXIDATION, AND IN PREVENTING
THE FOULING OF IRON SHIPS OR SHIPS SHEATHED WITH IRON, OR OTHER SHIPS,
OR IRON BUOYS, IN FRESH OR SEA WATER;" in which said Letters Patent is
contained a proviso that I, the said Robert Mallet, shall cause a particular
description of the nature of my said Invention, and the manner in which the
same is to be performed, under my hand and seal, to be inrolled in Her
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

page_text: and by the same, reference being thereunto had, will more fully and at large
appear.
NOW KNOW YE, that in compliance with the said proviso, I, the said
Robert Mallet, do hereby declare that whereas by the best methods of zincing
heretofore in use for protecting articles of cast and wrought iron, and steel,
and other metals, and more especially ships built of iron or sheathed with
iron, from corrosion and oxidation, the iron or other metal is left bare in a
number of spots by the subsequent collection of rust, upon which the electro-
chemical protective power of the zinc in respect of the iron is almost entirely
neutralized; and whereas, also, there is a difficulty in causing the iron or other
metal and zinc to unite except at temperatures above the melting point of zinc,
which causes a great loss by oxidation of the zinc, and a very imperfect
adhesion of that metal; and whereas it has been further found that iron
covered with zinc when immersed in sea water and certain fresh waters soon
gathers to itself a coating of carbonate of lime, which is not only destructive
of the protective power of the zinc, but affords a favorable surface for the
attachment and growth of marine animals (generally of the moluscous and testa-
ceous classes) and aquatic plants, whereby the vessel becomes what is generally
called "fouled;" now, the nature of my said invented improvements consists
in the employment of certain new methods or processes and certain new alloys,
paints, coatings, and varnishes, whereby the protected metals and protecting
metals or metallic alloys are presented to each other in a state of such
exceeding purity and under such favorable circumstances for combination that
no part of the metal sought to be protected is left bare, and not only all
corrosion and oxidation but all fouling from the accrescence of calcareous
matters, and consequent adhesion of marine animals and aquatic plants,. is
completely prevented. And I declare that the manner in which the same
is to be performed is fully set forth in the following description thereof, that is
to say:-
I show in the description which follows the manner in which the said
improvements are to be applied to the protection of ships built of iron, (the
most valuable and important of all the purposes to which they are applicable,)
from which description, together with the additional explanations appended
thereto and herein-after contained, the manner of applying them to other
articles may be readily understood.
And with respect to the plates and ribs of iron employed in the construction
of iron vessels, I first carefully cleanse them from all adhering oxide, for which.
purpose I immerse then edgewise (or in such an inclined position that the
detached scales of oxide can readily fall off in a suitable vessel of wood,

page_text: pottery, stone, or lead, containing dilute sulphuric acid, of the specific gravity
of about 1.300 at sixty degrees of temperature of Fahrenheit's thermometer,
or dilute hydrochloric acid of the specific gravity of about 1.060 at sixty
degrees of temperature of Fahrenheit's thermometer, formed by diluting these
acids respectively, as they are usually found in commerce, with rather more
than an equal bulk of water. As it is of importance that the scales of oxide
should be detached as rapidly as possible the diluted acid should be warmed,
and this may conveniently be effected by means of a steam jacket round the
vessel, or by blowing steam into the acid. The acid vessel, or "cleansing bath,"
as it may be termed, should be so constructed for operations on a great scale
that the lower portions of the acid and the scales which are precipitated can
be occasionally withdrawn to prevent waste of acid, or the cleansing process
from being inconveniently protracted. The iron must be wholly not partially
immersed, and the bubbles of gas formed on its surface must be free to ascend
in the fluid and escape; as soon as the scales of oxide have become detached or
loosened the articles are to be removed from the "cleansing bath," thrown into
or washed with cold water, and struck or hammered to shake off and detach
the scales. In the case of flat boiler plates they may be advantageously
passed backwards and forwards through the machine known to boiler makers
as "a mangle." The surfaces of the iron are then to be thoroughly scoured
by hand or by any suitable machinery, with sand or emery, or with pieces of
grit stone, while exposed to a small running stream of water, until they appear
quite clean and of a bright metallic lustre. The articles are now, before being
allowed to dry, to be plunged into a "preparing bath," consisting of the
following mixture:-A saturated cold solution of chloride of zinc is made by
dissolving zine or its oxide in hydrochloric acid, or by any other known means;
