Improvements in or connected with the Preparation or Coating of Aluminium Surfaces, and in Alloys or Metallic Mixtures therefor, and for Soldering.
Year: 1894

page_text: Date of Application, 27th Apr., 1894
Complete Specification Left, 25th Jan., 1895-Accepted, 9th Mar., 1895
PROVISIONAL SPECIFICATION.
Improvements in or connected with the Preparation or Coating of
Aluminium Surfaces, and in Alloys or Metallic Mixtures therefor,
and for Soldering.
I, HUGH RAMAGE, of The Royal College of Science, Dublin, in the County
of Dublin, Chemist, do hereby declare the nature of this invention to be as
follows:-
My invention relates to the preparation or coating of aluminium with metals,
alloys or metallic mixtures, whereby surfaces are produced which retain their
brightness in air, and upon which other metals may be deposited, electrically or
chemically and with which melted metals unite or alloy easily. The materials used
to form the said surfaces may also be used as solders for the metal and the surfaces
may be formed and the pieces soldered together in one operation, or solders of
different composition may be used on these surfaces, with or without the use of
a flux.
B
The substances I use to unite with the aluminium to form the surfaces above
referred to are by preference such as have a low melting point and of the single
metals fulfilling this condition, zinc and tin I find are the best but cadmium or
lead may be used, but cadmium while not as suitable as the first mentioned metals,
is much better than lead. The alloys and mixtures of metals may be of various
compositions but those I prefer are composed of zinc with either tin or cadmium or
with both of these metals. It is a property of these, when made in certain pro-
portions, that on cooling after perfect fusion, they deposit metallic crystals for a
considerable time before the temperature of complete solidification is reached.
I have found that certain amalgains produce a bright surface on aluminium but
the mercury would volatilise during the process of soldering and would injure the
workmen's health.
Having prepared the metal, alloy or mixture of metals 1 divide it into pieces of
suitable size and place these on the surface of the aluminium to be treated:
then heat the two by any convenient means, (the nonluminous gas flame answers
very well) to a temperature about that at which the pieces of metal on the
aluminium become quite liquid. The source of heat may then be removed and the
metal, in the fluid or partially fluid state, rubbed on the aluminium with a rubber
or brush of suitable material. I prefer a rubber made of asbestos fibres bound
together with thin wire but any form of rubber, made of any material which does
not decompose appreciably at the temperature required by the process, may be
.used. For some work a solid piece of the metal may be rubbed on the hot
aluminium.
The alloys or mixtures of metals, possessing the property of crystallising as above
described, deposit crystals on the rubber which retain sufficient of the still liquid
metal to coat the aluminium when the skin on this metal is removed by gentle
rubbing.
Instead of using the metal, alloy or mixture of metals in small pieces as described
1 find it preferable sometimes to keep it in the liquid state in a crucible. When the
rubber is dipped in this, sufficient of the liquid adheres to prepare a considerable
surface of the hot aluminium.

page_text: If it be desired to prepare only a limited area, the remainder may be protected
by placing over it a thin piece of foil containing a hole of the shape of the surface
which is to be prepared.
One of the mixtures I have found satisfactory is made by melting one part of
zinc in a clay crucible and adding to it one part of cadmium and then two parts
of tin. It commences to solidify at about 200° C. and is completely solid at
about 156° C.
In soldering aluminium thus prepared it is sufficient to bring the pieces together,
lay a piece of solder over the juncture and raise the temperature by any convenient
means to above the melting point of the solder when the latter at once unites and
on cooling solidifies and forms a sound joint. If preferred a soldering iron may be
used as in ordinary tin-plate soldering.
A useful soft solder is composed of equal parts of tin and cadmium which melts
at about 173° C.
071 1
Improvements in or connected with the Preparation or Coating of
Aluminium Surfaces, and in Alloys or Metallic Mixtures therefor,
and for Soldering.
1, HUGH RAMAGE, of The Royal College of Science, Dublin, in the County
of Dublin, 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 preparation or coating of aluminium with metals.
alloys or metallic mixtures whereby surfaces are produced which, as they do not
oxidize readily, retain their brightness in air and with which melted metals unite
or alloy directly with great ease. Other metals may also be deposited electrically
upon such surfaces after an ordinary pickling process. The materials used to form
the said surfaces may also be used as solders for the metal and the surfaces may be
formed and the pieces soldered together in one operation, or solders of various
composition may be used on these surfaces with or without the use of a flux.
The substances I use to unite with the aluminium to form the said surfaces are
alloys or mixtures of metals which, when heated to a sufficiently high temperature,
become perfectly liquid but which as they cool deposit metallic crystals and
become quite pasty before the point of complete solidification is reached. I have
found that zinc is the best metal for the purpose of giving the said metallic crystals
and that it may be combined either with tin or cadmium or with both of these
metals.

