US1783885A - Apparatus for electrolytically depositing metal on metal tubes - Google Patents

Description

s sheets-sheet 1 Dec. 2 1930.

F. G. MARTIN ET AL APPARATUS FOR ELECTROLYTIGALLY DEPO SITING METAL 0N METAL TUBES Fil ed Sept. 29. 1927 2 193 F. G. MARTIN E A? 3 I APPARATUS FOR ELECTROLYTIGALLY DEPOSITING METAL 0N METAL TUBES Filed Sept; 29, 1927 I Shets-Sheet 2 1930. M RTINEHL 1,783,885

APPARATUS FOR ELEGTROL YTICALLY DEPOSITING METAL ON IIETAL TUBES '1 a f A 1 6 Filed Sept. 29, 1927 3 Sheets-Sheet .5

- Patented Dee 2, 1930 PATENT OFFICE runners enmsna'w marm mm WILLIAM. BAKSAY, or Bmxmuman, ENG AND,

assrenons T0 J. STONE & company LIMITED, or nnrrronn, ENGLAND APPARATUS FOR ELECTROLYTICALLY DEPOSITING METAL ON TUBES Application filed September 29, 1927, Serial No. 222,829, and in Great Britain Aprilj22, 1927.

This invention comprises improvements in apparatus for electrolytically depositing metal on metal tubes or tubular articles and such improvements are particularly applicable for the coating of condenser tubes, superheater tubes and so on, with the object of rendering them incorrodible when in use. The lining of the interior of brass tubes of small diameter with a coating of chromium is most advantageous when such tubes are intended for use in condensers for marine and other work, in which it is of importance to avoid leakage of salt water or other corrosive liquid, into the steam generator system.

The apparatus involves the employment of a flexible anode which is centred andtensioned within the bore of the tube. In this way, it is rendered possible to avoid contact of the anode with the interior of the tube to be coated, whilst preserving a free annular number of tubes of considerable length and small bore and it is important, from the practical and commercial points of View, to provide methods and means adapted for enabling large numbers of tubes to be reliably coated in an eflicient and fool-proof man- 'ner without necessarily involving the employment of skilled labour. Important objects of these improvements include the provision of methods and means calculated to render it possible for relatively unskilled labour to mount large numbers of small bore tubes with their anodes properly centred within them and to.carry'out the electrolytic coating thereof without loss of working time and in a thoroughly reliable manner; The said objects also include the provision of advantageous forms of. anode and means for enabling such anodes to be quickly inserted and ten'sioned within tubes to be coated. Finally, the said objects include the provision of means for enabling end: portions of the tubes to be coated externally whilst the bores be descn ing and holding the tubes and for the mounting and tensioning of anode devices within such tubes whilst leaving the bores and ends of the tubes perfectly free for circulation of electrolyte and escape of gases. The flexible anode may be composed of a number of metal strands or wires which are subjected to compression so that the interstices within the stranded or rope-like anode disappear and maximum cross-sectional area ofconductor metal is obtained for a given diameter of flexible anode. The flexible anode may comprise a non-flexible end portion, for the latter facilitates the threading of the anodes through the tubes and the mounting and fixing of devices adapted for receiving the pressure to be applied by the tensioning means. In order that the labour employed shall not be "required to make sk ilful tensioning adfor producing the tension and to provide means for enabling thesprings to be applied to the anodes so that allwill have a sufiicient and more or less uniform tension, although positively adjustable tensioning means may be employed. Theframing is adapted for supportingthe tubes with their end portions freely exposed, and ring-form or tubular anodes may be suspended or supported around justments, it is convenient to employ springs suchend portions whereby the latter will re ceive an external coating at the same time that the bores are coated. These end portions are those which are jointed in the condenser plates and receive fixing ferrules or the like. The externalcoatings on such end portions protect them against corrosion.

In order to enable the invention to be readily understood, reference is made to the accompanying drawings illustrating suitable examples of electrolytic bath apparatus adapted for carrying out the coating of tubes in accordance with these improvements, in which drawings Figure I is a vertical section of a cylindrical tank containing a frame supporting tensioned anodes and tubes to be coated.

tubes a.

Figure 2 is a plan of Figure 1.

Figure 3 is a vertical longitudinal section of one end portion of a deeptrough-like tank containing a modified construction of frame for supporting tensioned anodes and tubes.

Figure 4 is a vertical transverse section of Figure 3.

Figure 5 is a cross section of an advantageous construction of anode.

Figure 6 is a sectional elevation of anode gripping means which may be used in some circumstances.

