An Improved Process for Obtaining Permanent Deposits of Metals on Aluminium.
Year: 1899

page_text: Date of Application, 4th Sept., 1899
Complete Specification Left, 5th June, 1900--Accepted, 4th Aug., 1900
PROVISIONAL SPECIFICATION.
An Improved Process for Obtaining Permanent Deposits of Metals on
Aluminium.
We, EDWARD MIES, of 41, Bergstrasse, Heidelberg, and AUGUST HERMANN MIES
of Büdesheim am Scharlachberg Rhenish Hesse, both in the Empire of Germany,
Student of Chemistry and Physics and Grand Ducal Burgomaster and Vineyard
Proprietor respectively, do hereby declare the nature of this invention to be as
follows:-
:-
This invention has for its object a process for the production of permanent
deposits of metals on aluminium.
Among the processes at present known for obtaining deposits of other metals
on aluminium, there is none which has for its object an actual deposition directly
on aluminium. For instance, aluminium has first to be prepared in a solution
of cyanide of mercury whereby of course an amalgam is formed and another
netal such for instance as copper is then deposited on the amalgam. This pro-
cess is suitable for purposes of demonstration but not for practical working.
Metallic deposits should also bear a great degree of heat without losing their
thorough coherence. But this is not the case with the above mentioned method,
as it is well known that amalgams when heated lose the mercury and the latter
when heated must find some way out whereby the metal on the amalgam is
necessarily loosened.
In another process, aluminium is first treated with potash lye, the said lye
not being washed off and then the metallic deposition is directly effected thereon.
The drawbacks of such a process appear from the following.
If metallic aluminium be dipped in a lye, for instance potash lye, there is
formed aluminate of potash or aluminous oxide of potassium according to the
hydrogen being given off.
It is thus impossible to produce a permanent deposit on metallic aluminium,
as the lye cannot be washed off and the whole surface of the metal is coated with
aluminous oxide of potassium.
If it be further considered that potash lye is also mechanically retained by
the aluminous oxide of potassium there must take place a further evolution of
gas as the aluminous oxide of potassium is not washed off, which evolution of gas
prevents a firm adherence of the deposit on the aluminium. Even if in many
cases, a firm connection of the deposited metal on the aluminium appears at
first, that is to say immediately after the deposit is formed, to be solidly estab-
lished yet after a certain time the coating always becomes loosened when formed
by the methods hereinbefore described.
The process which forms the object of the present invention removes these
drawbacks and is entirely different from the processes hereinbefore mentioned.
The inventor, recognising the defects of previous processes has directed his main
attention to producing actual permanent deposits of metals on aluminium, which
deposits resist any influences and comply with all requirements which galvanic
deposits can be called upon to meet.
In this improved process, the metallic aluminium in the form of sheets, wire
or the like is heated for about five minutes in a boiling solution of phosphate of

page_text: soda and sulphate of magnesia, slightly acidulated with sulphuric acid, then
washed with water and subjected to the action of the electric current in the ordi-
nary baths of metallic salts, such as copper, zinc, tin or the like.
By the boiling with the above named salts the structure of the aluminium is
so changed (that is to say, a physical and not a chemical alteration, as in the
processes at present known, takes place) that it becomes very capable of receiving
other metals and metallic deposits and draws the same on to itself with great
force, so as to be inseparably combined therewith. By this improved process,
numerous depositions in baths of copper, zinc, tin and the like have been obtained
which are all characterized by the inseparability of the deposits from the
aluminium. No after evolution of gas and no scaling off when heated is here
possible and all the known disadvantages of other processes are avoided.
In place of phosphate of soda and sulphate of magnesia, a mixture of any
other phosphate compound and any other compound which attacks aluminium
may be employed.
If it be desired to plate aluminium treated by this improved process without
employing the electric current, the aluminium treated with the acidulated
solution herein before described is simply immersed when cooled, in the metal
bath in question (for instance a bath of tin, zinc, copper, nickel or the like) by
which means there also results a permanent nietallic coating.
Dated this 2nd day of September 1899.
W. P. THOMPSON & Co.,
Of 6, Lord Street, Liverpool, Agents for the Applicants.
COMPLETE SPECIFICATION.
An Improved Process for Obtaining Permanent Deposits of Metals on
Aluminium.
We, EDWARD MIES, of 41, Bergstrasse, Heidelberg, and AUGUST HERMANN MIES
of Büdesheim am Scharlachberg Rhenish Hesse, both in the Empire of Germany,
Student of Chemistry and Physics and Grand Ducal Burgomaster and Vineyard
Proprietor respectively do hereby declare the nature of this invention and in
what manner the same is to be performed, to be particularly described and ascer-
tained in and by the following statement :-
-
This invention has for its object a process for the production of permanent
deposits of metals on aluminium.
Among the processes at present known for obtaining deposits of other metals
on aluminium, there is none which has for its object an actual deposition directly
on aluminium. For instance, aluminium has first to be prepared in a solution
of cyanide of mercury whereby of course an amalgam is formed and another
metal such for instance as copper is then deposited on the amalgam. This pro-
cess is suitable for purposes of demonstration but not for practical working.
Metallic deposits should also bear a great degree of heat without losing their
thorough coherence. But this is not the case with the above mentioned method,
as it is well known that amalgams when heated lose the mercury and the latter
when heated must find some way out whereby the metal on the amalgam is
necessarily loosened.
In another process, aluminium is first treated with potash lye, the said lye
not being washed off and then the metallic deposition is directly effected thereon.
The drawbacks of such a process appear from the following.
If metallic aluminium be dipped in a lye, for instance potash lye, there is
formed aluminate of potash or aluminous oxide of potassium, according to the
formula:.
Al₂ + 6KOH
==
AL(OK) + 3H,
hydrogen being given off.

