US1600355A - Coating metal pipe with metal - Google Patents

Description

Sept. 21 1926.

' 1,600,355 S. OTIS ET AL COATING METAL PIPE WITH METAL Filed March 19, 1925 Patented Sept. 21, 1926.

A UNITED STATES PATENT'OFFICE.

SPENCER OTIS AND WILSON T. HERREN, BARRINGTON, ILLINOIS, ASSIGNORS TO NATIONAL BOILER WASHING COMPANY OF ILLINOIS, OE CHICAGO, ILLINOIS, A CORPORATION 01 ILLINOIS.

COATING METAL PIPE WITH METAL.

- Application filed March 19, 1925. Serial No. 16.610.

Our invention has been developed in consolution is thus. constantly brought into connection with. the coating of steel pipe for tact with the interior of the pipe, thus hasprotecting it against corrosion and is partening the action thereof on the ipe and ticularly applicable to coating such plpe quickly removing from the interi r of the 6 with lead. It will be apparent, however, pipe by the flow of the liquid any scale from the more detailed description below, or the like which becomes detached. At

I .that in certain of its features it is applicathe same time the exterior surface of the 60 ble to the coating of other articles than pipe pipe is subjected to the pickling action of and in connection with other coatings than the bath.

10 lead. Thus it is equally applicable to coat- After the pickling is completed the pipe is ing pipe with tin. removed from the pickling-bath and pref- By our improved process we are able to erably. is mechanically cleaned to remove the 66 secure firm, dense, adherent coatings subloosened scale. It is next dipped for a minstantiall free from the imperfections, such ute or two in a bath of sulphate of copper 16 as pin oles and areas of poor adhesion, from which it receives a very light coating which have heretofore been largely responor flash of copper. Other salts of'copper sible for the limited use which has been in which the metal is readily replaced by iron made of coated steel pipe. may be used in place of the sulphate and One' of the features of our improved procthe strength of the solution in any event 2 ess relates to the preparationof the pipe to is made such as to give a light coat of metal receive the coating, and the other to the coatin the course of 'a short treatment. Almost ing process proper and more particularly to any ordinary strength of solution of the the coating of the inside of the pipe. copper sulphate will answer, thou h the The first step in the preparation of the greater the dilution the longer mustt e pipe 25 pipe for coating is the ordinary one of tumremain therein to secure a coating. A solubling, by which much of the loosely attion of per cent is satisfactory. If pretached scale and other adherent matter is ferred the copper may be deposited lec B0 removed. The pipe is next immersed in a trolytically by a known or approved method. hot solution of caustic soda and alternately It aids in securing a satisfactory coating to so made the anode and cathode of an electric pass a current through the pipe or other circuit traversed by a strong current. Any article to be plated and the bath with the ordinary source of current which will give article as the anode for a few minutes to a fairly high current density may be used free it of gas and this is so whether the and connected to the pipe and to iron elecchemical or the electrolytic method of coat- 35 trodes also immersed in the bath, provision ing is employed.

being made for the reversal of current re- After the pipe has been thus treated to referred to above. Preferably the current is move scale, etc., and apply a light copper reversed a number of times before it is cut coating thereto it ma if desired, be given olf and the pipe removed from the bath. its lead coating by dipping in the latter The reversal of current in this manner and metal after being heated in a hot flux, and

theuse of the hot caustic soda solution greatthen drained and quenched in oil. Prefly assist in loosening the scale and removing erably, however, it is treated b the fol any grease adhering to the pipe. The pipe lowing method forming a part 0 the presare next connected to a common header by ent invention. Each length of pipe to be rubber piping or the like and then immersed coated receives in its interior a lead anode in a sulphuric acid solution which may be of substantially the same length which is of 17 per cent acid'strength and is preferasuitably spaced or held away from contact 1 bly kept at about 200 degrees F. temperawith the pipe by rubber disks or spreaders ture. The header is connected to a pum applied thereto at suitable points. The so the inlet of which connects to the bath so that anodes each consist of a small copper core the pickling solution may be pumped surrounded by a layer or coating of the through the inside of each pipe during the metal to be deposited. Thus if the pipe is to I entire time that it is in the pickle. Fresh be lined with lead the anode in each case I Obviously,

consists of a copper core surrounded by a layer or body of lead. We-have found that for the smaller size pipe such as those 1 to 2 inches in diameter we may use an anode the core of which is a 7 inch copper rod and which is surrounded by a lead pipe the outside diameter of-which is about inch. It is desirable to prevent the penetration of liquid between the pi e and core and this may be accomplishe y soldering or swaging the pipe at its ends to or against the copper core.

