Improvements relating to the Pickling of Metals and Alloys to Remove Oxide and other Impurities from the Surface thereof.
Year: 1893

page_text: Date of Application, 22nd Mar., 1893
Complete Specification Left, 22nd Dec., 1893-Accepted, 22nd Mar., 1894
PROVISIONAL SPECIFICATION.
Improvements relating to the Pickling of Metals and Alloys to
Remove Oxide and other Impurities from the Surface thereof.
I, ARTHUR JAMES SMITH, of Kingston-on-Thames, in the County of Surrey,
Chemist, do hereby declare the nature of this invention to be as follows:-
My invention relates to the pickling of metals and alloys for the purpose of
removing oxide and other impurities from the surface thereof, to clean the same or
to prepare the said surface for coating, with other metals, or for wire-drawing,
rolling, hammering or other treatment.
The pickling of metals or alloys is usually effected by immersing the metal
sheets or other articles in acid solutions for a longer or shorter period according
to the strength of the acid solution and the character of the article under
treatment. The chemical action set up in this process causes the evolution of
hydrogen gases and other compounds, thus producing an offensive odour. Moreover
pitting or pocking of the sheets or other articles frequently takes place, chiefly
by reason of local electrical action. And, after the pickling, there are usually
found on the surface of the metal, portious which have not been properly acted
upon by the acid solution, which portions require to be scoured, scraped or otherwise
treated.
Now my invention is designed to obviate these defects and inconveniences, to
improve the quality and reduce the cost of manufacture of the articles, and at the
same time to expedite the process and utilize the chemical and electrical energy
that is capable of being developed in the pickling-vats, for the production of
electric currents, which can either be used directly, or stored for subsequent use
for electric ligbting or for other purposes.
I have found that, by converting the pickling-vats into battery-cells in which
the metallic articles serve as the positive plate or element, not only do I obtain a
large amount of electrical energy, but the pickling is performed more uniformly,
effectively and expeditiously than heretofore. Moreover, by the addition of
suitable substances to the acid bath, I can increase the potential of the electrical
energy generated by the pickling process, and at the same time obviate the
disagreeable smell that usually accompanies the pickling.
My improved process of pickling, therefore, is carried into effect as follows, vi:.:-
I insert in each pickling-vat, one or more negative plates or elements, of carbon or
other suitable material, and 1 connect the said plates or elements with one conductor
of an external circuit in which are included one or more suitable electric lamps, or
other apparatus for the utilization of the electrical energy, or one or more secondary
batteries or accumulators for storing such energy. Moreover I connect the article
or articles to be pickled in the said vat, with the other conductor of the said external
circuit.
I find it advantageous to connect a large number of vats thus converted into
battery cells, with suitable distributing-mains for either quantity (ampères) or
tension (volts) by series. In making new vats for pickling sheets of metal or other
articles, it is desirable to arrange, in each vat, as large a surface as practicable
of negative plate or element, preferably surrounding the metal to be pickled, and
suitably connected with the external circuit, and to provide the vat with one or
more metallic supports for the said sheets or other articles, which support or
supports are also suitably connected with the said external circuit.
I find it advantageous to employ as the negative plate or element, either carbon,
or wire gauze electroplated with silver in a crystalline state. Moreover I prefer

page_text: to platinize the said carbon or wire-gauze by dipping it in a solution of bi-chloride
of platinum and reducing the platinum to the black amorphous condition within
the pores of the carbon, by heating it in a hydrogen flame. I sometimes use
copper-wire gauze electroplated with reguline silver to protect it against the acid,
and having a deposit of crystalline silver on the first covering of silver to increase
the active surface for the platinum black. I can, however, use other suitable
materials as the negative plate or element.
