Improvements relating to the Coating or Plating of Aluminium or Alloys thereof with other Metals.
Year: 1895

page_text: Date of Application, 19th Mar., 1895-Accepted, 3rd Aug., 1895
COMPLETE SPECIFICATION.
Improvements relating to the Coating or Plating of Aluminium or
Alloys thereof with other Metals.
I, WILLIAM HENRY LEGATE, of Number 38 Capen Street, in the City of
Hartford, County of Hartford, State of Connecticut, United States of America,
Gold and Silver Plater, 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:-
The object of my invention is to provide a method of and means for plating upon
aluminium or alloys thereof without regard to the special material used for such
purpose.
To this end my invention consists in the process, and in the combination of the
several steps of the process and materials to constitute the several baths and
solutions, as more particularly hereinafter described and pointed out in the claims.
Referring to the drawings:
Figure 1 is a diagram view illustrating an arrangement of the several solutions
and dips.
Figure 2 is a diagram view illustrating the arrangements of the whiteners.
A great many attempts have been made and experiments tried to secure a method
of covering or protecting the surface of an article made of aluminium or an
aluminium alloy with a surface layer of metal more durable or of higher value, but
the difficulty in all prior methods has been to produce a plated surface which would
hold firmly and not strip or peel off.
As commercially used in the manufacture of various articles, whether for use or
ornament, aluminium is usually mixed with an alloy, as zinc, copper and antimony,
for the purpose of making it hard and durable, but whether the aluminium be used
in a pure state or be alloyed with another metal my improved method is applicable
for plating upon the surface of such pure or alloyed aluminium.
In the practice of my invention certain solutions and baths are used, the first
being what I call a cleaning solution or pickle and is prepared as follows:
To each gallon of water used add three and one half ounces of oil of vitriol and
eight pennyweights of boracic acid, these being well stirred together. In this pickle
the article to be plated is suspended and allowed to remain for about an hour.
A rinsing solution of potash of a density of twelve degrees by a Tagliabue's
actino-hydrometer (such, for example, as is described in E. L. Wilson's "Quarter
Century in Photography ") is prepared and kept in a separate vessel, preferably a
kettle having a coiled steam pipe in the bottom so that this solution may be kept at
For washing
a temperature of at least two hundred and twelve degrees Fahrenheit.
the articles a tub or tank of running water, preferably prepared with a delivery tube
discharging in the bottom of the tank and an overflow formed at the top is provided,
the object of this being to have all of the waste material washed off from the article
and carried away by the flow of the water.
There is also provided what 1 term a dark dip which should be kept at a
temperature of about one hundred degrees Fahrenheit, there being preferably
used a kettle with a pipe leading into it to heat the solution and within the
kettle a jar, the latter holding the dip. This dark dip is made by mixing with

page_text: each gallon of sulphuric acid four pounds of nitrate of soda, two ounces of muriatic
acid and three and one-half pennyweights of flaky carbon, as soot.
The solution
should stand at about fifty degrees by hydrometer (Beaume). The object of the
carbon (soot) in this dark dip is to preserve the white color of the metal and
to keep it from corroding, while the nitrate of soda dissolving freely in the
sulphuric acid has about the same function as nitric acid when used as a dip for
articles of German silver or copper.
After the article to be plated has been treated in the above solutions and dips in
a manner which will be hereinafter described they are subjected to treatment in
what I call the whiteners, two of the latter being used and compounded and prepared
as follows:
The first whitener is prepared by mixing with one gallon of water one and one-
half gallons of concentrated liquid ammonia and four pounds of cyanide of
potassium, three and one-half pounds of chloride of zinc, five ounces of carbonate
of potassium and eight pennyweights of white arsenic. This same proportion of
the several ingredients to the gallon will be preserved in mixing up a larger
quantity. If it shall be found on test that the metal used. as a. plate does not
deposit promptly and evenly the whitener should have a slight proportion more
of ammonia mixed with the solution, this precise quantity of ammonia required
in the whitener for treating different alloys of aluminium being to a slight degree
only a matter of experiment and skill. This first whitener should be of a density
of about ten degrees by actino-hydrometer (Tagliabue) test and should be kept at
a temperature of about one hundred degrees Fahrenheit..
A second whitener is prepared by mixing with each gallon of cold water one and
one-half gallons of concentrated ammonia, two pounds of cyanide of potassium,
twelve ounces of carbonate of soda, four ounces of chloride of copper and five
penny weights of white arsenic; the above proportion of chloride of copper to be
increased slightly to provide a more perfect deposit of copper.
If the copper-
coated plate blisters increase slightly the proportion. of cyanide of potassium.
This solution fills up the pores of the metal, protects the slight percentage of iron
present in the aluminium and brings up a good, clear color on the work. This
second whitener should stand at a density of about ten degrees by an actino-hydro-
meter (Tagliabue) and should be kept at a temperature of about one hundred degrees
Fahrenheit.
Iron kettles are preferred for holding the whiteners, and the desired colors
designed to be produced by the use of these whiteners can be brought out by
increasing slightly the temperature of the solution.
In the accompanying drawings the letter A denotes the solution terined a pickle;
the letter B the water bath; C the potash solution and D the dip, and an article
to be plated is treated in these several solutions in the order denoted by the
numerals.
It is first placed in the pickle A and allowed to remain there for about an hour.
Second, it is then rinsed in B, then, third, quickly dipped into the potash solution
and promptly removed; then, fourth, it is washed in the water B, then, fifth,
plunged once or twice into the carbon dip D, and, sixth, finally again washed in
water B.
The letter E denotes a battery, or like source of electric energy, Fa switch board,
the negative conductor, h, the positive wire, I the zinc whitener and K the copper
whitener. The solutions in these whiteners are arranged in suitable vessels, the
positive wire having suspended from it, in the one bath, the zinc anodes i, i¹ and, in
the other, the copper anodes k k¹. The negative rod L is counected to the
negative wire g and arranged so that the articles to be whitened are suspended from
this rod.
Having prepared an article in the dips and solutions before described it is
suspended from the rod L until from the action of the solution it is seen that a
sufficient layer has been deposited, this being a matter which calls for the skill of
the plater in his knowledge of the art. Then remove the article from the zinc

