US1842541A - Method of and means for the prevention of corrosion - Google Patents

Description

Jan, 26, 11932.. E. CUMBERLAND METHOD OF AND MEANS FOR THE PREVENTION OF CORROSION Filed March 12. 1927 I WE 0/0 W fi 4 F fi ao a H //Vl/E/V 70A U.) Ema/r Camber/ma M4 HQ M 6/5 ATTOR/WWJ Patented (fan 26, 1932 TES PATENT OFFICE ELLIOTT UUMBEJRLAND, F KINGSTUN HILL, ENGLAND METHOD OF AND MEANS FOR THE PREVENTION OF CORROSION Application filed March 12, 1927, Serial No. 174,905, and in Great Britain June 15, 1926.

The general object of this invention relates been found both in the case of marine and to an improved method of and means for the land turbines that stray currents generally prevention of corrosion in metals or metallic of very high potential are set up, the cause in articles which are, or are liable to be imsome cases being the impinging of the steam inersed in, or in contact with liquids capable on the turbine blades and such stray currents of acting as electrolytes. have also been found to cause corrosion.

It is well known that where an electrolyte It has also been found that in many inis in contact with two different metals galstances metallic substances such for example vanic action may occur which results in coras water mains, have been corroded unduly,

w rosion, and the prevention of corrosion for rapidly in the vicinity of electric generating example of ships hulls, stern frames, prostations and I have found that such corropellers, boilers, condensers and the like, both sion is again due to stray currents or leakof the marine and land types, has long been ages from the electric plant.

a difficult problem. It has been generally Now the method above described has been l5 supposed that this corrosion was due entirely found to be unable to protect metallic articles to electro-chemical or galvanic action, such from corrosion due to any of the latter type for example as that which occurs between a of causes and according to the present invenbronze propeller and the steel hull of a ship tion I provide an improved method of and with the sea as an electrolyte, or to difiermeans for protecting metallic substances 2o ences of temperature causing thermo-galagainst corrosion due to causes of this type. vrnic pairs, which may occur in boilers, 0011- According to the invention therefore I prodensers and the like. tect metallic articles from corrosion due to ltn order to prevent this type of corrosio causes of the kind referred to bv arranging l have previously proposed to employ a s pafor all the actual source of corrosion produc- 25 ratesource of electrical energy, suc a ing electric currents or disturbance to be so dynamo and to Connect the Positive P connected to the article or articles tobe prothereof to insulated anodes in the various t t d that; th latter form part of the negaboilers, condensers, stern frames and the like fi d f th i it to be protected whilst the negative pole is con- I th Words I h f d th t th nected to the hull of the ship or to the actual i i f Separate Source, f l t i l part tha is t e p o ergy for rendering the art cles to be protected it was found that where the corroslon W negative is not capable of producing the dedue entirely to causes of the kind referred i d ff t b t th t th protection a only H113 method gave satlsfflctmy lorevenhlve be afforded by the combined effects of all the -T") results but in some Cases which for along tlmfi sources of energ'v would therwise were difiicult to explain the method was found Cause th i h to be unsuccessful. Preferred methods of carrying out my iniits a result of P d experlment I have vention as appli d to certain specific devices now found that in addition to the causes ret t ill now b d ib d bv Way 40 fe l'ed to Such as or in ry galvanic @196" of example onlv. and are illustrated in the tro-chemical action, COI'I'OSlOIl of metals is accnmpanving drawings in frequently due to electro-disturbances or Fig 1 shows i art s ti nal elevation stray currents, leaks the like, Tesllltlng how the invention can be applied to Water from the operatlon of electric or other mai d chmery- Fin". 2 a diagrammatic plan view of the ap- As mstances of such causes I mav mention li ti t a marine tu bi nd condenser by way of example only that in the case of l t ships, corrosion has been found to be due to Referring to Fig. 1 which shows the applileakage from electric plant such for example ti f my i ti n t a ater main in the as a llghtmg and Power Moreover it has vicinity of say an electrical generating stacaused by stray currents passing through the fluid -within the main is thus prevented and in order to prevent external corrosion from the same causes, and in which the damp earth may act substantially as an electrolyte, an anode bar 5 is buried in close proximity to the part of the main where corrosion is taking place and has the positive potential of the generator impressed thereon in a similar manner to that in the case of the internal anode.

As remarked generally below resistances may be used in the leads of the generators, especially when several are used in order that the currents passing to the electrodes of the articles to be protected may be properly adjusted to eifectivelv prevent corrosion. As shown in Fig. 1 the negative lead includes the variable resistance 100 and the positive lead includes the variable resistance 101. The main lighting or power circuit wires leading from the generators are indicated at 50 and 51. As illustrated in Fig. 1, if the leak should occur at X in the positive leg 50 of the main circuit, current would fiow through any conducting path passing from the leak to the article 1 to be protected, and through the wall of the article to the negative'connec tion and back to the generator. Should a leak occur in the negative leg of the circuit no current wiil flow, since the objects are then connected to the negative side of the current source and not through the conducting medium around, and in the article are maintained at the proper positive potential by means of the electrodes 2 and 5. As a result, when the resistances 100 and 101 are properly adjusted no stray currents can leave the articles to be protected in the direction to effect corrosion thereof at the points where currents would otherwise lead.