Figure 7 is a sectional elevation of a detail applied to the end of a tube.

Referrin to Figures 1 and 2, the tubes a to be plate I. with an'internal'coating such as chromium, the internal anodes b, and external ring anodes c, 0 are all supported in a frame comprising a series of rings d e f g and 72/. As the tubes tobe coated may be of great length, such as eighteen or twenty feet or more, and the tank of corresponding depth, only the top and bottom portlonsof the tank and frame are seen in F igure 1, the middle portion being absent as will be understood from the lines indicating a break in Figure 1.

In a complete or unbroken structure, the frame comprises other rings between the rings 7 and 9 such other rings giving support and guidance to the middle ortions of the tubes to be coated. The num er of such interme dizte rings will depend upon the length of the tu es.

The rings 7 and g supporting the tubes, and the intermediate rings aforesaid, are formed with aligning perforations to receive the The tubes may be secured in the ring 7 by clamping means such as split collets of which one example is shown at the left hand side of Fi ure 1. This split collet a is inserted u wardly into a ta ered hole in the ring an is screw threade to receive a nut afi. y tightening the nut a upon the ring f the collet a is drawn upwardly in the tapered hole and is thereby caused to grip the tube passing through it. The tubesa may be secured'in the ring 9 instead of in the rm f, or they may be secured in the ring 9 as wefias in the ring 7. For example, and as seen to the right hand side of Figure 1, the tubes may be secured in the ring 9 by means of split tapered collets a 'which re uire merel to be pressed down into tapere holes in t e ring ii in order to grip the tubes, the weight of the tter operating to increase the security of the gripping as will be ap arent.

The rings 6 and k are a apted for supporting the anodes b concentrically within the tu es a and for this purpose are formed with perforations axially aligned with those of the rings f and g. The holes in the bottom ring it are tapered to receive conical insulator busheslt' in which the lower ends of the flexible anodes b are engaged or fixed. Thus, the lower ends of the anodes may be knotted or pressed to have a button-like formation which cannot be drawn through the bush h. The perforations of the ring 0 are large enough to receive insulator bushes e which serve for the guidance of the upper ends of the anodes b and also for the seating of tensioning sprin s as hereinafter described. The ring 05 is ormed on itsouter periphery with radially extending clips d which can be tightened on to the upper ends 6 of the anodes and which can also serve for clipping and suspendin the rods 0 of the external anodes hereina er described.

The flexible anodes b are advantageously constructed from lengths of high conductivity copper wire rope drawn-with a covering of lea In order to get rid of interstices and to obtain a maximum cross sectional area of conductive metal with a 1'0 e of given diameter, the said rope may be 'ghly compressed so that the strands acquire more or less the section seen in Figure 5, the lead covering being indicated by b in this figure. Alternatively steel anodes, not requiring a covering of lead, may in some cases'be employed for the coating of large tubes.

The frame comprising the rings d e f g ,h is constructed by mounting these rings on long bolts z in the following manner:--The lower ends of the bolts are rounded to serve as feet and are furnishedjust above such feet with abutments, which may take the form of nuts 2'. The ring it rests upon the abutments or nuts 2" and the superposed rings 9 e f (Z are spacedapart on the bolts by spacer sleeves Z. The top ring d, which serves as a bus bar for the anodes, must be insulated from the bolts 2', sleeves Z, and top securing nuts m, and insulator bushes and washers d are provided for this purpose. The top ring d may be fitted with a terminal post d for connecting itwith the positive terminal of a source of current.

. Uther means may be employed for mounting the rings with appropriate spacing. For example, the sta. be tsz' may be screw threaded throughout t eir length, or over predetermined portions of their length, and nuts screwed on to the rods then serve for supportingr the rings at the desired distances apart.

he cup-shaped tops of the bushes e serve for seating, as aforesaid, springs n which are coiled around the upper end portions of the anodes and press upwardly against collars n adj ustably fixed on the anodes-as by the set screws n. The collars n are set so that the resulting compression of the springs is sufficient for tensioning the flexible anodes b and keeping them taut and concentric within respective tubes a. v v

The collars a may be applied in the manner shown in Figure 6 which has been found to be a convenient and practical method; In this construction the anode is shown as having a portion of reduced diameter forming a groove in which is placed a split collet n having a tapered external surface adapted to be engaged by the tapered internal surface of a collar n. The collar is held down against the pressure of the spring, whilst the halves of the collet are placed in position and is then released to engage the colletand the anode is thus tensioned as will be readily understood. v Or the tensioning of the anodes maybe effected by providing a screw threaded portion at theupper end of each rod and engaging this portion by a fly nut. Suitable expedients, such' as the provision of vertical grooves in the anode engaged by fixed parts ofthe apparatus, may be adopted for preventing turning of the rod during the tensioning adjustment as such turning may be detrimental to the structure of a stranded anode.

