IMPROVEMENTS IN THE TREATMENT OF ARTICLES OF CAST IRON FOR THEIR PROTECTION AND ORNAMENTATION."
Year: 1880

page_text: LETTERS PATENT to James John Shedlock, of Uxbridge, in the County of
Middlesex, for an Invention of "IMPROVEMENTS IN THE TREATMENT OF
ARTICLES OF CAST IRON FOR THEIR PROTECTION AND ORNAMENTATION."
PROVISIONAL SPECIFICATION left by the said James John Shedlock at the
" IMPROVE-
Office of the Commissioners of Patents on the 30th December 1880.
JAMES JOHN SHEDLOCK, of Uxbridge, in the County of Middlesex.
MENTS IN THE TREATMENT OF ARTICLES OF CAST IRON FOR THEIR PROTECTION
AND ORNAMENTATION."
The object of this Invention is the treatment of articles of cast iron in order that
they may not only resist the action of moisture and atmospheric influences, but
also other corrosive agents, whether solid, liquid, or gaseous, and without in any
way altering the delicacy of form and outline possessed by the article before
treatment.
In the methods as at present practised for the preservation of articles of iron
(namely, coating or covering them with paints, japans, enamels, the electro
deposition of less oxidizable metals, or the formation of a film of magnetic oxide
on their surfaces), the protecting coat is very thin and not able to withstand much
wear and tear, or, when thick, the fineness and character of the casting is entirely
destroyed.
In consequence of these protection materials being only laid on to the surface of
the iron, the slightest abrasion renders the iron accessible to the action of oxidizing
agents.
For the purpose of overcoming the difficulties attending the perfect preservation
of articles of cast iron it is proposed by this Invention to treat such articles by
subjecting them in suitable vessels to the action of any acid solution possessing the
properties of dissolving iron, and forming therewith soluble salts. Cast iron being
a combination of iron and carbon or graphite, the action of the acid solution is such
that the surface iron is dissolved, leaving a porous skin of carbon or graphite of
tenacity sufficient in itself to resist considerable wear and tear, and the thickness

page_text: of which may be regulated by the length of exposure of the article to the action of
the acid, and at the same time maintaining the exact outer form and delicacy of
contour which the articles possess before treatment. The carbon or graphite skin
thus formed is not a mere layer or detachable film, but forms a continuous substance
with the body of the casting. When by the action of the acid on the iron the graphite
skin has acquired the desired thickness, the articles may be taken from the vessel and
treated for the removal of the iron salt from the pores of the graphite skin
preparatory to subjecting them to the preservative solution. If preferred however
the vessel containing the articles may be closed up air tight and the acid solution
removed therefrom by means of a pump or other contrivance, in which case a more
or less perfect vacuum is formed in the vessel, and as a consequence assist to remove
the iron salt in solution from the pores of the graphite skin. Hot or cold water, or
if preferred steam, may now be injected into the vessel and allowed to pass through
it until the pores of the graphite skin are freed from the salt of iron. The water
is now removed from the vessel and a vacuum formed therein which, with the aid
of heat, will more effectually remove any water or its vapour. The articles are
then ready to receive the protecting solution which, on being allowed to enter the
vessel, fills up the pores of the graphite skin and excludes any oxidizing agent from
contact with the iron. When it is desired to prepare cast iron articles so that they
may resist the action of corrosive agents, then the solution applied must possess
that property, such, for instance, as a solution of bitumen or resin in a volatile
solvent, upon the evaporation of which the bitumen or resin is deposited in the
pores of the graphite skin. For the purpose of ornamentation or preservation it
may in some cases be desirable to enamel such articles of cast iron treated as
described, in which case the articles having the porous graphite skin are coated or
immersed in a solution containing such materials as will when subjected to heat
liquify and not only fill up the pores of the graphite skin, but when desired cover
its entire surface. The less oxidizable metals may also be electro deposited in the
pores and on the surface of the graphite skin by any known process, when it will
be found that the metal so deposited is strongly adherent, forming a permanent
protection. Other metals may also be deposited in the pores of the graphite and
on the surface of the iron by immersion in their solutions, or by their reduction at
elevated temperatures, thus filling the pores and covering the surface of the graphite
skin with a protective and ornamental film of the reduced metal.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said James John Shedlock in the Great Seal Patent Office on the 30th
June 1881.
"IMPROVE-
JAMES JOHN SHEDLOCK, of Uxbridge, in the County of Middlesex.
MENTS IN THE TREATMENT OF ARTICLES OF CAST IRON FOR THEIR PROTECTION
AND ORNAMENTATION."
The said Invention has for its object the treatment of articles of cast iron in
order that they may be protected from oxidation, whether caused by their exposure
to moisture and atmospheric influences or from their contact with the more corrosive
agents. To carry the said Invention into effect the articles of cast iron are exposed
in suitable vessels to the action of agents which possess the properties of dissolving
iron and forming therewith soluble salts, such, for instance, as dilute hydrochloric
or sulphuric acids. Now, cast iron being a combination of iron with carbon or
graphite, it follows that when articles of cast iron are exposed to the action of a
dissolving agent, the surface iron is removed and a porous skin of carbon or graphite
is formed on the article, and as carbon or graphite is practically unaffected by
corrosive agents of the most energetic nature, all that is necessary, therefore, in
order to protect the body of the iron is to fill up the pores of the graphite skin with
a material possessing like properties with the graphite. The materials applicable
for this purpose are pitch, resins, india-rubber, and gutta-percha dissolved in suitable
solvents. When the graphite skin has acquired the desired thickness by reason of
the cast iron articles having been exposed to the action of the dissolving agent they
are removed from the vessel and placed in air tight chambers, in which the articles
are subjected to the action of hot or cold water or steam for the purpose of removing
the iron salt which has formed in the pores of the graphite skin. As soon as it is
ascertained that the iron salt in solution is removed from the pores of the graphite
skin the solution water, &c., is removed from the air tight vessel, and heat is applied
to its exterior for the purpose of vapourizing any water remaining and removing
the vapour thus formed by means of a pump or other contrivance. A more or less
perfect vacuum being formed in the air tight vessel containing the cast iron articles,
communication is opened with the reservoir containing the solution of pitch, resin,
india-rubber or gutta-percha, which is forced into the air tight vessel by the pressure
of the atmosphere, and the pores in the graphite skin are filled with the solution, so
that when the solvent is vapourized and withdrawn from the vessel the solid
material is deposited therein, thus producing a perfectly protective skin or covering.
Cast iron vessels or apparatus prepared as described are capable of being used for
the production or treatment of the most corrosive acids, and possess advantages
which will enable them to replace the more costly and less efficient apparatus as
now manufactured in glass, earthenware, and other expensive materials, both as to
their greater durability and economy. Articles of cast iron may also be used for
electrical apparatus, such, for instance, as battery troughs, in which case the surface
and pores of the graphite skin must be covered and filled with an insulating
material prepared as a solution and the solvent removed, as hereinbefore described.
In some cases it is desired not only to protect articles of cast iron from oxidation
but to impart to their surfaces an ornamental appearance; this may be secured by
using pigments in combination with the protective solution, or it may be by the
use of colored enamels. When it is desired that the pores and surface of the
graphite skin shall be filled and covered with an enamel, then it is not absolutely
necessary to remove the iron salt from the pores of the graphite skin, but the
articles may be removed from the vessel containing the dissolving agent and at
once placed in a vessel containing a solution capable of producing a double

