Steel Suriaces and Protecting them from Rust.
Year: 1887

page_text: Date of Application, 16th June, 1887.
Specification Accepted, 26th July, 1887.
Steel Suriaces and Protecting them from Rust.
I, JAMES YATE JOHNSON of 47 Lincolns Inn Fields in the County of Middlesex
Gentleman 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 :-
The principal object of this Invention is to render the surfaces of articles made of
steel or wrought or cast iron inoxidable by means of electricity as hereinafter
described.
The browning processes heretofore employed in finishing sporting and other gun
barrels for example are tedious and costly and consist in fact in merely coloring the
metal. The surface is first oxidized by artificial means such as the application of
various chemical solutions which either attack the surface or deposit alloys or
amalgams thereon or in some cases as in heating military guns for example superheated
steam is employed which converts the sesqui oxide of iron Fe³ O³ into black magnetic
oxide Fe³ 04.
According to the present Invention a similar effect is produced by simply subjecting
the metal to the action of an electric current as hereinafter set forth in a bath of
distilled water or ordinary water preferably heated to from about sixty to seventy
degrees Centigrade.
In treating an article of iron or steel according to this invention the surface of
the metal is first oxidised by means of a bath of very slightly acidulated water or of
water mixed with a very small quantity of perchloride of iron and hydrochlorate of
ammonia. When the surface is uniformly coated with a layer of oxide Fe² 0³ the
article being placed in a water bath heated as aforesaid is connected with the
positive pole of a suitable generator of electricity the negative pole being connected
with any suitable electrode of metal or carbon. A current of from about two to
three rolls and a number of ampéres in proportion to the area of surface to be treated
is then caused to pass through the combination. A layer of black oxide Fe 0₁ is

page_text: immediately formed upon the iron or steel at the positive pole or electrode. When
this layer is spread accurately and equally over the entire surface of the article (which
usually requires from about twenty to twenty five minutes) the article is removed from
the bath and dried. The article being warm dries very rapidly and on being brushed
with a common brush the coating of oxide acquires a high polish. In case the
coating of magnetic oxide thus produced appears too thin the preliminary oxidizing
treatment may be repeated so as to coat the article a second time with a layer of
oxide Fe² O after which the article is replaced in the bath of hot or warm water
and acted on by the electric current as before. After two such operations the surface
usually acquires a brilliant ebony blackness and resists the action of the hardest
scratch brush.
An apparatus which may be employed in carrying out this invention is illustrated
in longitudinal vertical section and in plan respectively in Figures 1 and 2 of the
accompanying drawings.
In this apparatus an iron trough A B C D is divided into a suitable number of
compartments by iron partitions f. The edges of the trough are covered by a
frame a b c d of wood or other insulating material.
This frame is provided with copper bars or rods t extending transversely over each
compartment and serving as supports from which the articles to be treated can be
suspended in the hath by means of wire or other conductors s.
The transverse bars t are connected together by Conductors m. The positive
conducting wire or pole of the current is connected through the said transverse bars
with the iron or steel articles formning the positive electrodes the negative wire being
connected with the negative electrode which is formed by the trough itself.
The bath of distilled or other water in the trough is heated to preferably from about
sixty to seventy degrees Centigrade as aforesaid but the temperature may be raised
to one hundred degrees if required. The heat renders the water a better conductor
and by expanding the metal enables it to be more uniformly acted upon.
A small quantity of proto-chloride of Iron or of hydrochloric Acid may be added to
the liquid H.O. This causes the oxidation to proceed more rapidly but the
Oxide Fe³ O is less homogeneous or solid being mixed with Chloride of Iron.
It will be observed that in this process the action is the reverse of what takes place
in ordinary electro deposition processes a combination being formed at the positive
clectrode in place of a deposit at the negative electrode.
It is evident that the Oxide Fe³ 0+ formed under the conditions hereinbefore set forth
is more firmly united to the metal and is more strongly rooted in position than by
any process heretofore employed. Moreover the operation is much less complicated
requires less labour and is more economical than the ordinary treatment.
Cold water may be employed in place of the hot or warm water hereinbefore
referred to but in this case the operation requires more time and the electro motive
force of the current requires to be increased.
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 :-
Browning or coloring iron or steel surfaces and protecting them from rust by the
application of an electric current in the presence of water heated or otherwise in such
a manner as to form a strongly adhering coating of magnetic oxide upon the surface
of the metal substantially as hereinbefore described.
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