to this is added an equal bulk of a saturated cold solution of sal aminoniac, and
to the mixed solutions as much more sal ammoniac in the solid state is ad led"
as they will dissolve; or these solutions may be made and mixed hot, and the
solid sal ammoniac then added, but the addition of some cold water will then
be requisite to dissolve the whole of the salts so formed. The bath may also be
formed of sulphate of zinc and sulphate of ammonia, or acetate of zinc and
acetate of ammonia, or of any other soluble double salt of zinc and ammonia,
or salt of manganese and ammonia; the nitrates of zinc and ammonia are
the least advantageous, and none answer the purpose so well according to my
experience as the chloride of zinc and sal ammoniac first before directed to be
used; no free acid should be present in these solutions. As soon as the
surfaces of the immersed articles appear covered all over with minute bubbles of
gas, they are then in a fit state for combining with the metallic alloy, with which

page_text: they are next herein-after directed to be coated; but they may be allowed to
remain in the "preparing bath" for any convenient length of time without
injury or prejudice to the subsequent processes. The metallic alloy last herein
referred to is prepared in the following manner :-A quantity of zine is melted in
a suitable vessel (one formed of pottery or stone I find to answer best), and when
it is in a state of fusion mercury or quicksilver is added, in the proportion of
two hundred and two parts of mercury to twelve hundred and ninety-two parts
of zinc (both by weight), being in the proportion of one atom of mercury to
forty atoms of zinc, both upon the hydrogen scale. The two metals are well
stirred or mixed together with a rod of dry wood or of iron coated with clay,
and when this has been done, there is added one or the other of the metals
known to chemists and others as potassium and sodium (the metallic bases of
which the well-known alkalies, potash and soda are oxides), in the proportion
of one pound or thereabouts of potassium or sodium to every ton weight
of the alloy; or, in some cases, less will suffice of zinc and mercury. Either
potassium. or sodium will answer the purpose, but I prefer the latter, as
more easily obtained, and more manageable. Whether it is potassium
or sodium which is used, it is removed from the naptha or other fluid in
which it is customary to keep these metals, in order to preserve them
from oxidation, in small portions of not more than half an ounce at a time, and
by means of a small inverted cup of wood formed on the end of a stick, thrust
rapidly below the surface of the alloy of zinc and mercury, so as to avoid any
waste or combustion of the alkaline metal. A triple alloy is thus formed of
zine, mercury, and sodium or potassium, which having been again stirred and
mixed with the rod of dry wood, or of iron coated with clay, is now ready for
covering or coating the prepared iron. The combination of these metals is
facilitated, and their oxidation on the surface retarded by pouring upon their
fluid surface some of the liquor of the "preparing bath," or strewing upon it
some of the salts dissolved in that liquor in a dry state. The plates or ribs of
iron are now to be taken out of the "preparing bath," permitted to drain for a
few seconds, and, while still wet with the liquor of the preparing bath, immersed
in the triple alloy in a state of fusion. As soon as they have acquired the
temperature of the bath of alloy, they are to be withdrawn from the metallic
bath edgewise or endwise, when they will be found covered with a perfectly
uniform and coherent coat or surface of the alloy. The affinity of this alloy
for iron, however, is so intense, and the peculiar circumstances of surface
induced upon the iron presented to it by the "preparing bath" are such; that
care-is requisite, lest by too long an immersion the plates are not partially or
wholly dissolved. Indeed, where the articles to be covered are small, or their

page_text: parts minute, such as wire or nails, or small chain, it is necessary before
immersing them to permit the triple alloy to dissolve or combine with some
wrought iron, in order that its affinity for iron may be partially satisfied, and
thus diminished. At the proper fusing temperature of this alloy, which is
about six hundred and eighty degrees of Fahrenheit's thermometer, it will
dissolve a plate of wrought iron of an eighth of an inch thick in a few
seconds. No sputtering is produced by the immersion of the iron wet from the
preparing bath into the alloy, but care is to be taken that there are no hollow
places or cavities in the articles immersed which the alloy cannot wholly fill,
lest in such case steam may be generated below the surface of the metal, and'
a dangerous explosion be thereby occasioned. It is desirable that the melting
vessels should be as deep and expose as small a surface as the nature of the
articles to be immersed will allow. At the moment of iminersion of the articles
the surface of the alloy is to be cleansed of all dross or oxide by a wooden
skimmer. As soon as the iron plates or ribs are withdrawn.from the alloy or
metalling bath they are to be plunged into cold water, and well washed therein.