A frame constructed as hereinbefore described is loaded with tubes (1 and anodes 6 prior to its insertion into the electrolytic bath in the bank is. The frame may be laid on its side on a bench and the tubes a may be pushed through the perforations of the ring h and then through the perforations of the ring 9 and alsothrough the perforations of any intermediate rings until their ends pass through the perforations of the ring f. The distance of the ring 7 from the ring 9 is' adjusted so thatit is less than the length of the tubes to be plated. The tubes a are inserted so that they project at each end a suitable distance beyond the rings f and g as shown in Figure 1. When in proper endwise position, the tubes are secured by the collets a or a hereinbefore described. The flexible anodes have now'to be passed through th'e perforations in the ring h and through the tubes (1 placed in position in' the frame. In order to assist in threading the anodes through'the small bores of the tubes a, the upper end portion 12 of each anode may be ofa rigid or non-flexible character such as may be obtained by the provision of a steelsleeve passed over the end of the copper rope. The

latter may be opened out and-soldered at' its I end, whilst the lead coating is soldered or burnt on to the steel sleeve in order to prevent the electrolyte (when plating with chromium) from coming into contact Wlth the copper conductor core. When the ends b of the anodes b have been passed through the tubes a they-are passed through the perforationsof the ring 6 and the coned insulator bushes on their oppositevends take a seating in the ring h. The bushes e, springs n, and collars n are now passed on to the rigid ends. of the anodes, the bushes 6'- being seated in the ring 6 and'the collars n' being adjusted to obtain spring pressure as explained above. The bus bar clips d are finally tightened on i the anodes.

One of the stay bolts {is formed at thetop with'an extension 0 which serves for connect-v ing the frame with the negative terminal of the source of current. As the tubes 0 are in good electrical contact with the rings f and g and with intermediate rings of the frame as aforesaid, the frame itself makes a very satisfactory cathode connection. The anode parts are all insulated from the frame as already explained.

, The frame may be suspended from thetank by projections or hooks on the frame engagin" with the top of the tank..

f only the bores of the tubes a had to be plated, the, loaded frame would be ready for being lowered into the bath. However,'it' is bar' d as aforesaid, and these rods being formed or fitted with ring anodes c and 0 which encircle the endv portions of the tubes projecting beyond the rings 7 and 9 respectively. The rods 0 for the main portion of their length are provided with insulating tubes of suitable material such as glass orvulcanite, but the metal of the rings a c is exposed to the electrolyte. The rods 0 may ,be of steel or other suitable material and the rings 0 0 which are made of copper covered with lead are secured thereon in any convenlent manner. The rod 0 should be 1nportions of the rods 0 conveniently enga e in notches in the peripheries of the rings e g.

The flat frame employed in the modification in Figures 3 and 4, comprises end vertical bars such as p supporting horizontal bars f g 'sulated by any suitable means. The straight j and h which correspond with the rings bear- T ing the same reference letters in Fi ure 1. The tubes aware supported and secure in the bars f and g in the same manner as described with reference to the ring construction in Figure 1. The lower ends of the anodes may be flattened, as shown, and covered with-lead buttons 9 which bear against the coned insulator bushings h. A top bar 1' bolted to the vertical end bars p is of hollow formation and.

is fitted with a terminal r for the negative connection. The insulated anode rods 0 pass through perforations in the bar r and the ends of the flexible anodes I) pass through in-- sulator bushes r inserted in other perfora-. tions in the bar 1'. The external anode rods 0 7 are suspendedfrom, and electrically connected with, a copper bus bar .8 by means of binding screw devices as shown, the bus bar 8 resting upon flanges of the bushes 1" and beingthereby insulated from the bar 1'. Screw threaded sleeves t are secured to the upper ends of the anodes b and screw into nuts t resting upon the bus bar 8. The flexible anodes b are tensioned by adjustment of the nuts t as will be a parent from Figure 3. The lower ring ano e a may be formed by bending the rod 0, the vertical ortion of which in the case of chromium plating should have a steel covering, after the latter has been inserted through the bars 7 and g, or it may be detachably mounted on the rod a like the upper anodering c in Figure 3.

