Improved Electro-plating Process and Apparatus therefor
Year: 1899

page_text: Reprinted
as amended in accordance with the decision of the Chief Examiner dated
the 22nd day of May 1901.
Date of Application, 16th May, 1899-Accepted, 24th June, 1899
COMPLETE SPECIFICATION (AMENDED).
66 'Improved Electro-plating Process and Apparatus therefor "..
I, EMILE LOUIS DESSOLLE, Chemical Engineer, of 3 Villa Beranger, Fontenays Bois,
in the Republic of France, 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:-
This invention relates to an electro-plating process as described hereunder and
illustrated in the accompanying drawing, in which :-
Figure 1 represents the apparatus used in the process, while
Figures 2 and 3 are detail views which will be referred to hereinafter.
The process, is intended chiefly to be used for plating cast metal and iron with
copper, but it may be used equally well with other metals.
The article to be plated say with copper must first be thoroughly cleaned in an
acid bath, or by means of a sand blast worked by either compressed air or
steam.
The object of this first cleaning is to get rid of the layer of oxide covering the
metal and to expose any flaws on the article to be plated, after which the article
receives its final touches by chiseling, filing etc. which can be effected much better
after such preliminary cleaning, since the tools bite better and the files are not so
quickly blunted, as when employed on the oxide layer of the metal.
The finishing touches having been carried out, the article is again cleaned, this
time, however, only by means of a sand blast after which it is placed in an alkaline
coppering bath, in which it is covered with a thin layer of copper, which is intended
to protect it against attack in the acid bath (copper sulphate, generally) in which it
is finally covered to the thickness required in order to effectually protect the article,
of cast iron or other metal, as the case may be, against premature decay, by which
process it acquires the appearance of copper or bronze.
This first coating having been effected, the irregularities on the surface, such as
holes, fissures and the like must be stopped up by filling them in with tin solder or
other metals, or alloys, either with the aid of the soldering iron, blow-pipe, or in any
other suitable way.
This filling up of the surface irregularities after the first coating is more easily
carried out at this stage, for the copper is very rapidly heated and soon acquires the
temperature necessary for the complete adhesion of the metal in the said irregularities.
After this the article is again passed over for the purpose of smoothing the surface and
removing any excess of the filling substance, and then again placed in the alkaline
bath so as to provide a new thin film of metal to cover the fillings, and finally in the
acid bath in which it is treated until the required thickness of the coating is obtained.
In order to render the deposition of metal very rapid, in other terms to work with
a current of very high density (about one thousand amperes per sq meter of the
cathode surface) the following arrangement has been bee devised..

page_text: At the bottom of the plating vessel a is arranged a serpentine or coiled tube or
tubes, provided with nozzles or, with simple holes, directed upwards, obliquely or
otherwise. This tube is in communication with an upper reservoir e into which the
liquid is forced by a tube d. The article to be plated is connected with the negative
conductor and placed between the anodes connected with the positive conductors in
the usual way; but the liquid spurting within the bath from the tube strikes against
the electrodes, and thus depolarizes them.
The overflow of the vessel a passes into another vessel e from which it is pumped,
as required, into the upper reservoir c. This vessel e is also provided with a coiled
tubes at the bottom, which is constantly traversed by steam, hot water, or hot air,
for the purpose of heating the liquid in the vessel before it is pumped into the
receiver c, which is arranged at a suitable height above the plating vessel a in order
that the jets of liquid may issue from the perforated tube or nozzle at a sufficient
pressure and force.
The heating is essential and should bring the acid bath to about blood heat and
the alkaline bath somewhat higher.
By this arrangement important advantages are obtained: first a much greater
density of current can be employed, because the electrodes, and especially the
cathodes, are always at full work, the impurities and gas bubbles which would cover them
if the electrolyte was still, being constantly swept away by the jets of the liquid;
secondly, the metallic deposits on the cathodes are uniform and regular, because the
hydrogen bubbles which ordinarily settle on them, are driven off by the jets of liquid
as described above; depolarization and a greater perfection in the work done is there-
fore ensured. It is a well known fact, that the electrolytic deposits obtained by the
ordinary methods produce rough, irregular surfaces as if formed by a succession of
small particles distributed according to the caprice of polarization.
An article presenting very pronounced projections and recesses is apt to be more
thickly coated on the former than on the latter. This results from the fact that the
recesses are generally hidden by the projections m (Figure 2), or, at any rate, are
more distant from the anodes; hence, in such places, as represented by 6 local
currents are formed which may even destroy the effect of a first good coating; for
the principal current has no effect in parts like those indicated by the shading lines,
in Figure 2, as can easily be understood. Besides, the distance x from the end of the
recess to the anode, is far greater, than the distance z from the same anode to the
projection m; from which it follows, that the electrical resistance along x is much
greater than that at , hence it is but natural that the deposit at x should be weaker
than that at 2.
In order to remedy this drawback double anodes may be employed, as represented
in Figure 3, whereby recesses may be coated as efficiently as projections. Into the
hollow part is introduced the double anode st, (touching the cathode as shown) which
receives the action of the current of the anode 8, within, say, the zone o negative at
this place, but positive as to the rest of its mass, and furnishing, consequently the
current necessary to plate the hollow into which the anode extends.
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 :-
I. An electro-plating process consisting in the following operations: (a) cleaning of
the article to be plated (b) touching it up; (c) cleaning it by means of a sand-blast;
(d) preliminary plating in an alkaline or neutral bath; (e) stopping and filling up
surface irregularities; (f) second plating in an alkaline or neutral bath; (g) final
plating in an acid bath with jets substantially as described.
2. In apparatus-for use in electro plating-articles, a-plating vessel-provided at the
bottom with-a-serpentine or coiled pipe pierced-with-holes-or-provided-with-nozzles
communicating with-an-upper reservoir-fed-by-means-of-a force pump-or-equivalent
into the tank of which the overflow-from-the-plating-vessel-is-discharged-and-which
tank is provided with means for heating the liquid before it is pumped up into the

page_text: reservoir-whenee-it-descends-under-pressure-into-the-plating vessel,-issuing from-the
nozzles or perforated pipes-in-jets-against-the electrodes substantially-as-and-for-the
purpose-described.
2. 3. In apparatus for electro-plating articles a double anode arranged to extent
extend into the recesses of the article to be plated for the purpose of obtaining a
deposit of uniform thickness, substantially as described.
3. 4. The complete apparatus for use in electro-plating substantially as described
or illustrated in Figure 1 of the accompanying drawings.
1000