US1862745A - Process for electrodepositing iron - Google Patents

Description

PROCESS FOR ELECTRODEPOSITING IRON Filed Dec. 12, 1928 @wiow Patented June 14, 1932 UNITED STATES PATENT OFFICE GEORGE PRESCOTT FULLER, OF NIAGARA FALLS, NEW YORK, AND CEDRIC A. VINCENT DAVISS, F NIAGARA FALLS, ONTARIO, CANADA, ASSIGNORS, BY MESNE ASSIGN- MENTS, OF ONE-HALF T0 SAID FULLER AND ONE-HALF TO EDWARD MICHAEL, 0F

BUFFALO, NEW YORK.

PROCESS FOR ELECTRODEI'OSITING IRON I Application filed December 12, 1928. Serial'No. 325,499.

This invention relates to improvements in a process for the electrolytic production of iron tubes.

Processes for the production of seamless iron tubes by electrodeposition have long been known and attempts been made to put such processes into commercial operation but without success because the cost of production was too high.

The object of the present invention is to provide an electrolytic process for the pro-- duction of such tubes which is more efficient and economical than the processes heretofore employed so that tubes made by this process can be sold at prices which the market will pay.

The invention consists in the features, steps of operation and details which will first be described in connection with the accompanying drawing and then more particularly pointed out.

In the drawing- Figure 1 is a diagrammatic view illustrating in a general way a plant suitable for car- 2 rying out the process in a continuous or cyclic manner.

Figure 2 is a horizontal section of one of the electrolytic tanks;

Figure 3 is a cross section ofthe sameon 3 the line 33 of Figure 1 and Figure 4 is an elevation of one of the semipartitions.

An electrolytic cell A of any suitable character capable of containing a solution of electrolyte from the top of the sides of which cell are suspended in the electrolyte in the cell, as by hooks, two anodes B, of graphite, since that material is a conductor and is also insoluble. These anodes'may be treated with molten sulphur -or other suitable imp-regnating material to prevent disintegration, if desired. Cell A is also arranged to support within it a cathode'C, which is also used as a mandrel on which the iron tube is to be formed.

Cathode C is made of high carbon steel, ground and polished so it will be true and smooth. This cathode or mandrel is required to rotate at a comparatively high speed during the electroplating operation and it is therefore advantageous to have it balanced and located substantially centrally in the cell equidistant from the two anodes B. It is mounted also to be easily removed and replaced. v

Cell A, which may be of concrete or other suitable material, is provided with a cover D to protect it from injury, prevent loss of heat and reduce the access of air to the electrolyte therein. The electrolyte is fed to the cell from any suitable supply tank E.

Cell A has one compartment for the mandrel, anodes and electrolyte, that is, no dia phragm is employed. Also the cell is provided a short distance from each end, with semi-partitions F, F. The central portion of each partition is substantially of V-form. When partitions F, F are of concrete, it will be advantageous to have suitably supported in grooves therein, fittings of wood or other suitable material, which when their upper and lower parts are in position, form a circular opening to allow such fittings to act as bearings for supporting the journals G, G of cathode C. Bearings are thus provided 75 which allow of the cathode being easily removed and replaced. Owing to the fact that by this process the necessity for a diaphragm is avoided, all the difliculties heretofore encountered in such diaphragms are avoided.

Partitions F, F do not extend the full height of the sides of cell A but are somewhat shorter than such sides in order that the electrolyte flowing through the cell may have a substantially free flow over their tops and also to temporarily retard its flow at that oint.

Cathode C before being placed in the electrolytic cell is thinly and uniformly coated in any suitable manner with an aqueous suspension of graphite or similar material to form a parting coating, that is a coating which when the tube has been formed is interposed between the mandrel and the tube and thereby allows the tube to be removed easily and without the necessity of using heat for that purpose. After the graphite coating has been applied to the mandrel, a thin coating of iron is then electrode osited upon the graphite coating of the man rel at a low 100 current density. This is done preferably in a separate cell. The mandrel is then mounted in position in the electrolytic cell A, with its journals resting in their bearings and substantially equidistant from the anodes.

The peripheral speed of the mandrel is controlled by the density of current used, which it is advantageous to have high for the attainment of satisfactory results.

Although the preplating of the mandrel with iron at low current density is a great advantage, it may be dispensed with where the current density during the main plating operation is relatively low, that is, where the current is not over 60 amperes per square foot. Such preplating may also be dispensed with where a hard mandrel is used.

Such preplating is advantageous, however,

in any case, as it removes differences of potential on the cathode surface, which cause irregular deposits. These differences of potential are due to variations in the parting material and to impurities and imperfections in the surface of the cathode.