It is to be understood that the means shown for the external plating of the ends of the tubes is merely one example of con: struction, it being advantageous to employ instead of the rings 0, c tubular anodes extending over the ends of the tubes and of a length approximately equal to the length of external plating-it is desired to apply to the tube. Also it is contemplated that ring or tube anodes may be'supported to the centrail anodes 6 thereby dispensing with the ro s a. v

The hollow top bar 1' with its end walls Wand side walls 1* forms a hood at the top of the frame. Baflies may be provided in the hood and gases collecting during the electrolytic process may be drawn off through a connection 7- by a fan so that they are discharged where they can have no harmful effect on the workmen. A door may also be arranged in the hood through which the frame is adapted to be lowered and lifted. If desired, a similar hood could be provided for the construction illustrated in Figures 1 and 2.

To-prevent 'undue rise of temperature in the bath during the process a cooling pipe or coil such as 24. Figures 1 and 2, may be provided for the circulation of cooling fluid.

As shown in Figure 7 a small hollow vulcanite cap a may be fitted on the outside of each tube at its ends, these plugs being formed with holes w for the passage of the anodes b and with small holes w in their cylindrical portions to permit of the circulation of the electrolyte, it having been found that the provision of these caps enhances and improves the coating of the tubes at their ends. Although the cap is shown vas merely gripping the tube any suitable means may be employed for connecting the caps to thetubes.

The cross sectional area of the flexible anodes is'usually such that they will carry the deposition current without serious drop of potential at the lower end when current is .led into the upper end only. Acertain drop of: potential is inevitable but is compensated by the fact that the electrolyte is more concentrated at the lower ends of the tubes to be coated. If desired, current maybe supplied to both ends of the flexible anodes b, in which case the lower'ring or tube anodes o maybe supported upori' the lower -bus bar which would then be used, or they may be supported upon the lower end portions of the flexible anodes b.

By the hereinbefore described method and apparatus it is possible uniformly to coat with chromium large numbers of brass condenser tubes of the usual diameter and bore and of lengths up to eighteen and twenty feet or more. No particular degree of skill is necessary for the mounting of the tubes and anodes in the frames, for uniformity of positioning of the tubes and of tensioning of the anodes can be readily attained with ordinary care. Also, no particular degree of skill is required for supervising the electrolytic process, the degrees of current strength and electrolyte concentration and the plating period and bath temperature, being all prescribed for a given job. The details of construction will, of course, be modified to suit the plating of tubes of lengths, diameters and bores.

Before commencing the electrolysis it may be necessary to effect a washing or pickling of the tubes as byv dipping them in waste chromic acid with or without an addition of sulphuric acid. Also after removal from the electrolytic bath it is necessary to wash the tubes and frame to free them of chromic acid. The tubes, being securely mounted in the frame, are readily lowered into and removed from washing or pickling baths and are conveniently disposed for the running of cleaning brushes such as wire brushes, through their bores or for treatment by water jets and so on. The conveyance of the frame and tubes from and to the various treatment tanks may suitably be effected by lifting means of an convenient form. After removal from t e frame, the washed tubes may be stacked to drain and dry. Whilst the coating of one batch of tubes is proceeding, the workman is employed in loading a second frame with tubes 1n the manner described, this second batch being introduced into the bath when the first batch is finished, as will be readily understood.

It will be noted that in securin the tubes in the frame and tensioning t e anodes therein as above described, the tubes are not subjected to axial compression so that there is no influence tending to bend and destroy the straightness of these long thin tubes of small diameter. On the other hand, the said tubes being su ported each in a number of axially aligne perforations'there is a positive tendency to preserve their straightness. Also, the tubes and flexible anodes being supported in a-truly vertical position and the anodes being tensioned, there is no tendency for the anodes to sag or bend and to lose that concentricity or axial alignment which is important for the attainment of uniform and reliable coatings.

When brass. tubes are to be coated with different chromium a loaded frame may be lowered into the bath before the current is switched 1 on, the electrolyte acting preliminarily as a frame is lowered into the bath.

We claim s Electrolytic apparatus comprising a frame having (and members and a series of intermediate members, said intermediate members being perforated to receive the tubes to be coated, gripping devices arranged in said perforations and ada ted for fric-. tionally engaging said tubes, exible anodes supported concentricall within the tubes between said end mem ers and tensioning means operative between one of said end members and said anodes for tensioning said anodes.

