A well-informed correspondent, Samuel Crowther, of The New York Tribune,
lately returned from Germany, observed a method of plating metals, in
which comprest air was employed. This machine for plating, the
correspondent declares, is very highly regarded by the Germans. The
surface to be plated is cleaned with chemicals and then a thin sheet of
the plating metal is blown on with a device resembling a hand torch. The
torch contains a small electric furnace which reduces the plating metal
to a liquid and thru the connection with a tank of comprest air the
molten metal is sprayed onto the surface. See accompanying sketch.
By this method, gun metal, brass and copper were put on iron or steel for
such parts of machines as required it, the coated metal parts being used
instead of solid gun metal, brass and copper. This saved large quantities
of these three products when they were exceedingly scarce in Germany.
This particular comprest air and electric furnace plating scheme is
portable and declared to be most convenient in usage. It is expected by
the Germans to have a permanent and wide use in the coating of ships’
bottoms, tanks and other large structures where the plates cannot be
plated before erection. In fact, Mr. Crowther reports, it constitutes a
new variety of metal painting arrangement.
The well-known Schoop process is said to be about eight years old and is
capable of depositing lead, tin, zinc, aluminum, copper, nickel and their
alloys on any coherent object, whether metallic or not. The thickness of
the coating is under instant control and the application can be limited
to any portion of the object.
The difference between the original Schoop method and that described by
Mr. Crowther is that the former involved the use of a "pistol," air at 40
lbs. pressure, a tank of hydrogen and another tank containing some
reducing gas, usually oxygen, acetylene or blau-gas, the metal to be
applied being liquefied in flame; whereas in the latter a small electric
furnace is utilized to make the metal molten before it is projected by
the air pressure. The Schoop process has been used in the United States
to some extent, but is still susceptible of considerable development.
Here its use is said to have been wholly for its convenience in ordinary
practice and not as an economical expedient.
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