Burlington weekly free press. [volume] (Burlington, Vt.) 1866-1928, 1877-04-13

An important PAPER has been read before
the Society Of Arts upon n method OF pre-
serving iron from rust by coating it with its
own magnetic oxide. The facts which Pro-
lessor Barif has brought forward, and the
| specimens which he has exhibited arc such
as to Justify the belief that his discovery
will prove to lie Of enormous value, and that
it will render all kind of iron-work. how
ever much exposed /, weather or to cor
rosiye yapors or liquids, practically indie
strnctible and everlasting.
When an iron surface is exposed to the
action of water, or of moist air, it speedily
becomes covered by film Of proxtide, or
ferrous oxide, which consists of st parts by
weight of the metal to l6 oxygen. The fer
rous oxide continues to attract oxygen from
the atmosphere, and is gradually converted
into another compound, the sesquioxide, or
ierric oxide, which is composed of twice 30
parts by weight Of iron and three times
IS parts by weight Of oxygen. The lerric
oxide, in its turn, gives up some OF Its
oxygen to the as yet unOxidized iron be
meath it, and the ferrous oxide thus formed
is gradually converted into ierric oxide by
the access Of air through the spongy layer Of
superficial rust which covers it. In this
way the first formed film of rust exposes to
the atmosphere the surface which lies below
it and hence the rust becomes carrier OF
oxygen to the deeper parts of the iron, until
the latter is completely corrodcd and worn
through. Many attempts have been made
to protect iron surfaces by the application
of some kind of paint or yarnish and these
attempts have, OF course, been to some par
tial extent successful. Such cOatings, how
ever, have no real adhesion to the metal on
which they are placed, and are liable to scale
eff or perish in variety of ways. Even
when the coating is generally sound, the
smallest flaw in it, continuity will give en-
trance to the enemy; for the rust from the
exposed spot will spread laterally under the
coating, and may be all the more dangerous
and destructive from being partially con-
ccaled from view.
1t is manifested that rusting is due to the
unstable character of the two oxides men
toned, which are formed spontaneously
under ordinary climatic conditions. There
is, however, n third oxide which possesses
characteristics of totally different kind,
and which is unintluenced by moist air,
acids, and other corrosive substances. This
is the magnetic or black oxide, which con-
sists of three times Sc parts by weight Of
iron, and four times l6 parts by weight Of
oxygen. Professor BaIti has discovered that
if any iron article is exposed, at high
temperature, to the action of superheated
steam, it will become covered by Il film Of
this black oxide, of thickness which is
determined by the degree of temperature and
by the length Of exposure. The oxide is
harder than the original iron, and adheres
to it even more firmly than the particles of
iron adhere to each other, so there is a gain
not only in chemical, but also in mechanical
resistance. If the operating chamber is
heated only to 500 degrees Fahrenheit, and
the exposure is continued for only five hours,
a surface is obtained which will resist emery
paper for considerable time, and which
will not rust within doors, or after any
moderate degree of exposure to moisture.
If the Oxidizlng process is conducted at 200
degrees Fahrenheit, and continued for six or
seven hours, the surface will resist 4 rasp,
and will bear any amount Of exposure to
weather. The oxidation does not affect the
appearance Of the surface in any other way
than by tuihii.g it black. a rough iorg-
Ing retains It's rOughness, and turned or
polished surface retains its smoothness. If
there should be any flaw in the coating, Or
if the black oxide is designedly removed
from part of the surface, the common oxida-
tiOn will occur where the iron is thus left
unprotected But such oxidation is strictly
limited to the unprotected portion, and has
not the smallest tendency either to spread
laterally under the black oxide or TO dctach
this from the suhjrcent parts.
Among tho most valuable and impoi tant
of tie probable applications of the invention
will be the protection Of steam boilers
and of the plates of iron ships; and Profess
sor BaIli hopes that it will be possible to op-
crate upon very large manufactured articles
without its being necessary to provide heat
ing chamber large enough to contain them.
The applications seem almost without num-
Der. The process will be conducted at very
small cost, and twill probably be employed,
at no distant time, for iron goods OF every
description. Copper vessels will no longer
possess any advantages for cooking, and iron
saucepans will no longer need to be tinnel.
Lcaden pipes for the conveyance of water
will in all probability be entirely superseded
and there can be no doubt that new uses for
incorrodiblc iron will every day suggest
themselves