The surface of the iron is now in a condition permanently to resist corrosion
and oxidation in air, or in salt or fresh water. All the foregoing operations are
best performed upon the plates or ribs after they have been bent and fitted to
their places, and the plates have been rivetted together into large pieces of
eight to ten feet square, or more. When again put "into frame," or placed in
their respective positions in the ship's hull, they are to be united by rivets
counter-sunk from the outside; and consequently headed inside the vessel.
The counter-sunk heads of these rivets are to be also coated with the triple
alloy in the manner herein-before described, and tongs are to be provided of
iron, having a very large mass of metal in their jaws, between which a hollow
seat, by the shape and size of the countersunk rivet head, is to be formed to
receive it. An alloyed rivet being seized by a pair of such tongs, may have its
point heated to a rivetting or welding heat without injuring the coat of alloy.
upon its countersunk head, for the heat is carried off from the latter so fast
by the contact of the large mass of iron in the jaws of the tongs, which are to
be cooled occasionally, as to prevent the head of the rivet becoming hot during
the heating of the point in a common smith's fire. The hull of the iron vessel
being thus completed, and wholly covered with the alloy, is then to receive a
coat of varnish all over, of either of the compositions about to be described. If
possible, this varnish should be laid on with a spatula, or thin flexible blade of
liorn, or some such material, as a brush produces minute air bubbles, which
leaves spaces uncovered on the drying of the varnish. The varnish will dry,
or get hard and coherent, at ordinary temperatures, but where practicable it is.

page_text: desirable to expose it for some hours to a temperature of about three hundred
degrees of Fahrenheit, which gives it greater adhesion and durability. The
iron surfaces may be warmed in successive portions by heat radiated from
"chauffers" or open fires of coke, or by any other convenient means, or the
heating of the varnish may be altogether omitted. The varnish may be either
of a composition which I term Number 1, or of another, which I term Number
2. The composition Number 1 is formed as follows:-Take fifty pounds of
foreign asphaltum, melt and boil it in an iron vessel for three or four hours,
add gradually sixteen pounds of red lead and lytharge ground together to a
fine powder in equal proportions, with ten imperial gallons of drying linseed
oil, and bring all nearly to a boiling temperature; melt in a separate vessel
eight pounds of gum anime (which need not be of the clearest or best quality),
add to it two imperial gallons of drying linseed oil boiling, and twelve pounds
of caoutchouc softened or partially dissolved by coal tar naptha (as practised
by the makers of waterproof cloth). Mix the whole together in the former
vessel, and boil gently until, on taking some of the varnish between two
spatulas, it is found tough and ropy. When this body is quite cold it may be
thinned down with from thirty to thirty-five gallons imperial of turpentine, or
of coal naptha, which will make it ready for use. I consider this to be the
best varnish I am acquainted with for this purpose. It is not acted on when
dry and hard by any moderately diluted acid, or caustic alkali. It does not
by long immersion combine with water, and so form a white and partially
soluble hydrate, as all merely resinous varnishes, and all oil paints do. It is,
moreover, so elastic that a plate covered with it may be bent for several times
without its peeling off; and lastly, it adheres so fast that nothing but a sharp-
edged instrument will scratch it off the surface of iron. The composition
Number 2 is of a cheaper sort, but not quite so good. Common coal or gas
tar is to be boiled in an iron cauldron at so high a temperature that the smoke
from it is of a yellow dun colour, or the tar is to be caused to flow through