page_text: The following table gives the composition of various alloys
metals :-
or mixtures of
completely about 192° C.
I have found that whilst these alloys or mixtures are in the intermediate stage,
that is while the crystals and liquid are present together, they are exceedingly
effective in attacking the resisting surface on the aluminium and that a very gentle
rubbing suffices to cause the metal, alloy or mixture of metals and the aluminium
to combine at once. The mixture containing equal parts of zinc and tin is one of
the best as it has the greatest range of temperature during which it is in this
especially active condition. These alloys are best made by first melting the zinc
which has the highest melting point, in a clay crucible and adding the other metal
or metals to it. If complete fusion does not take place at once the mass must be
heated until it does. The alloy or mixture of metals may be kept in a melted
condition or it may, when solid, be divided into small pieces.
According to my invention I coat the aluminium as follows:-Pieces of the alloy
or mixture of metals are placed upon the aluminium to be treated and the whole
heated by any convenient means such as by the non-luminous gas flame or over a
clear fire or by placing it on any hot surface, until the alloy or metallic mixture
becomes quite liquid. If it be rubbed with a suitable rubber in its present con-
dition little or no action will result but as the metals cool the crystals, above
referred to, form and while they are forming, gentle rubbing causes the aluminium
to alloy with the other metals and the surface remains roughened by the crystals.
On reheating the aluminium these crystals melt and the surface becomes smooth
and bright.
The alloy or mixture of metals may, if preferred, be kept liquid and the rubber
may be dipped in or kept floating in the liquid. The rubber on being removed will
have sufficient of the alloy or metallic mixture adhering to it to coat a considerable
surface of the aluminium.
In cases where large surfaces have to he dealt with it would be advantageous to
have a special means of heating the aluminium so that the temperature at which
the action is best could be maintained. This would, however, leave the surface
roughened by the crystals and it would be necessary to raise the temperature of the
aluminium by some other apparatus in order to melt the crystals and cause them

page_text: to alloy with the aluminium. This would present no advantage, however, in the
case of small articles.
A rubber which is advantageously used to give the gentle rubbing required
according to my invention is made of a material which is not decomposed at the
temperature employed. I have succeeded best with asbestos fibres bound together
with wire or inserted tightly in a metal or glass tube, the latter being preferable
as only a short length of asbestos need protrude and as this wears away more may
be pushed down by pressing on the ends of the fibres in the tube.
If only a limited area of the aluminium is to be prepared the rest may be
protected by a shield of thin metal, mica, asbestos or a like material which retains
its shape at the working temperature and which does not decompose. Only that
part of the aluminium touched by the rubber is attacked and the soft fibres of the
asbestos reach up to the edges of the shield thereby enabling any sharply defined
area to be prepared.
Surfaces of aluminium thus coated or prepared may be soldered as follows:
The aluminium is heated to a temperature exceeding the melting point of the solder
and is brought into contact with the solder. The solder melts and unites with the
aluminium surface. Any ordinary solder may therefore be used and amongst others
I have found pure tin and pure cadmium to answer well, as also alloys or mixtures
of these with each other or with zinc.
A solder composed of equal parts of tin and cadmium is especially useful as it
possesses a low melting point and gives a joint of considerable strength.
Two pieces of aluminium may be soldered together by first preparing the edges,
which are to be united, and the surfaces immediately adjacent to these edges in the
manner herein before described, then bringing them together,. then heating them
above the melting point of the solder, and then drawing a strip of solder down the
surfaces whereby a portion of the solder melts and unites the two pieces of
aluminium. Or, only the edges need be prepared and when each is charged with
melted solder, they may be brought together, whereupon the solder unites and
when cold forms a sound joint. A hollow, closed body may thus be made from two
or more pieces previously shaped to suit requirements.
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 :-
:-
1. A method of preparing or coating the surface of aluminium with metals,
alloys or metallic mixtures which crystallize on cooling from the liquid state,
consisting in laying pieces of the metal, alloy or mixture of metals on the surface
to be treated, beating this surface in any suitable manner to a temperature at which
the metal, alloy or mixture of metals melts, allowing the liquid metal alloy or
mixture of metals to cool until crystals begin to form and then rubbing the surface
of the aluminium with a suitable rubber and finally in reheating the aluminium,
substantially as and for the purpose described.
2. A. modification of the method described in Claim 1 consisting in heating the
aluminium surface to be prepared, rubbing it with a suitable rubber which has been
dipped into the fused metal, alloy or mixture of metals and finally reheating the
aluminium, substantially as described.
3. The application of the processes described in Claims 1 and 2 to soldering
aluminium by first preparing or coating the aluminium surfaces to be soldered as
described, heating the prepared surfaces to a temperature above the melting point
of the solder, applying the solder and then bringing the surfaces thus prepared into
contact to form a joint, as set forth.
4. In carrying out the above described processes the use of a rubber consisting
of a material not decomposed by the working temperature and preferably asbestos
fibres bound together with wire or inserted or simply pressed tightly into a tube,
preferably of glass, so that only a short length of the asbestos projects, and of
bields of a material that is not decomposed or distorted at the temperature employed
"

page_text: such as thin metal, mica, asbestos, such shields being designed to protect those parts
of the surface of the aluminium which it is not desired to prepare or coat,
substantially as described.
Dated the 25th day of January 1895.
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicant.