IMPROVEMENTS IN COATING OR COVERING METALS FOR THE PURPOSE OF PREVENTING OXIDATION
Year: 1846

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ANDREW
SMITH, of Princes Street, in the County of Middlesex, Engineer, send
greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Royal Letters Patent under the Great Seal of Great Britain, bearing date at
Westminster, the Eleventh day of February, in the ninth year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the said
Andrew Smith, Her especial license, full power, sole privilege and autho-
rity, that I, the said Andrew Smith, my executors, administrators, and assigns,
and such others as I, the said Andrew Smith, my executors, administrators, 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 "IMPROVEMENTS IN COATING OR
COVERING METALS FOR THE PURPOSE OF PREVENTING OXIDATION;" in which said
Letters Patent is contained a proviso obliging me, the said Andrew Smith,
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 enrolled 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 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
Andrew Smith, do hereby declare that the nature of my said Invention, and

page_text: the manner in which the same is to be performed, is particularly described
and ascertained in and by the following description thereof, reference being
had to the Drawings hereunto annexed, and to the letters and figures marked
thereon (that is to say) :-
This Invention of Improvements in Coating or Covering Metals for the
Purpose of Preventing Oxidation relates to that process of coating metals
whereby the articles to be preserved from oxidation are plunged into a bath of
molten zinc, and there receive a coating of that metal.
My improvements consist in a new mode of transmitting heat (from the
furnace employed for melting the metal) to the vessel which contains the
zinc. According to the ordinary method of melting the zinc, and keeping it
in a molten state to receive the articles which are required to be coated, the
flame of the fire is made to play round the sides only of the pan or vessel
containing the zinc, for the refuse particles of the zinc falling to the bottom
of the pan soon form a thick incrustation thereon; the result, therefore, of
allowing the flame to play upon the under surface of the pan would be to
quickly burn out the bottoni. Besides the great loss of heat which is thus
'occasioned, the direct action of the fire upon the iron pan, or the galvanic
action of the zinc, quickly destroys that vessel, and the zinc contained therein
is frequently injured by being burnt. To remedy these defects, and allow of
the zincing process being carried on with greater precision and economy, I
have by my improvements cut off the connection of the fire and of the zinc
with the pan containing the zinc, by which arrangement the galvanic or electric
action hitherto so destructive to the vessel holding the fluid metal, as also to
the metal itself, is prevented, and thus the vessel will be preserved in a good
state for a much longer period.
In the accompanying Drawing, Fig. 1 is a vertical section of the apparatus
for melting zinc, and preserving it in a molten state at a uniform temperature
of about 800° Fahrenheit, to receive the articles to be coated; and Fig. 2 is a
plan or horizontal view of the same. A, A, are the walls, and B, B, the fire
bars of the furnace. C is a large cast or wrought iron pan or vessel, provided
on its upper edge with a flange, by which it is supported in the brickwork.
The bottom and sides of this pan C are surrounded by the furnace, flue or
flues, and within the pan a smaller pan D of cast or wrought iron is suspended
by a flange provided on its upper edge. A space is thus left between the sides
and bottom of the two vessels, into which space a bath composed of lead alone,
or of lead combined with tin, is placed, for the purpose of receiving the heat of
the fire, and transmitting it to the zinc. On the inner face of the pan D is
a coating of fire clay or fire brick, which is intended to prevent the action of

page_text: the zinc upon the pan D. The space between the two vessels C and D may vary
in width; but I find from experience that when the lead or tin forms a lining
of about one and a half inches in thickness between the two vessels the heat of
the fire will be readily communicated to the inner vessel, and thence to the
zinc, and this body of molten lead or tin will suffice to keep up the required
even temperarure (transmitted from the fire) to the zinc bath.
I wish it to be distinctly understood that the application of zinc to the
surface of articles constructed of metals forms no part of my Invention; but
that my improvements refer merely to the mode of preparing zinc in which
the metal articles to be coated are immersed in order to preserve them from
corrosion. I have, therefore, thought it unnecessary to describe the mode of
treating such metal articles preparatory to their receiving the coating of zinc,
such treatment being well known, and generally employed in preparing articles
for various branches of the industrial arts.
Having now described my Invention, and the manner of carrying the same
into effect, I wish it to be understood that I claim, under the above in part
recited Letters Patent, the employment of a bath of lead or tin, or any suitable
composition or medium that melts at a lower degree of heat than zinc, by
which means the heat from the fire of the furnace is taken up and transmitted
to the receptacle containing zinc, for the purpose above set forth.
In witness whereof, I, the said Andrew Smith, have hereunto set my
hand and seal, the Seventh day of August, in the year of our Lord
One thousand eight hundred and forty-six.