Improvements in the Pickling and Scrubbing of Iron and Steel Slabs, Plates, Wire Coils, and other Articles, and Apparatus for that Purpose.
Year: 1893

page_text: Date of Application, 5th Jan., 1893
Complete Specification Left, 21st Sept., 1893-Accepted, 30th Dec., 1893
PROVISIONAL SPECIFICATION.
Improvements in the Pickling and Scrubbing of Iron and Steel
Slabs, Plates, Wire Coils, and other Articles, and Apparatus for
that Purpose.
We, WILLIAM STEPNEY RAWSON, Electrical Engineer and WOODHOUSE
& RAWSON UNITED LD. Electrical Contractors and Engineers, both of
88 Queen Victoria Street E.C. do hereby declare the nature of this invention to
be as follows:-
:―
Our invention relates to processes and apparatus for the pickling and scrubbing
of articles in iron and steel, such as slabs, plates, coils of wire &c., so as to prepare
them for being coated with tin or other metal, the chief objects which we have in
view being to economise the time, labour and acid required for these operations
and to avoid corrosion of the metal. As the process of pickling and scrubbing is
applied to plates which are to be tinned to a larger extent than to any other iron
or steel articles, we may best illustrate our invention by describing our process as
applied to such plates.
For what is known as black pickling we place a number of plates parallel or
nearly so and near together, but without touching each other, in a tank containing
dilute acid such as hydrochloric or sulphuric acid, and we connect the plate at the
one end of the row with one terminal, say the + of a dynamo machine or other
source of electricity, and the plate at the other end of the row with the other
or -
terminal.
We pass a current of electricity for some time through the liquid and plates, and
then, by means of a suitable switch or commutator, we reverse the direction of the
current for a time. After several alternations of current, the scale is loosened from
the surface of the plates and finally drops or is brushed off, the plates being thus
pickled and scrubbed. In some cases, we place at intervals in the tank in the
places of some of the metal plates, plates of carbon which may be made up of
comparatively small pieces of carbon fixed in wooden frames like the panes of glass
in a window. The switch or commutator for effecting reversals of current may be
worked by clockwork or equivalent motor timed to periods suitable for reversal.
The action is promoted by a little elevation of the temperature of the bath, say
from 70° to 90° F.
For white pickling, we place the metal plates each against a carbon plate
holding it in a suitable frame by which it is in electric connection with the carbon.
All the plates in the tank are placed so as to face one way. After passing the
electric current for a time from the + terminal to the first carbon and to
the terminal from the last plate, the set of carbon and metal plates have become
somewhat in the condition of a storage battery, so that if the current is to be
reversed, only a portion of the electro motive force from the generator is required,
the contents of the tank contributing the rest as a secondary battery. The con-
ductors for the generator current may therefore, for reversal, be disconnected and
the range of plates short circuited by connecting the first plate to the last, inter-
posing if necessary a suitable resistance. In both the black and the white pickling
processes, the electric leads may be permanently connected to plates of carbon or
iron fixed at the ends of the tank.
For convenience of charging the tank with plates to be operated on and
discharging them, we prefer to provide suitable frames, crates or boxes, which may
be of wood, to be lowered into the tank charged with plates held in lateral grooves
or between pegs projecting from the bottom or sides, the plates being thus held
separate from each other, like the slices in a toast rack. We provide also an

page_text: upright column with an arm that can swing round like the jib of a crane and a
winch or other suitable gear for raising and lowering the frames containing the
plates. In one position, the jib stands over a platform on which a frame rests
while the plates are put into it or taken from it. In a second position the jib
stands over the pickling tank to lower the frame of fresh plates into it or to raise
the frame of pickled plates. In a third position the jib stands over a water tank
in which the pickled plates are washed. There may be more than one platform,
pickling tank and washing tank, commanded by the one cranc.
The process above described as applied to plates is conducted in a similar manner
for the treatment of slabs, coils or banks of wire and other articles, the boxes,
frames or crates being suitably arranged for holding them in the tanks.
Dated this 5th day of January 1893.
ABEL & IMRAY,
Agents for the Applicants.
COMPLETE SPECIFICATION.
Improvements in the Pickling and Scrubbing of Iron and Steel
Slabs, Plates, Wire Coils, and other Articles, and Apparatus for
that Purpose.
We, WILLIAM STEPNEY RAWSON, Electrical Engineer, and WOODHOUSE &
RAWSON UNITED LD. Electrical Contractors and Engineers, both of 88 Queen
Victoria Street E.C. 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:—
Our invention relates to processes and apparatus for the pickling and scrubbing
of articles in iron and steel, such as slabs, plates, coils of wire &c. so as to
prepare them for being coated with tin or other metal, the chief objects' which
we have in view being to economise the time, labour and acid required for these
operations and to avoid corrosion of the metal.
As the process of pickling and scrubbing is applied to plates which are to be
tinned to a larger extent than to any other iron or steel articles, we may best
illustrate our invention by describing our process as applied to such plates.
For what is known as black pickling we place a number of plates parallel or
nearly so and near together but without touching each other in a tank containing
dilute acid such as hydrochloric or sulphuric acid, and we connect the plate at
the one end of the row with one terminal say the + of a dynamo machine or
other source of electricity, and the plate at the other end of the row with the
other or terminal.
-
We usually employ about 6 per cent. of hydrochloric acid of specific gravity 1.140
or about 3 per cent. of sulphuric acid of specific gravity 1.750, but smaller per-
centages may be employed."
We pass a current of electricity for some time through the liquid and plates,
and then by means of a suitable switch or commutator we reverse the direction
of the current for a time.
We usually reverse about 4 times per minute, but with deep plates reversals
should be less frequent so as to give time for the hydrogen bubbles to sweep
up the plate from the bottom where the scrubbing action begins.
After several alternations of current during about 10 minutes when the acid
is of the strength mentioned above, the scale is loosened from the surface of the
plates and finally drops or is brushed off, the plates being thus pickled and
scrubbed. After the scale is off, there is no farther action at the negative pole
on the clean metal unless the acid is strong.
In some cases we place at intervals in the tank in the place of some of the
metal plates, plates of carbon which may be made up of comparatively small
pieces of carbon fixed in wooden frames like the panes of glass in a window.
The switch or commutator for effecting reversals of current may be worked by

