US 3672963 A
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United States Patent 3,672,963 PROCESS OF COATING METALS WITH MERCURY OR MERCURY AMALGAMS Vito A. De Palma, Tonawanda, N. assignor to Cornell Aeronautical Laboratory, Inc., Buffalo, N.
No Drawing. Filed May 15, 1970, Ser. No. 37,892 Int. Cl. C22d 1/26; C2311 1/00, 5/00 US. Cl. 20414 N 6 Claims ABSTRACT OF THE DISCLOSURE A process for wetting metals wherein, the metal to be coated is electropolished in a substantially alchol bath and is brought in proximity with a Wetting agent; the potential is reversed, causing the wetting agent to adhere to the metal to be coated.
BACKGROUND OF THE INVENTION The present invention relates to a process for coating metals with mercury or mercury amalgams or alloys.
In a copending application entitled, Embrittlement Machining Apparatus, by Paul Rosenthal, and assigned to the assignee of the present invention, apparatus is dis closed to facilitate the machining or cutting of hard-tomachine materials. The apparatus presented in this application requires that an agent be added to the surface layers of the material to be machined which renders these layers brittle and weak so that they can be machined more readily. One such agent used to embrittle stainless steel is mercury. Success of the machining requires that the material to be machined be completely wetted by the embrittling agent. In the case of stainless steel and mercury as the sole wetting agent there has heretofore been no successful wetting process.
SUMMARY OF THE INVENTION The present invention provides a process for thoroughly coating or wetting the surface layer of a metal, such as stainless steel, with a chemical agent, the principal constituent of which may be mercury.
Basically, the process according to the invention comprises the steps of: placing the metal to be wetted in an electrolytic bath having an anode fabricated of a suitable conductor; placing the wetting agent in the bath in close proximity to the metal to be wetted; and applying a voltage potential across the anode and the metal to be wetted whereby the same is uniformly coated by the wetting a cut.
For complete wetting, the material to be coated must be clean, smooth and free of surface impurities. To this end, prior to applying a potential across the anode and metal to be coated, a reverse potential may be applied to electropolish the metal to be coated. This may occur prior to or subsequent to the addition of the wetting agent.
DESCRIPTION OF THE PREFERRED EMBODIMENTS The metal to be wetted is placed into an electrolytic bath forming one of the electrodes thereof. The other electrode is comprised of a suitable conductor which may be a similar metal. The electrode to be wetted must be clean, smooth and free of surface impurities. This cleaning may take place before the electrode is inserted in the bath; however, contamination may be more likely to occur. It is therefore preferred that cleaning take place in the bath. To this end, a voltage potential is applied be- 3,672,963 Patented June 27, 1972 "ice tween the electrode to be cleaned, which now serves as an anode, and the other electrode, which now serves as a cathode, causing the polishing of the anode, as is well known; the exact distance between the cathode and anode is easily determinable in any given situation by those skilled in the art.
The wetting agent is placed in the bath in close proximity to the metal to be wetted. This can take place before or after the electropolishing steps. The potential is reversed so that the electrode to be wetted is now the cathode and the other electrode is now the anode. The reversed potential across the anode and cathode causes the wetting agent to adhere to and uniformly coat the cathode, which is the metal to be coated.
While the exact mechanism whereby the wetting agent adheres to the cathode in response to the potential is not known, it is believed that the electrostatic repulsion between the anode and the wetting agent lowers the surface tension of the wetting agent and drives the same to the cathode.
By way of example and not limitation, stainless steel has been wetted with mercury amalgams as follows:
The stainless steel is made the temporary anode in an electropolishing bath of 94 percent ethyl alcohol and 6 percent perchloric acid, which is cooled to below 20 C. for the polishing operation. The temporary cathode may also be stainless steel or any other conductor. A quantity of mercury or a mercury-zinc amalgam is added to the bath. A potential of about 12 volts DC is applied across the temporary anode and cathode to electropolish the anode. Afterwards the current is reversed and a suitable potential difference of up to 45 volts DC is applied with the stainless steel to be coated now serving as the cathode. When the cathode is brought into proximity with the submerged pool of mercury or mercury amalgam it becomes coated with the mercury or the mercury amalgam.
Alternatively, any other suitable metal such as aluminum and iron can be similarly coated with mercury or mercury amalgam.
Although a preferred embodiment of the present invention has been described, modifications thereof will natural- 1y occur to those skilled in the art. It is therefore intended that the present invention is to be limited only by the scope of the appended claims.
1. A process for uniformly wetting a metal, comprising the steps of:
(A) placing the metal to be wetted as a first electrode in an electrolytic bath, the main constituent of which is alcohol, said bath having a second electrode,
(B) applying a voltage potential between said first electrode and said second electrode for electropolishing said first electrode,
(C) placing mercury or mercury amalgam in said bath in close proximity to said first electrode, and
(D) reversing said voltage potential such that said first electrode serves as a cathode and said second electrode serves as an anode, whereby said first electrode becomes coated with said mercury or mercury amalgam.
2. The process according to claim 1, wherein;
(E) said metal to be wetted comprises a ferromagnetic.
3. The process according to claim 2, wherein;
(F) said ferromagnetic comprises stainless steel.
4. The process according to claim 1, wherein;
(B) said metal to be wetted comprises aluminum.
5. The process according to claim 1, wherein;
3 (B) said bath comprises substantially 94 percent ethyl alcohol and 6 percent perchloric acid. 6. The process according to claim 5, wherein; (F) said voltage potential is less than 45 volts DC.
References Cited UNITED STATES PATENTS 4 FOREIGN PATENTS 1 44/21,'203 1969 Japan 204-45 R 1,049,810 1966 Great Britain 204-45 R 1,031,197 1966 Great Britain 204-181 JOHN H. MACK, Primary Examiner T. TUFRIELLO, AssistantExaminer US. Cl. X.R.