US 2960455 A
Description (OCR text may contain errors)
Nov. 15, 1960 R. P. FRANKENTHAI.v
ELECTROLYTIC CELL Filed July 23, 1958 United States Patent C) ELECTROLYTIC CELL Robert P. Frankenthal, Pittsburgh, Pa., assignor to United States Steel Corporation, a corporation of New Jersey Filed `luly 23, 1958, Ser. No. 750,507
Claims. (Cl. 204-195) This invention relates to an electrolytic cell and, in particular, to a cell adapted for use in determining the thickness of the oxide coating on a specimen of sheet metal.
'It is known to determine the thickness of an oxide coating on a sheet-metal specimen by the time required for the coating to be reduced when the specimen is made cathode in an electrolytic cell. It is the object of my invention to provide a cell adapted to receive and hold a specimen with a predetermined area thereof exposed to an electrolyte. In general terms, my improved cell is a chamber open at one end having means to hold a specimen temporarily over the open end, and hose connections for filling it with electrolyte and draining it when the measurement has been completed.
A complete understanding of the invention may be ob tained from the following detailed description and ex planation which refer to the accompanying drawings illustrating the present preferred embodiment. In the drawings:
Figure 1 is a plan view;
Figure 2 is a vertical longitudinal section taken on the plane of line II-II of Figure l, with parts shown in elevation;
Figure 3 is a transverse section taken along the plane of line III-lll of Figure 2;
Figure 4 is a partial section taken along the plane of line IV-IV of Figure l; and
Figure 5 is a portion of Figure 2 to enlarged scale.
Referring now in detail to lthe drawings, the cell of my invention, indicated generally at 10, is mounted on a base 11 by means of a back panel 12 upstanding thereon. The base and panel are preferably of laminated resin such as Micarta. The cell proper comprises a block 13, conveniently of methyl methacrylate or similar resin, having a horizontal bore 14 extending thereinto from one end and terminating just short of the other end. An opening 15 is formed in the latter.
The first-mentioned end of the bore is counterbored as at 16. A porous disc 17 of fritted glass or the like is seated in the counterbore and held by a sleeve 18 of said resin fitted therein. The counterbored end of the bore 14 is closed by a block 19 of material the same as or similar to that of block 13, secured thereto by screws 20. Block 19 is secured to panel 12 by screws (not shown) and is provided with a gasket 22, an anode 23 in the form of a ydisc of platinum-wire mesh having a diameter substantially equal to that of sleeve 18, a binding post 24 and a conducting strip 25 connecting the anode to the post (see Figure 5)` A closure head 26 adapted to overlie opening 15 is mounted on a rod 27 reciprocable in a guide 28 secured to panel 12. A toggle linkage 29 including a hand lever 30 permits head 26 to be set iirmly against the adjacent end of block 13 or retracted therefrom. Head Z6 has a peripheral sealing gasket 31 and a compressible pad or cushion 32 of foam rubber or the like on its inner face.
By this construction a sheet-metal specimen 33 disposed between the head and opening 15 may be held over the latter temporarily, exposing a predetermined area thereof to an electrolyte 34 filling bore 14 to a level above the top of opening 15. A helical contact spring 35 fitted in a hole 36 in the end of block 13 adjacent opening 15 makes electrical contact with the specimen. A binding post 37 is connected to the spring by being screwed into a plug 38 inserted in the spring (see Figure 4).
Disc 17 serves as a partition defining an anode cornpartment 39 and a cathode compartment 40. The disc is permeable to ions but prevents diffusion of oxidation products from the anode compartment to the cathode compartment. The anode compartment has a filling port 41 and a drain connection 42 including a stop cock and hose. The cathode compartment has a connection 43 to a reservoir of electrolyte and a drain connection 44, both including stop cocks and hose. It also has a port 45 for the introduction of a reference of voltmeter electrode, and a vent 46. inert-gas ports 47 and 48 enter block 13 tangentially of bore 14 and have nipples 49 for hose connections to a suitable source of gas such as ia tank of compressed nitrogen.
In using the apparatus described above, anode compartment 39 is filled through port 41 with an electrolyte such as a 1 millirnolar aqueous solution of hydrobromic acid. Cathode compartment 40 is purged by introducing inert gas through ports 47 and 48. A specimen is placed over opening 15 and clamped against the end of block 13 by head 26. The cathode compartment is then iilled with the same electrolyte from the reservoir by opening the stopcock in connection 43. A current source is then connected across binding posts 24 and 37 to cause a constant current flow through the cell at a density of about 0.3 millampere per square inch of the exposed area of the specimen. During electrolysis, inert gas is introduced through port 48 only.
Determination of the thickness of the oxide coating on the specimen is made in the known manner, i.e., by observing t'he time required to cause a sudden rise in the voltage between the specimen and reference electrode, indicating that all the oxide on the exposed area of the specimen has been reduced. On completion of a determination, electrolyte is drained from compartment 40, the specimen replaced with another and the compartment refilled for the next operation.
The invention provides means for rapidly and accurately determining the thickness of oxide films on sheetmetal specimens. It is sturdy, easy to operate, simple and inexpensive yet it possesses all the refinements necessary for precise results. The wire-mesh anode, being almost the same size as the exposed area of the cathode, insures uniform current distribution over that area.
Although I have disclosed herein the preferred ernbodiment of my invention, I intend to cover as well any change or modification therein which may be made without departing from the spirit and scope of the invention.
l. A cell for electrolyzing a sheet-metal specimen comprising a ver-tical panel, a block secured to said panel having a chamber extending horizontally thereinto from one end thereof, a closure for said end, means slidably mounting said closure on said panel for movement into engagement with the block in a position overlying the chamber at said one end, Ian electrode of sheet material overlying the other end of said chamber, and a terminal on said block having yielding means adapted to be engaged by a sheet-metal specimen held against said one end by said closure.
2. A cell as defined in claim 1, characterized by a Patented Nov. 15, 1960 A2,960,455 Y Y- toggleilinkage'on vsaid panel, said closure being pivoted to said linkage.
3. A cell as dened in claim 1, characterized by said chamber having a porous partition disposed transversely therein between the ends thereof.
4. Acell as `deflnedin claim 1, characterized byY a drain port'in said lblock intersecting said chamber and a pipe connected to said port.
5. A cell for electrolyzing a sheet-metal specimen comprising a chamber having an opening at one end, said end being adapted to receive a specimen laid flatwise thereagainst, a closure head, means mounting said head for movement toward and from said end Veffective to hold a specimen in place over said opening, means on said chamber making electrical contact with a specimen when 'so held in place, a permanent electrode mounted in said References Cited in the le of this patent UNITED STATES PATENTS 2,319,196 Anderson et al May 18, 1943 2,457,234 Herbert let al Dec. 28, 1948 FOREIGN PATENTS 564,516 Great Britain Oct. 2, 1944