page_text: decomposition with the iron salt, suitable solutions for this purpose being the
silicate of soda and the salts or oxides of lead. When silicate of soda solution
is used, and the dissolving agent has been dilute hydrochloric acid, double
decomposition of the two salts takes place, chloride of sodium being formed and
remaining in solution, and silicate of iron being insoluble fills up the pores in the
graphite skin. The surface of the article is now covered with an enamel of the
desired color, which, upon being subjected to heat, fluxes, and in combining with
the silicate of iron contained in the pores of the graphite skin will form a hard
vitreous enamel capable of resisting rough usage and effectually protecting the
cast iron article from oxidation. When it is desirable to produce an enamel on the
surface and in the pores of the graphite skin which shall flux at a low temperature,
then instead of employing the silicate of soda, the oxides or salts of lead may be
used, which, although producing an enamel protective against oxidation under
ordinary conditions, yet is not sufficiently hard to resist heavy usage. The pores
and surface of the graphite skin may be filled and covered with the less oxidizable
metals by means of electro-deposition, or they may be deposited from their solutions
by simple immersion therein of the cast iron articles, or the metals may be reduced
from their salts or oxides at elevated temperatures.
An example of such reduction suitable for the protection of an article of cast
iron is when the pores and surface of the graphite skin are filled with an oxide of
lead and subjected to heat; the oxygen of the lead oxide combines with the graphite
forming carbonic anhydride or oxide, and the lead is deposited in the metallic state
in the pores of the graphite skin. Other metallic salts and oxides are capable of
producing like results under favorable conditions.
Having now explained the nature of my said Invention and the method of
* carrying the same into effect, I would have it understood that I do not confine
myself to the precise details and materials described, as they may be varied to suit
special cases, but that which I claim and desire to have secured to me by the grant
of Letters Patent is, the treatment of articles of cast iron for their protection and
ornamentation by the formation on their surfaces of a graphite skin, the pores and
surface of which are filled and covered with a material capable of resisting oxidizing
agents, substantially as and for the purposes hereinbefore described.
In witness whereof, I, the said James John Shedlock, have hereunto set my
hand and seal, this Thirtieth day of June, in the year of our Lord One
thousand eight hundred and eighty-one.
JAMES JOHN SHEDLOCK. (L.S.)