Improvements in Process of Nickel Plating.
Year: 1896

page_text: Date of Application, 7th Apr., 1896-Accepted, 13th June, 1896
COME LEIE SIECIFICATION.
Improvements in Process of Nickel Plating.
I, HARRY LEOPOLD HAAS, of 526 West 25th Street, in the City, County and
State of New York, in the United States of America, Treasurer, 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 improvements in the art of nickel-plating, the objects
being (1) to more quickly accomplish the plating than heretofore, (2) to use an
electric current of small voltage, (3) to more uniformly, as regards thickness,
adhesion and color, accomplish the depositing of nickel upon the cathode, and (4) to
render unnecessary the addition, during the plating operation, of nickel-salts for
strengthening the plating bath, as heretofore.
In the accompanying drawing there is shown a partly-sectional view of a nickel-
plating bath, the source of electrical energy, which may be of any useful form,
being omitted.
In the said drawing, I have shown one form of apparatus which may be employed
in carrying out my new process of nickel-plating. A represents the box for
containing the electrolyte or solution, B. An anode, C, is partly immersed in the
solution. This anode differs from those used prior to my invention, in that it
presents to the electrolyte a much greater surface than is presented by a plane, flat
anode, and although other forms of nickel anodes constructed so as t, have an
increased surface may be employed with advantage, yet I prefer to use a corrugated
anode, made substantially as shown in the accompanying drawing. This anode is
suspended from a metallic rod, D, by means of hooks, F, F, and is connected by a
conductor, E, to the positive pole of the generator.
During the electrolysis, both the sulphate of nickel and the sulphate of ammonia
are decomposed, and sulphuric acid and ammonia are set free at the anode. The
sulphuric acid forms an equivalent quantity of sulphate of nickel by its action on
the anode which it dissolves.
If the amount of ammonia freed at the anode becomes too great, in proportion to
the amount of sulphuric acid set free, the, solution will, in a short time, become
weak in metal and decidedly alkaline, and it has also been found that the more
intense the current of electricity employed the more rapid will be the uneven
liberation of the ammonia and sulphuric acid, which will cause the quality of the
deposit of the nickel upon the cathode to become gradually poorer, in color and in
adhesiveness, because it has been found that the more intense the electric current
the more hydrogen is eliminated, which makes the deposit upon the cathode brittle
and strip, especially if the deposit is thick.
By the employment of an anode of nickel, which presents to the electrolyte a
much greater solid and continuous surface than would be the case if a plane flat
anode was used, I find that an electric current of very low intensity may be
employed, even as low as two volts, and that such current may be more uniformly
maintained, and that less ammonia is liberated than when a plane anode is used,
and I find, also, that a much greater amount of nickel is dissolved from the
continuous anode having a corrugated or equivalently-extended surface, because of
the increased surface presented, and that the strength of the bath is more uniformly
maintained, with the direct result that the nickel deposited upon the cathode is
more regular and uniform in color and thickness, adheres more tenaciously and
does not scale therefrom, as has been the case heretofore, due to excess of hydrogen
at the cathode by the deposited nickel.

page_text: 1 have also discovered that when the process having the continuous solid anode,
presenting an increased surface, is not used, that the strength of the solution will
not be uniform, for, if the anode surface is not considerably larger than that of the
article to be deposited upon, more nickel will be deposited on the work than is
dissolved from the anode, and all the sulphuric acid which is evolved at the anode
will not be dissolved to form sulphate of nickel, but will combine with some of the
ammonia, and the bath will become, in time, composed of sulphate of ammonia and
very little sulphate of nickel, thereby weakening the solution in nickel, and causing
the deposit to become dark in color. To overcome this objection, it has become
customary to add nickel-salts to the solution, as required, but, by the use of my
process, the addition of such salts is rendered unnecessary, due to the evenness
existing between the resolving of the anode into the solution and the deposition of
nickel upon the cathode. I have also found that when an anode having the
increased surface is employed, the increased size of the anode and its more even
solution into the bath, contribute to make the electrolyte a much better conductor
of the current than when the plane anode is employed, the objection heretofore
being that as the solution becaine weaker in nickel the resistance to the passage of
the current was increased and this difficulty rendered necessary the employment of
a current much higher in voltage than is required in connection with my new
process of plating, which use of a high current has been objectionable and
expensive.
One of the disadvantages due to the employment of currents of high voltage is
the tendency of the nickel to precipitate in the form of basic salts impairing the
metallic strength of the bath. This precipitation I prevent by the employment
of a current of low voltage and an anode presenting a greatly increased and
continuous surface to the solution.
The process of nickel-plating, therefore, differs from most, if not all, other
plating processes in that a substantially neutral solution must be employed, which
renders the rate of solution of the anode comparatively slow, and unequal to the
rate of deposit at the cathode, and this results in the necessity of constantly
replenishing the solution with salts of nickel to maintain the requisite strength
the solution. These difficulties are remedied by my invention, and the process
rendered substantially even and continuous as long as the anode lasts.
I especially disclaim from my invention, those forms of anodes which consist of
a number of non-integral masses contained in a perforated frame, which anodes are
entirely unfitted for the purpose of my invention, because of the imperfect
electrical and mechanical contact existing between the grains, which results in the
formation of an anode offering an enormous resistance to the passage of electricity.
My invention, on the contrary, contemplates the employment of a continuous
anode.
Having now particularly described and ascertained the nature of my said inven-
tion, end in what manner the same is to be performed, I declare that what
I claim is;
The process of nickel-plating herein described, which consists in employing, in
a substantially neutral solution, a continuous anode having a corrugated or
equivalently-extended surface, greater than would be presented by an anode of the
same length and breadth, and then passing an electric current through the anode
and the solution, and, by the use of such anede, balancing the solution of the anode
and the deposit at the cathode, whereby the metallic strength of the solution is
maintained substantially uniform, substantially as and for the purposes described.
Dated this 4th day of April 1896.
MARKS & CLERK,
18, Southampton Buildings, London, W.C., and
13, Temple Street, Birmingham, Agents.
MARKS & CLERK,
18, Southampton Buildings, London, W.C., and
13, Temple Street, Birmingham, Agents.