The pipe provided with the interior anodes as described is next immersed in an electrolytic bath for plating. We have found the wellknown fluoboric lead bath consist of 24: ounces hydrofluoric acid, 12 ounces boric acid and 16 ounces lead carbonate to the gallon of water. satisfactory for this purpose. Lead anodes are distributed at suitable intervals along the outside of the pipe, but at a suitable distance therefrom, or if, as we prefer, a rack ofpipes is treated at once, along the latter, and the pipe are connected as cathodes to a suitable source of current, the anodes, both exterior and interior, also being properly connected to the source of current. As the interior anodes are so much nearer the pipe constituting the cathodes than the exterior anodes can well be'placed, provision must be made for proper distribution of the current between the respective sets of anodes and this is preferably done by introducing suitable resistance in that branch of the circuit which includes the interior anodes.

current could be used for the interior and exterior anodes in orderto secure the proper distribution. If too dense, a current is used the lead deposited is loose and spongy in character. We have found a suitable current density to be from to 1 ampere per square foot. Manifestly the distance between the interior anode and the pipe surrounding it determines the voltage which is permissible between the anodes and the pipes and this distance, with anodes of the same size, depends upon the interior diameter of the pipe. Preferably the exterior anodes are also made with cores of copper or other metal of high conductivity.

In using the interior anodes the source of current is connected to the copper cores the metal of which has a high specific conductivity because of which conductivity there is no substantial drop in current distribution along the length of the anodes, and a very even coating may be produced throughout. The copper cores also give greater rigidity to the anodes. We have described the electrical connections as being such as to make the pipe to be coated the cathode and in any event this is true during the plating operation proper.

vtion to receive the coating,

it drives fi gases occluded or mechanically trapped in or on the surface of the pipe and if desired, different sources of' Preferably. however, we provide means for reversing the current, and at the outset the current is passed through from the pipe as anodes for a few minutes, which puts the pipe in much better condidoubtless because of other adherent matter. referable to coat the outside of the pipe wit lead and the interior with tin. This may be done in separate steps, using substantially the process described above for the outer coating and a similar process with copper cored tin anodes and a suitable electrolyte for the inner coating. Preferably, however, the two steps are done in the same operation in a bath of the described fluoboric lead solution with the exterior lead anodes but with tin interior anodes, preferably copper cored. In this case there is a small but unobjectionable also tends to free it In some cases it'is amount of lead in the inner coating, mainly in the layer next the'metal of the pipe. In the drawing accompanying and formmg apart of this application is shown diagrammatically an apparatus suitable for practicing our improved process. In said drawing Figure 1 is a plan view of the.

apparatus; Fig. 2 a vertical longitudinal section thereof; Fig. 3 a longitudinal axial section of a pipe with our improved anode in place therein and in condition for treatment in the electrolytic plating apparatus, and Fig. 4 is a cross-section thereof.

In Figs. 1 and 2 the vat in which the pipe are submitted to the action of the caustic alkali and electric current is shown at A,

the pipe being cleaned 'at '5, the racks on which they are supported at 6. The pipes are shown as connected by wire 7 to an electric generator 8 to which are also connected electrodes 9 immersed in the bath. A reversing switch 10 is interposed in the connections to the generator for the purpose of reversing the current as above described.

The acid vat is shown at B and the pipes 5 which are transferred thereto in the 11fting racks 6 are connected to headers 11. The latter are connected to the discharge side of a centrifugal pump 12, the inlet side of which is connected by a line 13 to the vat, preferably at the far end of the pipes so that the liquid of the bath may be confirm-- are used for treating alternate racks of pipe,-

respectively, coming from the copper vat. In these vats the pipes 5 in their racks are immersed in the electrolyte previously de-' scribed after the anodes 15 have been inserted therein. The external anodes 16 are arranged at suitable intervals alongside the racks of pipe and both sets of anodes are connected to a generator or generators 20 of electric current to the other terminals of which the pipes being coated Referring to Figs. 3 and 4, the pipe to be coated.is shown at 5 and the electrode 15 located therein is composed of a core 16 of copper and a surrounding layer 17 of the leader other metal to be plated.- The end 18 of the copper core extends beyond the pipe and beyond the coating metal and is adapted for connection to the electric generator. The core is spaced from the interior of the pipe by the spacers or spreaders 18 which preferably are cut from fibre board or the like. It is to be noted that these spacers touch the pipe only over small areas and in order to avoid too thin a coating at the areas of contact the spacers may be moved slightly in the course of the treatment of the pipe.

e claim:

1. A process for cleaning ferrous articles for the deposition of metal thereon which consists in immersing the articles in a bath containing a caustic alkali and passin an electric current through the article and ath.

2. A process of preparin an article of ferrous metal for coating w ich consists in immersing it in a solution of caustic alkali sists in immersing it in a solution of a caustic alkali and passing an electric current and passing through said article and bath alternately in opposite directions.

4. A process of preparing a metal article for coating with metal which consists in immersing it in an electrolyte and passing an electric current through the article and electrolyte alternately in opposite directions.

5. A process of preparing an article of ferrous metal for coating with another metal which consists in immersing the article in a solution of a caustic alkali, passing an electric current through the article and solution with the article as the anode ing the surface of the article with an acid solution.

- 6. A process of preparing a ferrous metal article for coating-with another metal which consists in immersing the article in a-solution of a caustic alkali passing a current in and then treatalternately opposite directions through the article and solution, from the solution and an acid bath.

SPENCER OTIS. 3 WILSON T. HERREN. i

removing the article then treating it with

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