I can, if desired, use the ordinary bath of dilute sulphuric or other acid as the
electrolyte. I find it more advantageous, however, to add to the sulphuric or other
acid solution a suitable depolarizer, preferably chromic acid, as I am thus enabled
to obtain an increased potential of the electrical energy and at the same time greatly
expedite the pickling process, and avoid the offensive smell that usually arises
therefrom. I add this depolarizer to the acid solution until I observe the hydrogen
'cease to be evolved. In some instances, I add to the electrolyte a small quantity
of chlorate of potash or equivalent substance to further increase the electromotive
force generated.
I find that articles of iron pickled by my improved process, after being dipped
in a solution of ammonium-chloride and zinc, take the tin, zinc or lead very evenly
and efficiently, and that but little if any pitting or pocking of the surface of the
iron takes place. Moreover the surface of the pickled articles is more free from
the detriments usually found on iron pickled in the manner heretofore practised.
A further advantage afforded by my invention is that it enables me as above
mentioned to entirely obviate the nuisance that arises from the offensive effluvia
produced by the ordinary pickling process.
I can, if desired, use a nitrate, such as nitrate of soda, or other suitable
depolarizer; I find, however, that I obtain better results with chromic acid.
It is evident that my invention is applicable for the pickling of metal articles to
prepare the same for treatment in various ways, such, for example, as tiuning or
zincing, or simply for the purpose of cleaning such articles. The pickling of iron
preparatory to coating the same with tin, zinc or lead can be very conveniently
and advantageously effected by my improved process, especially when chromic acid
is mixed with the sulphuric acid solution, and the negative plates or elements used
are of carbon or of wire-gauze prepared as above mentioned.
Dated the 22nd March 1893.
D. YOUNG & Co.,
11 & 12, Southampton Buildings, London, W.C.,
Agents for the Applicant.
COMPLETE SPECIFICATION.
Inprovements relating to the Pickling of Metals and Alloys to
Remove Oxide and other Impurities from the Surface thereof.
I, ARTHUR JAMES SMITH, of Kingston-on-Thames, in the County of Surrey,
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 :-
My invention relates to the pickling of metals and alloys for the purpose of
removing oxide and other impurities from the surface thereof, to clean the same or
to prepare the said surface for coating with other metals or for wire-drawing,
rolling, hammering or other treatment.
The pickling of metals or alloys is usually effected by immersing the metal.sheets
or other articles in acid solutions for a longer or shorter period according to the
strength of the acid solution and the character of the article under treatment.
The chemical action set up in this process causes the evolution of hydrogen and
other compounds, thus causing offensive and noxious effluvia. Moreover, pitting

page_text: or pocking of the sheets or other articles frequently takes place, chiefly by reason
of local electrical action. And, after the pickling, there are usually found portions
of the surface of the metal which have not been properly acted upon by the acid.
solution, which portions require to be scoured, scraped or otherwise treated.
Now my invention is designed to obviate these defects and inconveniences, to
improve the quality of the pickled articles, and at the same time to expedite the
process, and to utilize the chemical and electrical energy that is capable of being
developed in the pickling-vats for the production of electric currents, which can
either be used directly or stored for subsequent use for electric lighting or for other
purposes.
I have found that, by converting the pickling-vats into battery-cells in which
the metal articles to be pickled serve as the positive plate or element, so that
electricity is generated simultaneously with the pickling of the said articles, not
only am I enabled to obtain a large amount of electrical energy, but the pickling
is performed more uniformly, effectively and expeditiously than heretofore. And,
by the addition of suitable substances to the acid bath, I can increase the electrical
energy developed in the pickling process, and at the same time obviate the
disagreeable smell that usually accompanies the pickling.
My improved process of pickling, therefore, is carried into effect as follows,
viz. I immerse in the solution in each pickling-vat one or more negative plates or
elements of carbon or other suitable material, and I connect the said plates or
elements with one of the poles or terminals of au external circuit in which are
included one or more suitable electric lamps, or other apparatus for the utilization
of the electrical energy, or one or more secondary batteries or accumulators for
storing such energy. The article or articles to be pickled in the said vat, I connect
with the other pole or terminal of the said external circuit, so that they will serve
as the positive plate or element of the primary battery thus constituted.
I find it advantageous to connect a large number of vats thus converted into
battery-cells, with suitable distributing mains for either quantity or tension. In
making new vats for pickling sheets of metal or other articles, it is desirable to
arrange in each vat, as large a surface as practicable of negative plate or element,
preferably surrounding the metal to be pickled, and suitably connected with the
external circuit, and to provide the vat with one or more metallic supports for the
sheets or other articles to be pickled, the said support or supports being also
suitably connected with the external circuit.
Before withdrawing from either vat, a sheet or other article the pickling of
which has been completed, a fresh sheet or other article to be pickled should be
inserted in the said vat, so as to avoid any sudden variation or interruption of the
current.
I find it most advantageous to employ as the negative plate or element, either
carbon, or wire-gauze electroplated with silver. Moreover I prefer to impregnate
the said carbon, or cover the said wire-gauze with amorphous platinum black, by
dipping the said carbon or plated wire-gauze in a solution of bi-chloride of platinum
and depositing the platinum in the black amorphous condition within the pores of
the carbon, or upon the gauze, by heating the carbon or gauze thus treated, in a
flame of hydrogen.
In treating carbon for this purpose, I prefer to employ a weak solution of
platinum bi-chloride, as I find that, within a certain limit, the action is better the
more attenuated the solution in which the carbon is soaked before being submitted
to the hydrogen flame.
If the quantity of amorphous platinum black thus applied, is not considered
sufficient, it is better to again dip the carbon in the weak solution and subject it to
the action of the hydrogen flame, than to employ in the first instance a more
concentrated solution of platinum bi-chloride, as the weak solution can more easily
enter the pores of the carbon.
When I use carbon for the negative element, I sometimes make.the said element
of strips or rods of carbon arranged in the form of a grid or grating and

page_text: suitably connected with each other and with the external circuit. I thus provide
an element which, in proportion to the space it occupies, has a large area of active
surface in contact with the electrolyte, thereby diminishing the internal resistance
of the cell.
.
When I employ a nitrate depolarizer as hereinafter described, I sometimes use
copper wire-gauze electroplated with reguline silver to protect it against the
sulphuric acid, and having a deposit of crystalline silver on the first covering of
silver, to increase the active surface for the platinum black.
It is obvious, however, that I can, if desired, use other suitable materials as the
negative plate or element.
In the pickling of iron, I can, if desired, employ the usual bath of dilute
sulphuric acid. I find it more advantageous, however, to add to the sulphuric acid
solution, a suitable depolarizer, preferably chromic acid, as I thus increase the electrical
energy developed, and at the same time greatly expedite the pickling process,
and avoid the offensive smell that usually arises therefrom. For this purpose,
it is best to add, at starting, say five per cent., more or less, of chromic acid;
and a further quantity of this depolarizer should, from time to time, be added as
may be found necessary, to prevent the evolution of hydrogen and maintain the
electrical energy.
I. sometimes use a nitrate, such, for instance, as nitrate of soda, as the
depolarizer; I find, however, that I obtain better results, in the pickling of iron,
by the use of chromic acid.
With some metals or alloys, it may be found necessary or desirable to use other
depolarizers, or to use the pickling solution without a depolarizer.
By the employment of chromic acid in an electrolyte consisting of dilute
sulphuric acid, in which are immersed a positive element of iron and a negative
element of amorphous platinized carbou made in the form of a grid or grating, I
am enabled to obtain such good results in respect of the electrical energy.
developed, that a battery thus formed can be advantageously used to generate
electricity without utilizing the pickling action, the iron being used simply to
serve as the positive element, and being cheaper than the zinc usually employed in
chromic acid cells.
In the accompanying drawing I have shown how my invention may be con-
veniently and advantageously carried into practice for the pickling of iron articles
of various kinds.
A is the pickling-vat which may be of the usual or other suitable construction.
