US2458908A - Method of stripping electrodeposited manganese - Google Patents

Description

Patented Jan. 11,1949

METHOD OF STRIPPING ELECTRO- DEPOSITED MANGANESE James H. Jacobs, Boulder City, Nev., assignor, by mesne assignments, to Crimora Research and Development Corporation, Crimora, Va., a corporation of Virginia No Drawing. Application November 13, 1944, Serial No. 563,325

2 Claims. 1

This invention relates to an improved method of treating electrolytic manganese and more par ticularly to heat treatment of such manganese to improve its mechanical and physical properties.

An important aim is to provide a method of heat-treating cathode plates on which manganese has been deposited to facilitate removal of the plated metal from the cathodes.

Other aims and advantages of the invention will appear in the following description of the preferred mode of practicing the method.

According to this invention, the cathode with the manganese deposited thereon, may be dippedv or otherwise covered w th a dichromate solution, for example, a 1% sodium or potassium dichromate solution, and is then washed in water. The purpose of this is to provide a bright surface after a subsequent heating step which will be described.

The cathode, with the manganese deposited thereon, is conveniently passed through an oven in which the temperature is maintained well below the allotropic transition temperature of about 742 C. Preferably, the temperature is maintained at about 350 C. for a substantial period, at least until gas evolution ceases. It has been found that this temperature toughens the metal.

The oven is preferably maintained under a partial vacuum of about 340 mm. of mercury. The plated cathode is allowed to remain in the oven from 15 minutes to 2 hours, depending upon the thickness of the deposited manganese on the cathode.

As an incidental result of the foregoing treatment, the occluded gases in the manganese deposit, particularly hydrogen, are driven off thereby providing a substantially hydrogen-free manganese, which is highly desirable for some commercial purposes, such as the production of highgrade alloys.

Ordinarily, the cathode is formed of metal, such as stainless steel, having a relatively low temperature coeflicient of expansion with respect to manganese. As a result of its being subjected to the heat-treatment, above described, the layer of manganese on the cathode is toughened and is more or less loosened, so much so, that some of it may flake off in the oven. When the oath- 2 ode is removed from the oven, the balance of the manganese is stripped off by either tapping or bending the cathode.

The method may be practiced by placing the cathodes on suitable racks and providing means for conveyingthem into and outer the evacuated oven without breaking the vacuum seal. Furthermore, suitable means may be provided for removing the flaked off portion of the manganese I which collects in the bottom of the oven. The use of an evacuated oven is, however, not absolutely essential to the practice of the invention.

It has been found that, when the electrolytically deposited manganese is subjected to heattreatment, as set forth, any gamma manganese present is transformed to alpha manganese. Moreover, it has been found that the manganese is not readily discolored by exposure to the air during heat-treatment. This is probably due to evolution of some of the occluded gases.

It will be understood that the present invention is not limited to the heat-treatment of manganese deposited on cathodes. It may also be practiced by first stripping the, manganese from the cathodes and then subjecting the stripped manganese to the heat-treatment, as hereinbefore set forth. The principal purpose for such heat-treatment is to toughen the stripped metal and thereby minimize breakage in shipment, as well as to evolve the occluded gases, particularly hydrogen, which are objectionable when the manganese is subsequently used for alloying and other purposes.

' ture of about 350 C. for a period of fifteen minutes to two hours; and then breaking the deposited metal from the cathode plate.

2. That method of stripping electrodeposited manganese from a stainless steel cathode plate which is characterized by heating the plate with the deposited metal to a temperature of about a 350 C. for a period ranging between fifteen minutes and two hours in a partial vacuum; and Number Name Date then breaking the deposited metal from the 2,055,963 Boss Sept. 29, 1936 cathode plate in the form of large flakes. 2,061,759 Eitel et a1 Nov. 24, 1936 JAMES H. JACOBS. 2,325,660 Chamberlain Aug. 3, 1943 5 OTHER REFERENCES REFERENCES CITED Information Circular 6768 of the Bureau of The following references are of record in the Mines May 1934, pp 3 to 7 file Qf this patent Steel, vol. 105, Oct. 30, 1939, pp. 43-45.

UNITED STATES PATENTS 10 Metal Industry, Mar. 22, 1940, pp. 273, 274. Number I (Name w Transactions of thekfiamday Society, vol. 19

1,803,691 Brockway May 5, 1931 (1924), page