By preplating at a low current density a homogeneous deposit of iron is obtained. \Vith this it is also advantageous to introduce the cathode thus prepared into the cell, and rotate it for a few moments before applying current, with the result that the slightly acid electrolyte dissolves a thin film from the iron coating thus removing any remaining inequality and furnishing a surface free of potential differences. lVhen potential differences exist at the cathode surface, hydrogen is liable to be deposited which causes gas pits or growths, this action being accentuated at high current densities. However, when treated as described, current densities far in excess of those heretofore possible may be employed.

The electrolyte of the present process consists of a substantially saturated hot solution of a ferrous salt, as ferrous chloride, which is maintained at a ten'iperature of above 80 C. and must be substantially free of suspended matter, such as oxides of iron, and, as fed to the electrolytic cell, must be entirely free of ferrous hydroxide. Also, it must contain a trace of iron in ferric form but not to exceed 0.5 gram per litre. This electrolyte may be made in feed tank E, or outside the system and introduced therein as desired.

The electrolyte is caused to circulate in a continuous cycle and at a rate which is controlled by the density of the electric current employed, but the rate of circulation must be such that the maximum content of iron in ferric form in the electrolyte while in the electrolytic cell does not exceed 2.5%

i of the total iron content.

We have discovered that to obtain an acceptable deposit of the iron, it is essential that a trace of ferric chloride be left in the as ferric iron. This prevents the formation of ferrous hydroxide, which we have found to be very objectionable when working for the production of perfect commercial seamless tubing, as such ferrous-hydroxide has a tendency to cause a deposit of hydrogen on the cathode. The chief objection to the ferrous hydroxide is that it forms gas pits or growths, leading to a resulting irregular deposit of the iron.

While it is practicable to remove this objectionable ferrous hydroxide either by oxidation or filtration, we have found that the oxidation treatmentcauses complications in the process and also it is diflicult to regulate such treatment. In treatment by filtration also, ferrous hydroxide may be formed by hydrolysis after filtering if the solution is completely neutral.

In our process neutralization conditions are so regulated that the formation of this objectionable ferrous hydroxide is prevented and, furthermore, we have found that the deposit of the iron on the mandrel is irregular when the ferric iron in the electrolyte exceeds 2.5% of the total iron. Excess of ferric iron is prevented by adjusting the rate of circulation so that the effluent electrolyte is kept at or below 2.5% of the total iron content.

In neutralization it is therefore desirable to reduce the ferric iron to the lowest possible pOintwithout reaching neutrality, as the more ferric iron is contained in the electrolyte, the more rapid must be the circulation in order to remove it before the high limit has been reached.

Since it is desirable that suspend-ed matter in the electrolyte be kept at a minimum, it is usual to employ filtration to this end. In the present process, however, such sus pended matter is satisfactorily taken care of ordinarily by settling, thereby dispensing with the necessity of special filtration.

In existing processes suspended matter is derived from the anodes, from the iron in the neutralizers, or from hydrolysis of thesolution. In the present process, however, through the use of insoluble anodes that source is eliminated and the effect of hydrolysis is minimized, thus limiting the possibility of suspended matter to but one source, namely, the iron in the neutralizers or leaching tanks H, H.

The leaching tanks H and H are filled with iron in metallic form. Although it is most advantageous to use scrap iron for this purpose, it may be from other suitable sources as ore, or iron in metallic form in other combinations soluble in ferric chloride; or it may be soluble iron from any other source which will neutralize the acidity of the effluent electrolyte. It is in these tanks that the heat is adjusted, that is, the heating coils are arranged to restore the electrolyte to the necessary C. or over. Another function of these leaching tanks is the restoring to proper concentration of the iron which was removed in the cell before it is-returned to the electrolyte feed tank E by leaching through the iron therein.

These tanks may be heated from any suitable source of supply, as from a steam boiler, through steam coils J suitably arranged in the tanks for that purpose. The leaching tanks H, H and feed or supply tank E are each provided with a draw-oil pipe and equipped with ayalve to allow sediment to be drawn off when necessary. This sediment may then be treated for recovering anyvaluable contents, if desired.

The efliuent or spent electrolyte is caused.

to circulate through tanks H, H. It will be found advantageous in order to ensure its being restored to normal, that the electrolyte be caused to flow through both tanks H and H, as shown, after having been used in, and discharged from, the electrolytic cell A, either directly'or indirectly. If but one cell be used, the electrolyte will be discharged from supply tank E into cell A, but if more than one cell be used, as is usual in commercial apparatus, the electrolyte will, for better distribution, be through trough I. The

spent electrolyte may also be distributed.

through a trough J and pipe K into the bottom of tank H, thence upward in tank H and out through the overflow pipe L from the upper end of tank H into the bottom of tank H. From this tank H the electrolyte is Withdrawn by a pump of any suitable character, as the rotary pump M shown, and pumped back into electrolyte supply or feed tank E ready for re-useand completing the cycle.

