Improvements in the Manufacture of Galvanized Iron.
Year: 1891

page_text: COMPLETE SPECIFICATION.
Improvements in the Manufacture of Galvanized Iron.
I, JOSEPH WILLIAM RICHARDS, of No. 1802 Catharine Street, in the City of
Philadelphia and State of Pennsylania, United States of America, Metallurgical
Chemist, do hereby declare the nature of this invention and in what manner the
same is to be performed, to be particularly described and ascertained in and by the
following statement :—
My improvements relate to the process of coating iron with zinc in the manner
which is commercially called "galvanizing," and they embrace also the product of
said process.
As is well known, the ordinary method of "galvanizing" sheet or other iron
consists in dipping it into a hath of melted zinc and allowing it to remain until a
layer of zinc of the desired thickness has been deposited thereon and adheres
thereto.
I have discovered that by the diffusion of a very small percentage of metallic
aluminum throughout the bath of melted zinc, a much more uniform deposit upon
the sheet of iron can be effected, and, moreover, that, as compared with previously
known products, the coating is highly crystalline and permanently brilliant, while
at the same time being exceedingly malleable and tenacious as well as strongly
adherent to the iron.
For the conduct of my process in its preferred form, I proceed as follows:
As the quantity of aluminum required is very small, its diffusion throughout a
large bath might be found practically difficult, were it used alone, or in a pure
form.
1, therefore, first form an alumino-zinc alloy by melting in a suitable crucible,
say, two per cent. of metallic aluminum and adding thereto ninety-eight per cent. of
metallic zinc. When thoroughly combined, the alloy thus formed is cast into small
bars for convenience in use. The zinc in this alloy is, however, merely a vehicle
for the aluminum contained therein to permit its more ready diffusion throughout
the galvanizing bath, and said alloy is not to be understood as being a product of
my process, nor is its use essential to the same.
Having prepared the "galvanizing "bath in the usual manner by melting a
sufficient quantity of zinc, I add the alumino-zinc alloy, just described, thereto,
preferably in the quantity of about four ounces of alloy to the ton of melted zinc in
the bath, and after allowing a few minutes for diffusion of aluminum throughout
the bath, I dip the sheet or other iron which is to be "galvanized" in the ordinary
manner.
As the bath is depleted, and new additions of zinc are made thereto, the alumino-
zinc alloy should be added in the same proportions as before.
I find that the crystalline formation of the deposited zinc varies with the amount
of aluminum in the bath, the size of said crystals increasing (up to a certain limit)
with the increased percentage of aluminum, but irrespective of the differences in
degree which results from the use of a greater or less percentage of aluminum, the
advantageous qualities above described as incident to such use, will result from the
conduct of the “galvanizing” process in the presence of aluminum in any substantial
quantity. Hence I do not limit my claim to the use of the above-mentioned
proportions.
As above stated, I do not claim the alumino-zinc alloy, as such, nor does my
claim necessarily involve the presence of alloyed or free aluminum, recognizable as
such, in the coating which is deposited upon the iron, though doubtless the use of a
very much larger percentage of aluminum than is commercially desirable at the

page_text: present prices might be found to be productive of good results, independent of the
peculiar effect of the "galvanizing” process.
It must be understood that my invention does not necessarily involve the deposit
of an alumino-zinc alloy recognizable as such in the final product, and I do not wish
to be understood as limiting myself to a process which yields such an alloyed
coating. Hence in using the words "alumino galvanizing" as a convenient term to
describe the process, I do not intend that the coating must essentially be a recog-
nizable alloy, but merely that it possesses the characteristics due to deposit in the
presence of aluminum.
Furthermore, though I have described the use of a vehicle, or primary alloy of
aluminum and zinc, as the best method known to me of diffusing the aluminum
throughout the "galvanizing" bath, I do not mean to restrict my claim to the use
of a vehicle for this purpose, since any method of addition which effectually diffuses
the metallic aluminum throughout the bath, would be the equivalent of the described
process.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is:
1. The hereinbefore described process of alumino-galvanizing iron which consists
in diffusing metallic aluminum throughout a bath of metallic zinc, and then dipping
the iron in said composite bath, and permitting the coating to deposit thereon,
substantially as set forth.
2. As a new manufacture an alumino galvanized iron having a highly crystalline,
permanently brilliant and adhesive coating of zinc, substantially as set forth.
Dated this 25th day of June in the year 1891.
JOSEPH WILLIAM RICHARDS.