red-hot iron tubes. The boiling passage through the tubes is to be continued
until the residue is a solid asphaltum, breaking with a pitchy fracture. It is
essential that the boiling should be carried on at this high temperature as the
permanence of the varnish in water depends upon the tar having been sub-
mitted to the temperature at which napthaline is formed by the decomposition
or breaking up of the original constitution of the tar. Take fifty-six pounds
of this coal tar asphaltum, melt it in an iron vessel, and ten imperial-gallons of
drying linseed oil, ground with twenty-five pounds of red lead and lytharge in
equal proportions; add to the whole when well mixed, and after boiling
together for two or three hours, fifteen pounds of caoutchouc softened or par-

page_text: tially dissolved by coal naptha (as before described), and when cold mix with
twenty to thirty. gallons of turpentine or coal naptha, which will make the
varnish ready for use. Several coats of either of these varnishes may be
laid on, if thought desirable, but two coats will generally be found sufficient
for every purpose. The last operation to be performed in order to prevent
what is called "fouling," is to paint the vessel all over (above the varnish)
with a strong-bodied thick paint, which, from its life-destroying qualities,
I call the zoofagous paint. It is composed of drying linseed oil, red lead, and
sulphate of barytes (or white lead may be used, but not so advantageously,)
and a little turpentine; to every one hundred pounds of these ingredients when
mixed is to be added twenty pounds, or thereabouts, of oxychloride of copper,
and three pounds of a mixture composed of hard yellow soap melted with an
equal weight of common rosin and a little water. The color originally. sold
in commerce under the name of "Brunswick green, was an oxychloride of
copper, but the present Brunswick green of commerce is a different thing and
will not answer. The oxychloride of copper may be obtained at a cheap rate
by various known methods, which it is unnecessary here to detail. When the
whole of the hull of the vessel has been done over with this paint it must then
be permitted to dry and harden for three or four days before the ship is floated
out of dock. The entire series of operations are now completed, and the hull
of an iron ship so treated will resist all corrosion from the action of air and
fresh or sea water, and not be liable to "fouling" by the adhesion of marine
animals and plants.
The power of the zoofagous paint to prevent "fouling". arises from the fact
that the insoluble or difficulty solube salts of copper and of certain other
metals are so noxious to the life of marine or aquatic animals and plants
which generally attach themselves to ships' bottoms, that they will not adhere
or grow upon a surface so treated. The paint, therefore, is only a vehicle for
poisonous matter, for which purpose it is requisite that it should have sufficient
adhesion to resist the ship's motion, but still should have a slight degree of
solubility in water, so that the poisonous matter may be taken up by the
absorbent or capillary vessels of any adhering animal or plant. This latter
property is given it by the addition of the resinous soap, the proportion of
which should be varied to suit the climate to which a ship is going, more
being used in frigid and less in tropical climates. I. prefer using the oxy-
chloride of copper, and have found it by much the most efficacious, but: any
insoluble, or difficultly soluble salt of copper, mercury, arsenic, or antimony, or
any combination of these, whether soluble or insoluble, may be substituted for
it; and though I deem it advisable that iron employed for the building of iron

page_text: In
ships should undergo all the processes herein-before described, I desire that it
should be understood that they are not all equally essential to the protection
thereof, and that the same effects may be produced, though attended with less
favorable circumstances, by the adoption of a part only of the said processes.