The electric current required may be provided by any suitable source of direct electric current, the negative terminal R forming the cathode connection and the positive collector R forming the connection for the anodes.

While any suitable source of power to rotate the cathode may be employed, that used for illustration herein has been found satis-* factory. It consists of a shaft 0 driven by a motor 0' directly connected thereto inany suitable manner. Shaft O is in turn secured to the journal of -cathode or mandrel C at a point outside of cell A by split coupling P.

An example of a typical run of the process is as follows: N

A concentration of 240 grams per litre of iron in the form of ferrous chloride was used with 0.5 gram per litre as ferric chloride, a temperature of 82 C. being maintained. The peripheral speed of the cathode was 520 feet per minute and the rate of flow of the electrolyte was 9 gallons per minute per square foot of cathode surface. A current density of 125 amperes per square foot was employed, the electrolyte from the cell being maintained at 4 grams per litre of iron in ferric form. Scrap iron was used to neutralize the solution, and no filtration was employed.

This process enables the production of perfect commercial tubes at low cost through the use of cheap raw material. Control of the deposit is attained through the employment of very high current densities, with a higher proportion of good deposits, and a lower content of impurities, especially car bon, in the resulting iron. In addition, the process is very simple.

What is claimed is:

1. The process of electro-depositing seamless iron tubes on a rotatable cathode located in a one-compartment electrolytic cell pro vided with insoluble anodes, which consists in iron compound soluble in ferric salt so that the ferric iron shall not exceed .5 gram per litre, and returning the electrolyte to the cell.

2. The process of producing seamless iron tubes consisting in continuously circulating a substantially saturated hot solution of ferrous salt containing a trace of ferric salt in an electrolytic cell in which is rotatably and removably mounted between insoluble anodes a cathode capacitated to currents of high density, controlling the rate of circulation in proportion to the density of the current so that the ferric iron in theelectrolyte in the cell shall not'exceed 2.5%of the iron content, reconcentrating the effluent electrolyte with iron or iron compound soluble in ferric salt so that the ferric iron shall not exceed .5 gram per litre, and returning the electrolyte to the cell.

3. The process of producing seamless iron tubes consisting in continuously circulating a substantially saturated hot solution of ferrous salt containing a trace of ferric salt in an electrolytic cell in which is rotatably and removably mounted between insoluble anodes a cathode capacitated to currents of high density, depositing a parting plane on said cathode, depositing a film of iron on said parting plane by a current of low density, depositing iron upon said film by a current of high density, controlling therate of circulation in proportion to the density of the current so that the ferric iron in the electrolyte in the cell shall not exceed 2.5% of the iron content, reconcentrating the eflluent electrolyte with iron or iron compounds soluble in ferric salt so that the ferric iron shall not exceed .5 gram per litre, and returning the electrolyte to the cell.

4. The process of depositing seamless iron tubes on a rotatable cathode in a one compartment electrolytic cell which consists in depositing a parting plane on said cathode,

continuously circulating a substantially saturated hot solution of ferrous salt containing a trace of ferric salt, electrolytically depositing a film of iron on said parting,plane at low current density, rotating said pretreated cathode in the electrolyte before the application of current, electrolytically depositing iron upon said film by \a current of high density, controlling the rate of circulation of the electrolyte in proportion to the density of the current supplied to the anodes so that the ferric iron in the electrolyte in the cell shall not exceed 2.5% of the iron content, treating the eflluent electrolyte in a leaching tank with iron soluble in ferric salt to reconcentrate it until the content of iron in ferric form is below .5 gram per litre adjusting temperature to above C., and returning the restored electrolyte to the cell.

5'. The process for the industrial manufacture of electrolytic iron which consists in preparing an electrolytic solution of soluble ferrous salts, said solution being substantial 1y free from ferrous hydroxideand containing ferric iron inan amount not exceeding 2 of the total iron content and not less than 0.5 gram per liter of the bath, electrolyzing said solution by means of insoluble electrodes, and circulating said solution around and past said electrodes at a relatively high speed.

In testimony whereof, I have hereunto set my hand.

GEORGE PRESCOTT FULLER. In testimony whereof, I have hereunto set my hand.

CEDRIC A. VINCENT DAVISS.

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