Stories of electroplating technology - The Woolrich generator and its first industrial application in an electroplating plant

With the discovery of magnetic induction by M. Faraday (1791-1867) and the subsequent development from 1832 onwards with the aim of generating electrical energy through magnetically induced machines, many attempts were made by Pixii, Saxton, Clark, Stöhrer and others to find applications, primarily for "medical purposes" (Fig. 1).

Fig. 1: Principle of the early generators [1]It was another decade before the first industrial use was made of the generator known at the time as the "magnetic-electric induction machine".

As a young chemist, John Stephen Woolrich (1820-1850) from Birmingham came up with the idea of using this energy instead of Daniell's or Bunsen's cells to produce metallic coatings. In 1842, Woolrich was granted British patent 9431 for the use of an electric generator in electroplating instead of batteries. He lacked the money and resources to build his own electroplating plant. Once he had found a financial backer in the Elkingtons, he was able to start using the generator on an industrial scale. He set up a factory in London, where a small steam engine set several magnetic machines in motion for gilding and silver-plating metal articles [2]. However, he was not granted great success, as he died very young in 1850 at the age of 29.

In 1844, however, Woolrich also had a "colossal magnetic machine" made for the Elkingtons (Elkington Silver Electroplating Works) by Prime & Son, another Birmingham company, which they were to use for silver-plating spoons, forks and other "table utensils" made of nickel silver.

The design of the generators would today be described as permanently excited direct current machines with 4 and later 8 magnetic iron magnets, arranged in the shape of a horseshoe, alternating in polarity and evenly distributed around the rotor (Fig. 2).

The rotor consisted of 6-10 axial bobbins wound with silk-wound copper wire and rotated with an iron core through the magnetic poles (Fig. 2). The current was tapped via a commutator so that the polarity remained the same and thus a direct current was generated. The number of windings and optimized speed had to be selected so that the desired process data for electrodeposition was achieved. Many optimization attempts were certainly made in this regard, which are unfortunately no longer documented today. The electrical parameters of current and voltage, as we know them today, were not yet defined at that time. The process control was described in [2] as follows: "The weight of the gold, silver etc. deposited on the surface of metal objects in a certain time varies, on the one hand, according to the number of revolutions of the machine and the content of the metal solution in which the object is immersed, and on the other hand, according to the distance of the ends of the armature from the magnetic poles; the larger the surface of the object, the closer the magnet must be brought to the armature; the smaller it is, the greater the distance must be." [sic! [sic!].

Fig. 3: Commutator of the Woolrich generator [4]A major problem was the maintenance of the air gap and the associated stability of the bearings and the wear elements of the commutator (Fig. 3), whereby many optimizations were undertaken in the application.

It is reported that M. Faraday paid a visit to Prime & Son's Works in the 1840s on the occasion of the meeting of the British Association in Birmingham, together with some of his scientific friends. He expressed his great pleasure at the further development of his great research, that his discovery had been applied so early and extensively and put into practice so successfully [5].

In 1852, however, M. H. Jacobi's calculations on economic efficiency compared to the cells commonly used at the time led to a negative result. "From all these formulas, which by their generality apply to all electromagnetic machines, a conclusion can be drawn as to the applicability of this force for industrial purposes ... in terms of maintenance costs, it is inferior to all conventional motors." [sic!] [6]. Improved economic efficiency was to come later.

With the investment and application of Woolrich's magnetic induction machine by the Elkingtons, it became the first industrially used generator in history to be driven by a steam engine (Fig. 4). In 1863, it was reported that "... where a hard layer of silver is required, the electric current is produced by a magneto-electric machine, which is moved by a steam engine; a very intense current is thus obtained, which slowly precipitates the silver, making it very hard and compact..." [8]. [sic!] [8].

Fig. 4: Illustration from Messrs. Elkington, Mason & Co's Electro-Plate Works, Newhall-Street, Birmingham [7], "In the illustration in the middle of the first page, the vats for plating may be seen to the right of the Magneto-Electric machine"

However, the breakthrough of large-scale energy generation using generators would not come until later. The basis for this was the use of electromagnets, which were powered by the self-excitation of the current produced by the generator. The basis for this was created almost simultaneously by W. Siemens and C. Wheatstone with their discovery of the electrodynamic principle. Gramme's dynamo machine [9], which was based on this principle, was first used on an industrial scale from 1875 at the Norddeutsche Affinerie for electrolytic copper refining (see also [10]).

Literature

[1] Engelmeyer, P. C. v.: Uebersicht über Dynamo- maschinen, Polytechnisches Journal, Vol. 292, 1894, 10-16
[2] NN.: Ueber die Anwendung der magnet-elektrischen Maschine zum Versilbern und Vergolden der Metalle, Polytechnisches Journal, Vol. 107, 1848, No. XIII, pp. 55-57
[3] https://commons.wikimedia.org/w/index.php?curid=38742153
[4] https://upload.wikimedia.org/wikipedia/commons/f/fd/Thinktank_Birmingham_-_object_1889S00044%282%29.jpg?1636095715549
[5] Thomas, J. M.: Michael Faraday and The Royal Institution: The Genius of Man and Place, 1991
[6] Jacobi, M. H.; Stammer, K.: Jacobi, über die Theorie der elektromagnetischen Maschinen, Polytechnisches Journal, Vol. 125, 1852, No. XCV, 438-445
[7] The Illustrated exhibitor and magazine of art, 1852, 295ff
[8] NN.: Ueber Elkington's Fabrik für Galvanoplastik, Polytechnisches Journal, Vol. 170, 1863, No. LXXX, 269-271
[9] NN.: Gramme's magneto-electric machine, Polytechnisches Journal, Vol. 202, 1871, No. LVI, 239-241
[10] Landau, U.: Geschichte(n) der Galvanik - Emil Wohlwill: Ein Mann mit vielen Fähigkeiten, Galvanotechnik 8/2017, 1570-1573