AN IMPROVED PROCESS FOR PRESERVING IRON FROM CORROSION, AS PRODUCED BY THE INFLUENCE OF AIR AND SEA-WATER
Year: 1864

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PROVISIONAL SPECIFICATION left by Frederick Tolhausen at the Office
of the Commissioners of Patents, with his Petition, on the 18th March
1864. A communication from Mr: Charles de Bussy, Mining Engineer,
F.C.S., a person residing.at, No. 10, Avenue de Villars, Paris.
FREDERICK TOLEÄUSEN, formerly of 17, Faubourg Montmartre, but now
of 149, Boulevart Magenta, Paris, in the Empire of France, Civil Engineer
and Patent Agent, do hereby declare the nature of the said Invention for
AN IMPROVED PROCESS FOR PRESERVING IRON FROM CORROSION, AS PRODUCED BY
THE INFLUENCE OF AIR AND SEA-WATER," a communication from Mr. Charles de
Bussy, Mining Engineer, F.C.S., a person resident at No. 10, Avenue de
Villars, Paris, to be as follows:-
The means hitherto employed for preserving iron from any corrosive actions
are based either on galvanic processes or on the use of coatings intended to
resist said corrosive actions. When substances are thus applied in a
mechanical way to preserve the surface of iron they offer a very slight
adhesion. Moreover, in many cases, according to the nature of the metallic
oxide used for the coating, they will exert a direct corrosive action, such as

page_text: takes place with minium when applied to the hulls of iron-built vessels. Acting
upon these data, I have come to the conclusion that in order to obtain a most
satisfactory result in preserving iron, a coating must be used whose adhesion
shall be the result of chemical action on the metal itself. Amongst the
various matters that will fulfil this condition I prefer using the fusible and
insoluble chemical compounds, they both protecting the surface of the iron,
and filling up, by reason of their fusibility, those imperceptible fissures and
cavities which always occur in wrought iron, owing to the porous nature of
the metal, and to the imperfections unavoidably arising from the forging
process.
A great number of compounds may be used each answering the purpose of
this Invention, as above set forth. In order to shew clearly its nature and
how it is or may be carried into effect, I will now describe the manner in
which I employ one particular compound by which I have obtained the best
result.
The process which I consider the most simple and reliable consists in
subjecting the iron pieces to be preserved to the action of phosphorus at a
high temperature, so as to produce on their surface a thin layer or coating of
melted phosphide of iron. This coating proves to be very adhesive, and is
hardly acted upon by the corrosive agents to which iron is commonly exposed.
This operation may be effected by exposing the red-hot iron direct to the
vapours of phosphorus, but a more simple and economical way is by heating
the pieces in cases or chambers similar to those of converting furnaces
imbedded in a brasque or mixture composed of charcoal or coke dust,
impregnated with a solution of acid phosphate of lime. Pieces of a large
size may also be brought to a welding heat, and then be laid on a bed of
brasque composed as aforesaid and well dried and covered up with the same
materials. The heat radiated by the piece is sufficiently powerful to cause
the distillation of the phosphorus, and its combination with the iron. This
preserving process may be advantageously applied in many instances, such as
for plate iron for ship-building, anchors, gun carriages, water tanks, and so
forth. It is peculiarly adapted for iron plating or iron shields, for preventing
the rapid deterioration of which no efficient means has been devised
hitherto.
I wish it to be distinctly understood that I do not confine my process to the
use of phosphorus only, but I claim in like manner any other body acting in
the same way, such as arsenic, antimony, and so forth.
The mode of applying these various substances will necessarily have to be

page_text: somewhat modified according to their reactions and the nature of the com-
pounds from which they are derived. Arsenic, for instance, will be applied
in the same way as phosphorus, with the only difference that the brasque shall
be composed of a mixture of charcoal and arsenious acid with lime, carbonate
5 of lime, or an alkaline carbonate.