Improvements relating to the Galvanizing of Metals and to Apparatus therefor.
Year: 1889

page_text: Date of Application, 17th May, 1889-Accepted, 29th June, 1889
COMPLETE SPECIFICATION.
Improvements relating to the Galvanizing of Metals and to
Apparatus therefor.
We, THOMAS MIDGLEY, of Beaver Falls in the county of Beaver, and State of
Pennsylvania, United States of America, Mechanic, and WALTER BRIGHAM NYE, of
Boston, in the county of Suffolk, and State of Massachusetts, United States of
America, 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 :-
This invention relates to the galvanizing of metals in different forms such as wire,
rods, strips, sheets, pipes and the like. There are various disadvantages attending
the use of processes of galvanizing heretofore practiced either or all of which result
in large loss not only on account of injury caused to the material itself, but also
because of the necessity of frequently repairing or replacing the pan which contains
the bath. In the first place the quality of the material is lessened when the zinc is
deposited directly upon it, it being a well-known fact that the effect of zinc upon iron
is to harden and give it a certain amount of temper which is a disadvantage when
flexibility is required, as in the case of galvanized wire. It is also well known
that zinc in a melted state is extremely susceptible to oxidation, and as the bath
ordinarily used has a large surface exposed to the air the loss on this account is
considerable. There is also a certain percentage of loss occasioned by the chemical
action of the acids generally used upon the zinc bath. The most important dis-
advantage however in the use of the bath as ordinarily constructed results from the
destruction of the pans which contain the zinc, caused by the extreme affinity between
the zinc bath and the iron of which the pan is composed, which results in the formation
of dross, and this loss in large establishments reaches very large proportions, not only
from the expense of renewing the pans but on account of frequent stoppage of
operations for the purpose. The object of our invention is to overcome all these dis-
advantages and thus produce a better quality of galvanized material by a much more
economical process of manufacture.
Our process consists, first, in immersing the material after it has been treated with
acid in the usual manner in a bath of molten lead, and then in passing it through a
small body of melted zinc which floats upon the surface of the lead, being suitably
confined to prevent it from spreading over the surface of the lead bath. By thus
confining the zine within a small space upon the surface of the lead any material to
be treated passes first into and through the lead and thence directly through and
out of the zinc bath from which it receives the final coating. By this arrangement
of the apparatus the surface of zinc exposed to the air is very small and the amount
of oxidation correspondingly reduced. The injurious effects of the acid upon zinc is
also entirely obviated, since they are not brought in contact. Another important
advantage arising from the use of this process is that the wire or other material in
its passage through the lead is heated to a temperature nearly if not quite up to that
of the zinc, and thus the hardening effect of zinc in a molten state upon metal at a
normal temperature is entirely prevented. This heating of the material also tends to
prevent the formation of dross.ordinarily caused by the great difference in temperature
between the bath and the material-exposed to it. By using the small body of zinc
and restraining it in place by movable partitions the loss resulting from the affinity
of zinc with the iron of the pan itself is also completely prevented, this action being
estricted to the partitions themselves which are easily removed and replaced at any
ime and at a small cost.

page_text: We have devised an apparatus for carrying out our process, which is illustrated
in the accompanying drawings in which
"
Figure 1 is a longitudinal section on the line a, a of Figure 2.
Figure 2 is a plan view; and
Figure 3 is a cross section on the line y, y of figure 2.
A represents the large iron lined pan which contains a bath of molten lead kept
in that condition by the application of heat in any suitable manner. B represents
the zinc bath which is formed by means of walls D D. This bath has an open
bottom which permits the lead to enter it to a certain height as shown. It will be
understood that the walls composing the zinc bath may be located at any point relative
to the pan A, their position being governed by the nature and the shape of the material
under treatment. We have shown them in the drawing as supported at the exit end
of the lead bath when used for galvanizing wire. Within these retaining walls is
confined a body of molten zinc which by reason of its smaller specific gravity floats
upon the surface of the lead in the pan A. E represents the acid bath and a a
designate rollers by means of which the strands of wire are fed and guided passing
from the acid bath directly into and through the molten lead, and being carried thence
directly through the body of, zinc as shown. F represents a cover over the zinc
bath, and Ga chamber into which the products of combustion pass from a fire
box H through cover F out of pipe shown in drawing. Passages K extend along
the sides of the pan A and are provided with ash-pits L beneath them. Both pans
are thus heated and their temperature maintained at the same time.
Having now particularly described and ascertained the nature of our inven
tion and in what manner the same is to be performed, we declare that what we
claim is
First. The above described process of galvanizing metal which consists in passing
the metal into and through a large body of lead, and through and out of a smaller
body of zinc floating upon the lead, as herein described and for the purpose set
forth.
Second. The above described galvanizing apparatus which consists of a large pan
for holding the lead, and means for heating the same, and a smaller open bottom pan
for confining the zinc upon the surface of the lead, and means for heating the same,
as, and for the purpose described.
enteenth day or may 1007.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, Agents for the Applicant.