page_text: clockwork or equivalent motor timed to periods suitable for reversal.
The action
is promoted by a little elevation of the temperature of the bath, say. from 70° to
90° F. or higher when the acid is weak..
For white pickling we place the metal plates each against a carbon plate
holding it in a suitable frame by which it is in electric connection with the
carbon. All the plates in the tank are placed so as to face one way. After
passing the electric current for a time from the + terminal to the first carbon
and to the terminal from the last plate, the set of carbon and metal plates
have become somewhat in the condition of a storage battery so that if the
current is to be reversed, only a portion of the electro motive force from the
generator is required the contents of the tank contributing the rest as a secondary
battery. The conductors for the generator current may therefore for reversal
be disconnected and the range of plates short circuited by connecting the first
plate to the last, interposing if necessary a suitable resistance.
In both the black and the white pickling processes, the electric leads may be
permanently connected to plates of carbon or iron fixed at the ends of the tank.
When sulphuric acid is employed lead plates may be used for this purpose; when
hydrochloric acid is employed, iron plates may be used and these may be protected
against dissolution by placing plates that are to be pickled in close contact with
them.
In all cases care should be taken not to work with liquid too rich in salts of iron
as there might be deposit which would interfere with the pickling action. The
proportion of iron salts should not exceed 15 per cent. by weight.
For convenience of charging the tank with plates to be operated on and discharging
then we prefer to provide suitable frames, crates or boxes which may be of wood to
be lowered into the tank, charged with plates held in lateral grooves or between pegs
projecting from the bottom or sides the plates being thus held separate from each
other, like the slices in a toast rack. We provide also an upright column with an
arm that can swing round like the jib of a crane and a winch or other suitable gear
for raising and lowering the frame containing the plates. In one position, the jib
stands over a platform on which a frame rests while the plates are put into it or
taken from it. In a second position the jib stands over the pickling tank to lower
the frame of fresh plates into it or to raise the frame of pickled plates. In a third
position the jib stands over a water tank in which the pickled plates are washed.
There may be more than one platform pickling tank and washing tank commanded
by the one crane.
The process above described as applied to plates is conducted in a similar manner
for the treatment of slabs, coils or hanks of wire and other articles, the boxes frames
or crates being suitably arranged for holding them in the tanks.
A number of wires may be drawn slowly through the tank side by side but not
touching each other the two outer wires being connected to the electric generator
and having the current reversed from time to time.
The white pickling process above described may be applied for cleaning brazed
joints of iron or steel.
For this purpose the article may be immersed in a lead lined tank containing
from 1 to 2 per cent. by bulk of sulphuric acid. One terminal of the electric
generator is connected to the immersed article, the other to the lead lining, and the
current being occasionally reversed, but preferably the article should be in the
condition of cathode 3 or 4 times as long as it is anode.
Sometimes plates are clean on their one side. In such case we put two of them
with their clean sides close together so as to form as it were a single plate, very
little action on the clean sides taking place.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, we declare that what we
claim is :-
1. The herein described process for pickling and scrubbing iron or steel articles

page_text: by subjecting them in dilute acid to the action of an electric current from time to
time reversed.
2. For effecting the process above referred to apparatus consisting of pickling
tanks, conductors and an electric generator in combination with a reversing switch
or commutator moved at suitable intervals by clockwork or other suitable motor,
substantially as described.
Dated this 21st day of September 1893.
ABEL & IMRAY,
Agents for the Applicants.