For, supposing the plates and ribs. of iron were merely coated with the triple
alloy of zinc, mercury, and potassium or sodium, without the addition of the
protective varnish and zoofagous paint, it is certain that on the exposure
of this alloy to the action of air and water the positive metal at the
surface would be first acted on, and the surface become shortly covered with a
very thin coat of amalgamated zinc, which is known not to be acted upon
by fluid menstrua (except under peculiar conditions which do not exist
in the case here supposed), and does not, as I have found by experiment,
gather to itself when exposed to sea or fresh water any of that calcareous
coating which is productive of the fouling of vessels. The advantage gained
by varnishing over this triple alloy coating is of a twofold nature.
the first place, it serves as a mechanical protection to the coating, and
thereby to encrease its durability; and, secondly, it shields the alloy from
contact with the zoofagous paint, some of the ingredients of which would exert
an injurious chemical action on the alloy. The office, therefore, of the triple
alloy is simply to prevent corrosion and oxidation (including, where used by
itself, that of preventing the formation of a calcareous adhesions); that of the
varnish, to protect the triple alloy; and that of the zoofagous paint, to prevent
fouling by the destruction of any marine animals or aquatic plants which may
seek to attach themselves to the protected surfaces. And by attending to these
distinctions any person of ordinary skill will readily understand to what extent
these processes should be followed, or how they should be varied for the
purpose of protecting other articles than the plates and ribs of iron vessels from
oxidation and corrosion, or from fouling; where the addition of the zoofagous
paint is not required to prevent fouling, as in the case of articles exposed to
the action of the atmosphere only, any desirable color may be given to the
protecting varnish by a mixture of colouring materials, but care must be taken
that these colouring materials consist of peroxides not liable to be acted on by:
air or moisture. The best method to adopt, however, with such articles is to
pay the varnish all over with a coat of oil paint; and though I have herein-
before directed that the bath of the triple alloy should be employed at the
fusing temperature, I declare that I do not confine myself to the use of it at
that temperature, for by the addition of a larger portion of mercury than that
I have herein-before prescribed, articles of cast or wrought iron or steel may
be coated with that alloy at a lower temperature, and even in a cold state, by.

page_text: means of simple contact and friction. I declare further, that instead of using
any of the processes herein-before described for the protection of iron, steel,
and other metals from oxidation and corrosion, I sometimes make use of a
very thin coating of palladium, applied in the state of an amalgam with
mercury, or by any other means, first cleansing and preparing the articles
by means of the double salts of zinc and ammonia, or of manganese and
ammonia, in the manuer herein-before particularly described.
And having now described the nature of my said invented improvements,
and the manner in which the same are to be performed, I declare that I do
not claim, as of my Invention, the cleansing of the surfaces of articles of iron
and other metals by plunging them in the cleansing bath of acid liquids, the
same being already known and practised; but that what I claim is, the parti-
cular method of effecting the same, herein-before described, and more particu-
larly the use of the double salts of zinc and ammonia, or of manganese and
ammonia, for the purposes of cleansing or preparing metals in order to alloy or
unite the same in any way with each other, or for coating one metal with
another or with a combination of other metals.
I declare further, that I do not claim the use of an alloy of zinc and
mercury alone for the purpose of preserving iron, the same having been
already used; but that I claim the use for that purpose of all alloys of
zine and mercury with potassium or sodium, and of all alloys in which zinc,
mercury, and iron are combined with potassium or sodium, whatever may be
the proportions in which each of the said metals is employed.
I further claim the use of potassium and sodium in combination with other
metals to reduce small portions of suspended oxides, and so promote the union
of such metals or aid in alloying them, or for the purpose of coating one metal
with another, and thereby preventing oxidation and corrosion, both as herein-
before described.
