Electro-chemical Process for Cleaning Metal Surfaces.
Year: 1899

page_text: Date of Application, 3rd Oct., 1899
Complete Specification Left, 21st June, 1900-Accepted, 3rd Oct., 1900
PROVISIONAL
SPECIFICATION.
Electro-chemical Process for Cleaning Metal Surfaces.
We, the VEREINIGTE ELEKTRICITÄTS-ACTIENGESELLSCHAFT and JOSEF KLAUDY,
Chemist, both of X Simmeringerstrasse No. 187, Vienna, in the Empire of
Austria, do hereby declare the nature of this invention to be as follows:-
The electro-chemical process for cleaning metal surfaces according to this
invention is based on the electrolysis of a sait solution, which is so effected that
an ion mostly the anion, superficially attacks the metal to be cleaned, which is
suspended as an anode, and, in connection with which a soluble metallic salt of
the acid of the electrolytic salt-in particular cases, of a similar, secondarily
formed, acid is produced. At the same time, the kation of the electrolytic sait
should be so selected, that it must form secondarily a soluble hydroxide on the
non-attackable cathode.
The two ion products must with the double decomposition effected in the bath
precipitate the metal, removed by the anode in the form of hydroxide
deposit, which can be recovered as a by-product, by means of fining and filtering
apparatus arranged in any known manner as preferred.
At the same time, however, and herein lies the essence of the invention, the
original electrolyte is formed again or, in special cases, (with nitrates, chlorides,
etc.,) a salt of the same value as the original electrolyte in so far as, upon the
fresh decomposition thereof the continuous course of attack of the anode through
the anion, a soluble salt and one capable of being again precipitated by the kation
product being formed-is in no way disturbed.
This process can be employed for iron, copper, and similar metals.
With metals which can be better cleaned by the kation product, the process is
precisely inverted, the anode being unattackable, as with zinc, aluminium, and
similar metals.
Moreover, in all cases, at the beginning of the chemical action, the metal to
be cleaned is always used for a short time as a cathode, in order to effect the
removal of grease by the hydroxides of the electrolytic metal. Then only, by
the reversing of the direction of the current, the eventual cleaning off by the anion
begins.
The essentially practical point in this process however, is that the periodically
fined salt solution can be used over again thus avoiding any worthless or objection-
able waste-product.
The process is of the greatest importance for cleaning iron, in the carrying
out of which a solution of sulphate of soda may be advantageously used as
electrolyte and iron as a cathode.
Since in the process described, the electrolyte theoretically is not consumed,
certain electrolytic salts, which are more expensive than the acids hitherto
employed appear to be suitable for use, preferably the alkaline salts of all those
acids which, with the metal to be cleaned, produce a salt soluble in the bath.

page_text: The new electrolytic process described has further the following important
advantages as compared with the sulphuric acid cleaning process ordinarily
employed hitherto.
1. None of those waste products are produced, which frequently cause consider-
able inconvenience to the manufacturer, as he cannot himself put them to profit-
able use, and further dare not let them run off into a tank, for example, the acid
red-vitriol lyes of the acid cleaning process.
2. There is no material consumption of any active substance, with the excep
tion of the unavoidable small quantity consumed in working, as the actual working
consumption is limited to the electric current.
3. The manufacturer and the workman are spared the troubles arising from
the use of caustic acids.
4. The working is essentially uniform, as with the electrolytic process the
density of the cleaning bath and of the current are constant, whereas, in the
acid process the density of the mass diminishes as the formation of vitriol
increases, whereby, the action constantly becomes weaker. Moreover, for these
reasons, the acid can never be entirely used up.
5. The hydroxide of the cleaned off metal is secured, in an advantageous form,
as a by-product, in a solid shape, under this process, and can therefore be sold
directly, whereas, with the acid process, the residues can only be treated by an
expensive evaporation process and then only partially converted into a saleable
metallic compound, for instance, red vitriol.
6. The costs of the new process are only a fraction of those incurred with the
arid process.
Dated this 2nd day of October 1899
WHEATLEY & MACKENZIE,
40, Chancery Lane, London, W.C.,
Agents.
Electro-chemical Process for Cleaning Metal Surfaces.
We, the VEREINIGTE ELEKTRICITÄTS-ACTIENGESELLSCHAFT and JOSEF KLAUDY,
Chemist, both of X, Simmeringerstrasse 187, Vienna, in the Empire of Austria,
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 follow-
ing statement:-
The electro-chemical process for cleaning metal surfaces according to this
invention is based on the electrolysis of a salt solution, which is so effected that
an ion mostly the anion, superficially attacks the metal to be cleaned, which is
suspended as an anode, and in connection with which a soluble metallic salt of
the acid of the electrolytic salt-in particular cases, of a similar secondarily
formed acid is produced. At the same time, the kation of the electrolytic salt
should be so selected, that it must form secondarily a soluble hydroxide on the
non-attackable cathode.
The two ion products must with the double decomposition effected in the bath
precipitate the metal, removed by the anode product in the form of hydroxide
deposit, which can be recovered as a by-product, by means of fining and filtering
apparatus arranged in any known manner as preferred.
At the same time however, and herein lies the essence of the invention, the

