US661165A - Protecting underground metallic structures from effects of electrolysis. - Google Patents

Description

No. BBL-I65. Patented Nov. 6, [900. L. I. BLAKE.

PROTECTING UNDERGROUND METALLIC STRUCTURES FROM EFFECTS OF ELECTROLYSIS.

(Application filed Aug. 9, 1900.)

(No Model.)

"m: NORRIS PETERS co. PHOTQLITHQ, wAsnmcmu. v.1:v

UNITED PATENT Cr tics.

LUOIEN I. BLAKE, OE LAWRENCE, KANSAS.

PROTECTlNG UNDERGROUND METALLIC STRUCTURES FROM EFFECTS OF ELECTROLYSIS.

CTEJEFZGATION forming part of Letters Patent No. 661,1 65, dated November 6, 1900.

Application filed August 9, 1900. Serial No. 2 ,436. N0

To all whom, it may concern.-

Be it known that I, LUoIENl. BLAKE, a citizen of the United States, residing at Lawsuch, for example, as is extensively used for carrying water, gas, steam, &c.-and other metallic structures embedded in the soil are subject to destructive corrosion resulting from the electrolytic action of direct electric currents which, traversing such structures, leak off from the same into the surrounding earth. Attempts have been made heretofore to prevent these destructive effects of electrolysis by covering the exposed metallic surfaces with insulating material, so that the currents may be confined to the structures and not escape directly into the earth, or by connecting metallic conductors at intervals to the structures and establishing good connections therefrom to provide easier paths than the earth for the currents to follow; but with the present great development of electrical systems, particularly railroads, the problem of protecting underground pipes and other structures from electrolytic corrosion due to leakage or stray currents has become so seriousthat it has even been proposed to make water and gas pipes of glass, porcelain,or other insulating material. In all cases, however, the remedy proposed has involved either the insulation of the structures or the use of special conductors for leading the currents from the structures to earth or back to their sources, and so far as I am aware these provisions have been only partially successful.

Electrolytic corrosion of an underground pipe or other structure is confined to those points where the electric currents leave the metallic surfaces and pass into and through the surrounding earthy material. The effects of the escaping currents are manifested by a transporting away of the metallic material into the earth and the formation of metallic compounds, both of which actions inj uriously affect the metal structure. This so-called electrolytic corrosion, however, is not a pril l l i model.)

mary effectof the escaping current, bu t-dueto a secondary action chemical in its nature.

It iswell known that when a direct current passes through a solution a portion of the lat-- ter is decomposed, and the products which severally appear at the electrodes by which the current enters and leaves the solution are capable of chemically combining with the material of the electrodes if that material is susceptible to such combination. 'lhese chemical combinations, therefore, are secondary effects of the current.

In cases where electrolytic corrosion of underground metallic structures has occurred I have proved by investigation and direct ex.- periment that the current has decomposed solutions present in the soil, not-ably the chlorids and sulfates, and that the products thus set free have attacked the metalsurfaces and produced the well-known electrolytic effects.

It is well known that a current which leaves a metallic surface by a conducting path which is non-ionizable or not chemically decomposible will produce no electrolytic effect on that surface, and I have taken ad vantage of this fact in carrying out my plan of protecting underground metallic structures against electrolytic corrosion by inter-posing between the metallic surfaces and the surrounding soil an electrically-conducting me dium which is non-ionizable and which will prevent access to such surfaces of the products of electrodecomposition of any solutions which may be present in the soil. The protective medium may be composed of one or more of a large number of materials and maybe applied in many ways. I may, for example, employ carbon in any suitable form, preferably a mixture of graphite with some binding material by means of which it may be applied and fixed to the surface of the metallic structure which it is designed to protect. I have found, for example, that a conductive mixture of graphite and paraffin is well adapted for this purpose.

It is not essential that the substance of the protective medium should be itself a conductor of electricity, provided only it permit the passage through it when applied for use of the current while preventing the access to the metal surface of the products of decomposi- IOO iion. Such substances are now and have been eu'tployed as tum-porous electrolytic diaphragms in galvanic batteries and electrodecomposition-cells. Among such substances maybe mentioned precipitated chalk, pulverized anthracite coal, gelatinized C0111- pounds of silica, and the like, which when. used in layers of sut'ficient thickness and moistened, it by nature they are dry, permit I the ready passage of a current, but prevent the recombination ofthe products of electrodecomposition.

The 11 rotective medium may be applied to the metallic structures in any convenient manner. It may be applied in a thin layer with brushes or suitable tools, or it may be deposited in larger amounts in a trench and the metal structure embedded in it.

The coating of metallic structures where exposed to the soil with a cont'lucting' substance will enormously increase the drainage of any electric currents from these SYI'UOMH'GS by providing innumerable points of exit, thereby relieving these strt'tctures of currents which are harmful particularly at the joints. Such use of a conducting-coating, moreover, clearly the direct opposite in its nature to the means heretofore employed for similar purposes.

In the accompanying drawings, Figure 1 I well known I represents in longitudinal section a water or gas main A with a protective coating l3. Fig. 2 represents in cross-section an iron beam A embedded in a protective main B.

Having; now described my invention, what I claim is- 1. As a means of protecting an underground metallic structure from corrosion resulting from electrolytic action, a conduct:- ing-coating applied thereto, which is unaffected by electrolytic action and impervious to the products of such action, as set. forth.

2. The combination with an nntileruround metallic structure of an electrically-(amiducting' medium snrroutnline' the same, which is unaffected by electrolytic action and impervious to the products of such action.

3. The C(H'llhlllztlltjil with an umleru'rountil metallic structure of a coating composed of a non-ionizalile conductor and a binding n1aterial impervious to fluids, as set forth.

4. The combination with an uiulcrground metallic structure of a conductive-coating compound of powdered graphite and para ttin, as set forth.

LUCIEN l. BLAKE.

\Vitn esses:

J. CONVERSE GRAY, H. W. BIGELOW.

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