I declare, also, that I do not claim the particular protective varnishes,
composed of asphaltum and caoutchouc, as herein-before described, as several
analagous compounds have been long in use; but that I claim the use of
these or of any other varnishes for the purpose of protecting iron or other
metals from corrosion when employed in combination with a coating of the
triple alloy herein-before described, and when such coating is added to the
iron, while the former is in a state of fusion, or when used in combination with
a covering of zinc, lead, or tin, or any mixture of these metals, by whatever
process put on or caused to adhere to the iron or other metals.
I claim further, not only the use of the zoofagous paint, the composition of
which is herein-before particularly described, but the use of all paints or
varnishes, however made, possessing qualities destructive of animal and

page_text: vegetable life, or injurious to the existence and adhesion of marine animals and
aquatic plants to ships' bottoms or other surfaces, whether consisting of iron or
of any other metal, or of wood or any other material, when the same are rendered
poisonous or injurious by admixture of any of the insoluble or difficultly soluble
salts of the metals, copper, mercury, arsenic, or antimony, or of any salts or
combination of salts of these metals with each other or with those of other
metals, and when the same are used for the purpose of preventing fouling,
whether they are applied to iron ships or ships sheathed with iron, or partially
sheathed with iron, or to other bodies of iron, floating or immersed in sea or
fresh water, and whether, also, they are used in combination with the pro-
tecting triple alloy and varnish herein before described, or either of them,
or in combination with any other protecting agent, or applied separately and
without the accompaniment of any other projecting agent whatever.
I claim, moreover, the use and application of the said zoofagous and other
paints similarly compounded, to ships or other bodies floating or immersed in
sea or fresh water, and made of timber or any other material sheathed with
copper and electro-chemically protected by the contact of zinc according to the
plan suggested by Sir Humphry Davy, inasmuch as by the addition of such
paint or paints the copper is both saved from corrosion and also from fouling,
which fouling is not by the use of the zinc alone to be prevented.
And I declare, that I claim generally the application of the three several
processes herein-before described; namely, the coating with the triple alloy,
the varnishing, and the painting, to all articles or things, whether of cast
iron, wrought iron, or steel, or of any combination of these metals, to which
they may be applicable, as well as to ships, whether all three or any two of s
them are used in combination, or they are used separately.
And, finally, I claim the use of the metal called palladium, for the purpose
of protecting cast iron, wrought iron, or steel, or any combination of these
metals, from oxidation and corrosion, whether applied to these metals in the
state of an amalgam with mercury with the aid of the double salts of zinc and
ammonia, or of manganese and ammonia, or by any other process.
In witness whereof, I have hereunto set my hand and seal, this Thirtieth
day of December. One thousand eight hundred and forty-one

page_text: This is the Specification referred to in the affidavit of Henry Desborough,
sworn before me, this Seventh day of January, One thousand eight hundred
and forty-two.
R. RICHARDS.
Henry Desborough, of the Atlas Assurance Company, Cheapside, in the
City of London, Esquire, maketh oath and saith, that he is well acquainted
with the manner and character of the handwriting of George Studdert,
Esquire, a Justice of the Peace, at Dublin, within that part of the United
Kingdom of Great Britain and Ireland called Ireland; and this deponent
further saith, that the name or signature, "Geo. Studdert," with the addition,
"Magistrate for Dublin," set, subscribed, or written upon, or endorsed on the
Specification marked A, hereunto annexed, and dated the Thirtieth day of
December, One thousand eight hundred and forty-one, and purporting to be
executed by "Robert Mallet," whereby it is stated that the said Specification
was acknowledged by the said Robert Mallet before the said George Studdert,
on the said Thirtieth day of December, One thousand eight hundred and forty-
one, at Dublin aforesaid, is of the proper handwriting of the said George
Studdert; and that the said George Studdert, at the time of setting or
subscribing his name to the said Specification in manner above stated, was
and now is, to the best of the knowledge and belief of this deponent, one of
the Justices of the Peace acting in and for that part of the United Kingdom
of Great Britain and Ireland called Ireland.