page_text: whitener and rinse it in cold water:. Then: suspend the article from the negative
rod L in the copper whitener and deposit in that bath a layer of copper.
The article, whether it be of pure aluminium. or aluminium alloy, is ready for
the plating of other metal, as gold, silver, nickel, or the like, after a preliminary
rinsing in water.
Careful and thorough tests of the methods and means above described have shown
that a layer of any of the other metals may be plated upon the aluminium and a
perfect adhesion of the plating layer secured that may be rolled, bent or otherwise
subjected to severe compression or tensile or twisting strains without cracking,
blistering or peeling off.
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:
1. The method of pickling aluminium to prepare it for plating, which consists in
subjecting the metal to treatment in a bath consisting of a solution in each gallon of
water, of three and one-half ounces of sulphuric acid, and eight penny-weights of
boracic acid, all substantially as described.
2. As a step in the method of preparing aluminium for plating, the immersion of
the metal in a solution made up in the proportion of one gallon of sulphuric acid,
four pounds of nitrate of soda, two ounces of muriatic acid, and three and one-half
pennyweights of flaky carbon as soot, of a density of substantially fifty degrees by
hydrometer (Beaume), all substantially as described.
3. As a step in the method of preparing aluminium for plating, the immersion of
the metal in a solution of sulphuric acid, nitrate of soda, muriatic acid and flaky
carbon as soot, all substantially as described.
4. As a step in the preparation of aluminium for plating, the treatment of the
metal in a bath consisting of the following ingredients in the proportion stated, one
gallon of water, one and one-half gallons of concentrated liquid of ammonia, four
pounds of cyanide of potassium, three and one-half pounds of chloride of zinc, five
ounces of carbonate of potassium, and eight pennyweights of white arsenic, all
substantially as described.
5. As a step in the preparation of aluminium for plating, the treatment of the
metal in an electro plating bath made up in the proportion substantially of one
gallon of water, one and one-half gallons of concentrated ammonia, two pounds of
cyanide of potassium, twelve ounces of carbonate of soda, four ounces of chloride of
copper, and five pennyweights of white arsenic, all substantially as described.
6. The method of plating aluminium, which consists first, in subjecting the metal
to treatment in a pickling bath consisting of a solution of three and one-half ounces
of sulphuric acid, eight pennyweights of boracic acid to each gallon of water, then
rinsing the article in water, then rinsing the article in a warm solution of potash,
then washing the article in water, then treating it in a bath consisting in a solution
substantially to each gallon of sulphuric acid of four pounds of nitrate of soda,
two ounces of muriatic acid, and three and one-half pennyweights of flaky carbon
as soot, then plating it in a bath consisting substantially to each gallon of water of
one and one-half gallons of liquid ammonia, four pounds of cyanide of potassium,
three and one-half pounds of chloride of zinc, five ounces of carbonate of potassium,
and eight pennyweights of white arsenic, then further plating the article in a bath
compounded substantially by mixing with each gallon of water, one and one-half
gallons of concentrated ammonia, two pounds of cyanide of potassium, twelve ounces
of carbonate of soda, four ounces of chloride of copper and five pennyweights of
white arsenic, and then finally coating with the desired metal in a plating bath in
the ordinary manner, all substantially as described.
7. The method of plating aluminium which consists in subjecting the metal to
treatment in a pickling bath, then rinsing the metal in water, then washing in a
potash solution, then washing it in water, then treating it in a solution in which
Haky carbon, as soot, is an ingredient, then plating the metal with a layer of zinc,

page_text: then plating it with a layer of copper, then rinsing the metal in water, and finally
plating it in an ordinary bath with a metal desired, all substantially as described.
Dated this 20th day of November A.D. 1894.
WILLIAM HENRY LEGATE.
D. Young & Co.,
11 & 12 Southampton Buildings, London, W.C.,
Agents for the Applicant.