B, B are rods resting upon the upper edges of the ends of the said vat for the
purpose of supporting the articles to be pickled so that they are suspended in the
pickling solution. The negative element is composed of a large number of
sticks C of carbon prepared or treated in the manner above described and
threaded upon rods D which also rest upon the upper edges of the ends of the
vat A. Washers c of copper or other suitable material are placed on the rods D
between the pieces C of carbon and the said washers and the pieces of carbon are
firmly held in place upon the rods D by means of nuts d screwed upon the said
rods. A grid of carbon is thus provided at each side of the interior of the rat A.
The rods B and D preferably consist of copper tubes having iron cores. To the
rods D are secured the binding posts a to which is connected the negative
conductor a¹ of the external circuit; and to the rods B are secured the binding
posts to which is connected the positive conductor 6' of the external circuit.
The said conductors a', b' are preferably formed of copper ribbon. The articles to
be pickled, some of which are shown at e, f, and g, are suspended from the rods B
by means of metal hooks or other suitable devices.
I find that articles of iron pickled by my improved process, after being dipped
in a solution of ammonium chloride and zinc, take either tin, zinc or lead very
evenly and efficiently, the surface of the iron or other metal being more porous or
spongy, so that (in rough or unplanished work) the molten metal will adhere
more firmly to the iron than heretofore. I find, moreover, that but little if any

page_text: pitting or pocking of the surface of the iron takes place, and the surface of the
pickled articles is more free from the detriments usually found on iron pickled in
the manner heretofore practised.
Another important advantage afforded by my invention is, that it enables me to
pickle metal articles of various kinds more efficiently than is practicable by the
process hitherto employed. I can, for example, very advantageously treat, by
my improved process, very thin metal goods, such as very thin sheet-metal or
very fine wire, so that the same can be coated with tin, zinc or other metals, as I
am enabled to control or adjust the biting power of the pickle by using a very
weak acid solution to which is added a small percentage of chromic acid or other
suitable depolarizer, and, by reason of the absence of local electrical action, the
pickling is performed very evenly or uniformly over the entire surface of the metal
article.
A further advantage afforded by my invention is, that it enables me, as above
mentioned, to entirely obviate the nuisance that arises from the offensive effluvia
produced by the ordinary pickling process.
It is evident that my invention is applicable for the pickling of metal articles
to prepare the same for treatment in various ways, such, for example, as tinning or
zincing, or simply for the purpose of cleaning such articles. The pickling of iron
preparatory to coating the same with tin, zine or lead can be very conveniently
and advantageously effected by my improved process, especially when chromic
acid is mixed with the sulphuric acid solution, and the negative plates or elements
used are of amorphous platinized carbon.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
First. The herein described process of pickling metals or alloys, wherein one
or more negative plates or elements of amorphous platinized carbon or other
suitable material, connected with an external circuit, are immersed in the pickling
solution, with or without the addition of a suitable depolarizer, and the article or
articles to be pickled are also connected with such external circuit and serve as the
positive plate or element, for the purposes above specified.
Second. The combination, with a pickling-vat, of one or more metallic supports
for the articles to be pickled, connected with an external circuit, and a negative
plate or element arranged within the said vat and also connected with the said
external circuit, substantially as, and for the purposes, specified..
Third. The use of a positive plate or element of iron in combination with a
negative plate or element of amorphous platinized carbon in an acid electrolyte in
which chromic acid is employed as a depolarizer, substantially as, and for the
purposes, specified.
Fourth. The use, in a pickling-vat, of a negative plate or element of amorphous
platinized carbon made in the form of a grid or grating, as, and for the purposes,
specified.
Fifth. The use, in a pickling-vat, of a negative element composed of wire-gauze
electroplated with silver and coated with amorphous platinum black, in combina-
tion with an acid electrolyte containing a nitrate depolarizer, as, and for the
purposes, specified.
Dated the 21st day of December 1893.
ARTHUR JAMES SMITH.
D. Young & Co.,
11 & 12, Southampton Buildings, London, W.C.,
Agents for the Applicant.