page_text: It is thus impossible to produce a permanent deposit on metallic aluminium,
as the lye cannot be washed off and the whole surface of the metal is coated with
aluminous oxide of potassium.
If it be further considered that potash lye is also mechanically retained by
the aluminous oxide of potassium there must take place a further evolution of
gas as the aluminous oxide of potassium is not washed off, which evolution of gas
prevents a firm adherence of the deposit on the aluminium. Even if in many
cases, a firm connection of the deposited metal on the aluminium appears at
first, that is to say immediately after the deposit is formed, to be solidly estab-
lished yet after a certain time the coating always becomes loosened when formed
by the methods herein before described.
The process which forms the object of the present invention removes these
drawbacks and is entirely different from the processes hereinbefore mentioned.
The inventors, recognising the defects of previous processes have directed their
main attention to producing actual permanent deposits of metals on aluminium,
which deposits resist any influences and comply with all requirements which
galvanic deposits can be called upon to meet.
In this improved process, the metallic aluminium in the form of sheets, wire
or the like is heated for about five minutes in a boiling solution of phosphate of
soda and sulphate of magnesia, slightly acidulated with sulphuric acid, then
washed with water and subjected to the action of the electric current in the ordi-
nary baths of metallic salts, such as copper, zinc, tin or the like.
A good
strength of boiling solution consists, for example, of 20 kilogrammes of phosphate
of soda & 10 kilogrammes of sulphate of magnesia to 100 litres of boiling water.
By the boiling with the above named salts the structure of the aluminium is
so changed (that is to say, a physical and not a chemical alteration, as in the
processes at present known, takes place) that it becomes very capable of receiving
other metals and metallic deposits and draws 'the same on to itself with great
force, so as to be inseparably combined therewith. By this improved process,
numerous depositions in baths of copper, zinc, tin and the like have been obtained
which are all characterised by the inseparability of the deposits from the
aluminium. No after evolution of gas and no scaling off when heated is here
possible and all the known disadvantages of other processes are avoided.
In place of phosphate of soda and sulphate of magnesia, a mixture of any
other phosphate compound and any other compound which attacks aluminium
may be employed, i.e. phosphoric acid, and phosphates of metals, such as phos-
phate of potassium, magnesium or aluminium.
If it be desired to plate aluminium treated by this improved process without
employing the electric current, the aluminium treated with the acidulated
solution hereinbefore described is simply immersed when cooled, in the metal
bath in question (for instance a bath of tin, zinc, copper, nickel or the like) by
which means there also results a permanent metallic coating.
Having now particularly described and ascertained the nature of our said in-
vention and in what manner the same is to be performed, we declare that what
we claim is:-
The process for depositing metals on aluminium, consisting in the aluminium
being boiled in an acidulated solution of a mixture of sulphate of magnesia and
phosphate of soda or a mixture of any other suitable phosphate compound and
some compound which attacks aluminium and after the washing of the article,
the deposition being effected in a solution of metallic salts, by means of the electric
current or without employing the same, substantially as hereinbefore set forth
Dated this 2nd day of June 1900.
W. P. THOMPSON & Co.,
Of 6, Lord Street, Liverpool, Agents for the Applicants.