2. Electrolytic apparatus comprising a frame composed of longitudinals, end members, and a series of intermediate perforated members, spacers for distancing said intermediate members along saidlongitu'dinals,

collets associated with said intermediate members for frictionally engaging tubes guidingly inserted throughthe perforations of said members flexible anodes supported by saidtopan bottom members concentrically within said tubes and tensioning means operative between one of said end members and said anodes.

3; Electrolytic apparatus comprising a frame composed of longitudinals, end members, and a series of intermediate perforated members, gripping means associated with said intermediate members adapted for frictionally engagin tubes guidingly inserted through the per orations of sald members, the uppermost and lowermost members of the intermediate series being so disposed that the ends of the tubes project beyond them, external'anodes adapted to surround said projecting ends of the tubes, internal flexible anodes disposed within said tubes and extended between said end members, and

tensioning means operative for tensioningv said internal anodes. Y -4. In electrolytic apparatus for carrying out processes of the kind referred to, the

combination of a tank, a frame adapted to y be supported within said tank and comprising top and bottom members and intermediate perforated members, gripping devices associated with one of said mtermediate members and adapted for frictionally engaging the tubes, flexible anodes mounted concentrically within said tubes, tensioning means for said anodes, external anodes adapted for coatin the ends of said tubes, and insulated con uctors supporting said *externalanodes.

5. In' electrolytic apparatus for carrying out p o the kind referred to, v the combination of a frame comprisin end rings and a series of perforated interme iate rings,

grippin devices associated with one of said interme iate rings for frictionally engaging tensioning means operative between an end ring and the upperparts of said anodes.

6. In electrolytic apparatusfor carrying out processes of the kind referred to, the combination of a tank, a cathode frame comprising end rings and a series of intermediate perforated rings, gripping devices associated with one of said intermediate rings adapted for supporting tubes inserted into the perforations of said intermediate rings, flexible. anodes arranged between the top and bottom rings and within the tubes, abutments on said anodes, compressionsprings between an end ring and said abutments, and electrical terminal means for said anode and said frame.

7. In electrolytic apparatus for carrying out processes of the kind referred to, the combination of a tank, a cathode frame comprison said anodes, compression springs between an end ring and said abutments, a terminal devlce connected wlth'sald anodes, insulated conductors suspendedfrom said terminal de- -v1ce, anodes supported by said conductors and adapted to surround the ends of the tubes, and an electric terminal for said cathode frame.

8. Apparatus forcarrying out processes of the kind referred to, comprising a-tank, a

frame adapted for vertically supporting a' number of tubes by slidingly engaging the latter at several points along their length, flexible anodes mounted in said frame and concentrically within said tubes, tensioning means forsaidanodes, and a hood device surmountin said anodes and adapted for the discharge 0 gases evolved during the process. 9. Apparatus for carrying out processes of .the kind referred to, comprising a tank, a frame adapted for vertically supporting a number of tubes by sildinglyengaging the latter'at several points along theirlength, flexible anodes mcungedcon ntrica wi said tubes, tensioningi'iibans for sai anodes and external anodes surrounding the ends of said tubes. 1

10. Electrolytic apparatus com rising a frame for supporting a number 0 tubes by slidingly engaging the latter at several points between their ends, and tensionin means for anode rods extended through sai tubes. 1

11. Electrolytic. apparatus comprising acathode frame composed of a'serie's of horizontal members, accuratel aligned holding devices associated with sai members mfor vertically supporting a number of tubes at several points between their ends, flexible anodes mounted concentrically within said tubes, and tensioning means for said anodes.

12. In electrolytic apparatus, the combination of a tank, a frame adapted to be supported within said tank and com rising intermediate members, accurately ahgned holding devices associated with said intermediate members for sup orting a number of tubes between their ends, end members adapted to support flexible anodes concentrically within sai tubes, and tensioning means for said anodes.

13. In electrolytic apparatus, the combination of a tank, a frame ada ted to be supported within said tank an comprising a series of horizontal members, accurately aligned holding devices associated with said members for vertically supporting a number of tubes at several points between their ends, spacers for separating said frame members, end members on said frame for su porting flexible anodes within said tubes, and tensioning means operative between said end mem bers and the anodes. p

14. In electrolytic apparatus, the combination of a tank, a frame adapted to be supported within said tank and comprising top and bottom rings and a series of intermediate 7 perforated rings, spacers for said rings, ac-

curately aligned holding devices associated with said intermediate rings, flexible anodes supported between said top and bottom rings, and tensioning means operative between said frame and the anodes.

FRANCIS GRIMSHAW MARTIN. WILLIAM RAMSAY.

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