It will be apparent that the method described can be applied for protecting mains externally, internally. or for both purposes.

Figure 2 shows in diagrammatic plan view the application of my invention to the protection of a condenser 9 from corrosion caused by stray currents from a marine turbine shown at 11, such currents being caused in some cases by steam issuing at high velocity from the turbine nozzles and impinging on the blades causing a difference of potential to be set up, the oil between the rotor shaft and its bearing acting as an insulator between said rotor and the stationary part of the turbine structure. In this case I provide copper gauze or other suitable brushes 6 either directly in contact with the shaft 7 or in contact with collector rings shown at 12 carried thereon and having electrical connection with anodes 8 supported on insulating members 13 wholly or partially submerged within the electrolyte in the condenser 9, the condenser body itself being maintained at negative potential by connection 14 with the turbine casing, alternatively electrical connection may be made between the turbine shaft and the casing or otherwise earthing the lead therefrom. In the case of a ships lighting and power dynamo being the cause of corrosion I run leads if necessary through one or more suitable resistances from the positive pole of said dynamo to the anodes and from the negative pole to the article to be protected.

I have found that in many cases the method herein described will act as a protection against corrosion caused by ordinary electrochemical or galvanic action and in some cases this has even been found to be successful Where the corrosion producing source of electrical energy has only been intermittently in operation, such for example as in .the case of a ships lighting set. This is probably due to the negative polarisation of the article to be protected and the formation of a film of hydrogen thereon which effects have lasted until the set has again been put into operation. It should, however, be noted that where necessary or desirable the present invention may be applied together with previously known protective methods involving the use of separate sources of electrical energy.

This invention may generally be applied to all metallic structures or the like which are or which are liable to be subjected to corrosive action of the types referred to, and which are liable to be immersed in or in contact with liquids capable of acting as electrolytes. Among such articles I may mention for example bridges, reinforced ferro-concrete buildings, fluid conduits, floating docks, gasometers, piers and lock gates in additlon to those examples already given.

In the foregoing I have described by way of example several methods of carying out my invention but it will be ap arent that these can be varied within wide 1m1ts without departing from the scope thereof, the essential feature in each case being that the same source or sources of electrical energy which is or are causing the corrosion are utilized to prevent it by rendering the article or articles to be protected negative to the particular source or sources of electrical energy in question, a'corresponding pos1t1ve pole or plurality thereof being insulated from said article or articles and immersed or partially immersed, in the electrolyte so that current can only flow through such electrolyte in the desired direction.

I claim 1. The method of preventing the destruction of metallic objects in contact with an electrolyte by electrolytic decomposition by electric currents from a current source comprising connecting the negative side of said current source to the object to be protected, providing an electrode adjacent the object to be protected and connecting the electrode to the positive side of said current source.

2. The method of preventin the destruction of hollow metallic objects 5y electrolytic decomposition by electric currents from a current source comprising connecting the negative side of said current source to the object to be protected and connecting the positive side of said current source to electrodes inside of and outside of the object to be protected.

3. Tn an arrangement as described, the combination with a current source of a metallic object to be protected from electrolytic decomposition. said object being in contact with an electrolyte, a connection between the negative side of said current source and said metallic object, an electrode in contact with the electrolyte and a connection between the positive side of said current source and said electrode.

4. Tn an arrangement as described, the combination with a current source of a hollow metallic object to be protected from electrolytic decomposition, said object surrounding an electrolyte and in contact with it, a connection from the negative side of said current source to said object, an electrode supported within said object and insulated therefrom and in contact with the electrolyte, another electrode in contact with the electrolyte and connections from the positive side of said current source to said electrodes.

5. Tn an arrangement as described, a metallic object in contact with a conducting medium, current sources in electrical contact with the electrolyte, a connection from the negative side of each of said sources to said metallic object, an. electrode in contact with the electrolyte and a connection from the positive side of each of said current sources to said electrode.

6. The method of preventing the destruction of metallic objects in contact with an electrolyte by electrolytic decomposition by electric currents from current sources, comprising ascertaining all of the sources of the corrosion producing currents, connecting all of the negative sides thereof to the article to be protected, providing electrodes adjacent the object to be protected and connecting all of the positive sides of the corrosion producingsonrces to said electrodes.

In testimony whereof T have hereunto set my hand this 25th day of Februar 1927.

ELLIOTT CUMBER AND.

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