page_text: original electrolyte is formed again or, in special cases (with nitrates, chlorides,
etc.) a salt of the same value as the original electrolyte in so far as, upon the
fresh decomposition thereof the continuous course of attack of the anode through
the anion, a soluble salt and one capable of being again precipitated by the kation
product being formed-is in no way disturbed.
The electrolytic salt solution is continuously or intermittently admitted whilst
the sludge, together with a part of the liquid, is carried off in the same measure,
to some ordinary fining or filtering apparatus as preferred from which the clear
regenerated liquid is always reintroduced into the process.
This process can be employed for iron, copper, copper alloys, and similar metals.
With metals which can be cleaned by the kation product, the process is
precisely inverted, the anode being unattackable, as with zinc, aluminium, and
similar metals.
Moreover, in all cases, at the beginning of the chemical action, the metal to
be cleaned is always used for a short time as a cathode, in order to effect the
removal of grease by the hydroxides of the electrolytic metal. Then only, by
the reversing of the direction of the current, the eventual cleaning off by the anion
begins.
The essentially practical point in this process however, is that the periodically
fined salt solution can be used over again thus avoiding any worthless or objection-
able waste product.
The process is of the greatest importance for cleaning iron, in the carrying
out of which a solution of sulphate of soda may be advantageously used as
electrolyte and iron as a cathode.
Since in the process described, the electrolyte theoretically is not consumed,
certain electrolytic salts, which are more expensive than the acids hitherto
employed appear to be suitable for use, preferably the alkaline salts of all those
acids which, with the metal to be cleaned, produce a salt soluble in the bath.
The electro-chemical cleaning process for zinc and aluminium is carried out
as follows:
The zinc or aluminium objects are introduced as cathodes into the electrolytic
bath and a solution of sulphate of soda or of a salt acting similarly is employed
as electrolyte.
The new electrolytic process described has further the following important
advantages as compared with the sulphuric acid cleaning process ordinarily
employed hitherto.
1. None of those waste products are produced, which frequently cause consider-
able inconvenience to the manufacturer, as he cannot himself put them to profit-
able use, and further dare not let them run off into a tank, for example, the acid
red-vitriol lyes of the acid cleaning process.
2. There is no material consumption of any chemical substance, with the excep-
tion of the unavoidable small quantity consumed in working, as the actual working
consumption is limited to the electric current.
3. The manufacturer and the workman are spared the troubles arising from
the use of caustic acids.
4. The working is essentially uniform, as with the electrolytic process the
density of the cleaning bath and of the current are constant, whereas, in the
acid process the density of the mass diminishes as the formation of vitriol
increases, whereby, the action constantly becomes weaker. Moreover for these
reasons, the acid can never be entirely used up.
5. The hydroxide of the cleaned off metal is secured, in an advantageous form,
as a by-product in a solid shape, under this process, and can therefore be sold
directly, whereas, with the said process, the residues can only be treated by an
expensive evaporation process and then only partially converted into a saleable
metallic compound for instance, red vitriol.
6. The costs of the new process are only a fraction of those incurred with the
acid process.

page_text: Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed, I declare that what
I claim is:-
1. An electro-chemical process for cleaning metal surfaces, consisting in sus-
pending the metal to be cleaned as a cathode in a salt solution to remove all greasy
matter, and afterwards changing the metal to be cleaned to an anode, the
electrolyte being so selected that secondary ion products are produced, which
by double decomposition, precipitate in the bath the dissolved metal in the form
of hydroxide deposit, whilst the original electrolyte, or one which is only so far
convertible into another salt that the continuous process of metallic dissolution
is in no way impeded-is re-formed.
2. An electro-chemical process for cleaning metal surfaces, consisting
in suspending the metal to be cleaned as a cathode in a salt solution, the
electrolyte being so selected that 'secondary ion products are produced, which
by double decomposition, precipitate in the bath the dissolved metal in the form
of hydroxide deposit, whilst the original electrolyte, or one which is only so far
convertible into another salt that the continuous process of metallic dissolution
is in no way impeded is re-formed.
3. As electrolytes for this process, solutions of salts, the bases of which form
in the bath a soluble hydroxide, for instance, an alkaline metal, and the acid
of which forms a salt of this base, which is soluble in water, and a salt of the
metal to be cleaned, which is soluble in the bath.
4. A process mentioned under Claims 1 and 2 for cleaning iron, copper and
copper alloys, with the employment of an electrolyte of the nature mentioned
under Claim 3,-sulphate of soda for example.
5. For the purpose of this process, the arrangement under which the electrolytic
salt solution is continuously or intermittently admitted, whilst the sludge, together
with a part of the liquid, is carried off in the same measure, to some ordinary
fining or filtering apparatus as preferred, from which the clear regenerated liquid
is always re-introduced into the process.
Dated this 21st day of June 1900
WHEATLEY & MACKENZIE,
40, Chancery Lane, London, W.C.,
Agents.