US1369271A - Cleaning of metallic surfaces - Google Patents

Description

T A. EDISON.

CLEANING 0F METALLIC SURFACES.

APPLICATION FILED JULY 3. 1919.

1,869,271, Patented Feb. 22, 1921 UNITED STATES PATENT orr cs.

THOMAS A. EDISON, 0F LLEWEIIILYN PARK, WEST ORANGE, NEW J ER SEY.

CLEANING or METALLIC soaraons.

Specification of Letters Patent. 7 Patented Feb, 22, 1921.

Application filed July 3, 1919. Serial No. 308,379.,

To all whom it may comic-1w. Be it known that I, Tuonns A. EDISON, a citizen of the United States, and a resident of Llewellyn Park, \Vest Orange, Essex county, New Jersey, have invented certain new and useful Improvements in Cleaningof Metallic Surfaces, of which the following is a description.

Hy-invention relates to the cleaning of metallic surfaces and more particularly to the cleaning of the surfaces of metallic objects electrolytically preliminary to subsequent treatment by which the surfaces so cleaned are coated with another metal or material, as, for example, in processes of electro-plating, amalgamating. tiuniug. galvanizing, enameling, etc., or in the process of coating such a surface with a thin layer or film of a selenide as described in my copending application Serial No. 305,821, filed June 21, 1919, and entitled Electro-plating.

Heretofore, in cleaning the surfaces of metallic objects electrolytically, it has been customary to employ an electrolytic cell comprising electrolyte such as a solution of caustic soda, caustic potash or the like, an anode composed of a suitable material which will not dissolve in the electrolyte, and the metal to be cleaned opposed .to said anode in the electrolyte as a cathode. With the use of such an electrolytic cleaning solution, however, it often happens that the dirtis not completely removed from the cathode, that is, the metal to be cleaned,- and moreover, a black deposit is usually formed on the cathode, probably due to the presence of more or less foreign material in the caustic soda orcaustic potash, as it is impossible to obtain the latter in a pure state.

The principal object of my invention is to provide an improved electrolytic cell including an improved electrolyte therefor, whereby metallic surfaces may be quickly and completely cleaned electrolytically, and whereby no deposit of foreign material will be formed on the surfaces so cleaned.

My invention also resides in an improved process for cleaningmetallic surfaces electrolytically. v I

I have discovered that the foregomg results may-be obtained upon the passage of a current of sufiicient density through an electrolytic cell comprising an electrolyte consisting of a slightly alkaline and nearly saturated solution of a metal of the alkali.

of the metal to be cleaned andopposed to the' anode 3 in the electrolyte 2. The anode 8 and the cathode 4 are respectively suitably supported, as by means of heavy clamps 5 formed of conducting material, from a pair.

of bars 6 and 7 of conducting material carried by the tank 1. A pair of conductors 8 and 9, respectively connected with the anode and cathode, serve to supply the cell with current from any suitable source (not shown).

. The electrolyte 2 preferably consists of a nearly saturated solution of either sodium sulfate or potassium sulphate rendered slightly alkaline by the addition of a s'uf- -ficient amount of a hydroxid of a metal of thealkali group, preferably caustic potash or caustic soda; and when such an electrolyte is employed, the anode is preferably formed of pure carbon, such as graphite, which is only slightly attacked by electrolysis in the electrolytic solution. 'I find that graphite -is preferable over other forms of carbon, owing to its insolubility in an alkaline solution when subjected to electrolysis.

In order to effect the cleaning of the surface of the cathode 4 consisting of the metal to be cleaned, a current equivalent to about 150 amperes per square foot of such surface is passed through the cell. The passage of this current results in the evolution of the alkali metal and simultaneously, due to the decomposition of the water in the electrolyte, in the evolution or generation of'great quantities of hydrogen gas on the surface of the cathode. This hydrogen gas in detaching itself from the cathode mechanically strips off or detaches the foreign matter so as to leave an absolutely clean surface. This result is facilitated by reason of the fact that oil, grease, dirt and other forelgn material are more or less porous so that the gas has an opportunity of forcibly detach- I: stantially as described."

ing itself from the surface to carry the foreign material with it. This action is almost entirely mechanical, though the oil and.

grease are eventually decomposed to a great extent by the alkali. The nascent potassium or sodium evolved. in the cell, primarily on the cathode, also reduces any oxid of the metal of which the cathode is formed and which may. be present on such cathode, to metal. i

lVhen a current of the density above mentioned is passed through the cell, all grease and other dirt and impurities are completely removed from the surface of the metal to be cleaned, that is, from the cathode 4, in from washed, after which it is ready for subsequent treatment, for example, the application thereto of a coating such as a film consisting of a selenide, which may be formed thereon in the manner described in my application above referred to.

Having now described my invention, what I claim as new and desire to protect by Letters Patent of the United States is as follows cell adapted to be employed for cleaning metals, comprising an alkaline solution of a sulfate of a metal of the alkali group, substantially as described.

2. An electrolyte for use in an electrolytic cell adapted to be employed for cleaning metals, comprising a solution of a sulfate of a metal of the alkali group and a. hy-

lVhere a cell droxid of a metal of the alkali group, sub- 3. An electrolyte for use in an electrolytic cell-adapted to be employed for cleaning metals, comprising a solution of a sulfate of a metal of the alkali group and a hydroxid of potassium or sodium, substantially as described.

4. An electrolyte for use in an electrolytic cell adapted to be employed for cleaning metals, comprising a nearly saturated solu-- tion of a sulfate'of a metal of the alkali group-containing an amount of a hydroxid of a metal of the alkali group suflicient ,to render the same slightly alkaline, substantially as described.

5. An electrolytic cell for cleaning metals, comprising an electrolyte consisting of a solution of a sulfate of a metal of the alkali group, an anode formed of graphite, and a cathode consisting of the metal to be cleaned, substantially as described.

-6. The method of cleaning a metal electrolytically, which consists in employing the metal to be cleaned as a cathode opposed to a suitable anode in an electrolyte consisting of an alkaline solution of a sulfate of a metal of the alkali group, and passing through the electrolytic cell a current equivalent to approximately 150 amperes per square footvof the surface to be cleaned, substantially as described.

7. The method of cleaning a metal electrolytically, which consists in employing the suitable anode in an electrolyte consisting of an alkaline solution of a sulfate of a metal 1. An electrolyte for use in an electrolytic of the alkali group, and passing through the electrolytic cell for a period of from approximately'l to 5 minutes a current'equivalent to approximately 150 amperes per square foot of thesurface to be cleaned, substantially as described.

'on signed this 24th day of

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