BE474253A - - Google Patents

Description

       

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  Coating.



   This invention relates to electroplating and more especially to a new process thus due to the product resulting therefrom.



   When applying metal electrolytic deposits to blanks, it is desirable to create a predetermined thickness of electrolytic deposit more quickly, with as large an amount as possible. In galvanoplasty, quality is such an important factor that speed is almost invariably sacrificed if it is necessary to obtain a good quality of electroplating. In current practice, it is well known that the highest degree of experience as well as unrelenting care and attention is required to produce uniform electroplated deposits of high quality.

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  Acceptable electroplating from a cOY'Jr: 1ercie.l point of view requires a. homogeneous coating, uniform and smooth. In many cases, the coating should be as shiny as possible to avoid further processing of grinding and excessive polishing. often content with a non-homogeneous, relatively irregular and
 EMI2.2
 dfpl? isB'111 'slow rough, because either it is too expensive to do a better job or, as is often the case
 EMI2.3
 In this case, one cannot produce an --old recovery. We then rely on polishing rt ', C2nlCue to 8mltorer the 4% state of the plated zal.
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  Usually, electroplating must be carried out with relatively minimal current densities, in order to be certain of ensuring a satisfactory metallic deposition. Likewise, the gavnoplasty of irregularly shaped objects requires considerable experience, from the point of view of the arrangement of the anodes.
 EMI2.5
 and the judicious choice of current densities and electrolyte composition.

   Thus, a cylindrical part t * 1% e ai.i'vn tube or a wire can be reopened by. electroplating with relatively high current densities and a plated metal is obtained generally of fairly good quality. Retort we treat
 EMI2.6
 more and more irregular shapes many .m8S nrobls arise and it becomes more and more difficult to ensure a uniform and horiogenic electrolytic deposit. A? square sheet is much more difficult to plate successfully than a cylinder, while a part with protrusions, recesses and cavities requires special conditions to ensure a good overlap work,
 EMI2.7
 We have experienced great difficulties p / -L ti-3iJli.érpr # mnt.



  P cover, by electroplating, rough pieces of thick 6tallirtues deposits with a Fryer equal to or greater than µ 0.01 '(0.25: in). The electrolyte deposits toe (the Y1t to become more lumpy, rough, of irregular thickness and

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 often present as coarse, crystalline or branched coatings. It has been found that electroplating tends to deposit good metal early, but that the structure and appearance of the deposit quickly becomes poor as the operation is continued.



   By treating a blank with any electrolyte solution, the allowable current density is limited to. value which impoverishes the electrolyte located in the immediate vicinity of the treated part so that the number of ions of the metal is no longer sufficient to correspond to the electric current applied. Beyond this value, a certain quantity of the water in the electrolyte begins to decompose and hydrogen forms on the surface of the part being treated. This reduces the efficiency of the covering, as the hydrogen tends to cover the surface of the part. This phenomenon is known as polarization. The recovery is usually carried out at such a rate as to prevent the occurrence of a large polarization.

   A certain bias appears even in the most carefully conducted collection operations, but can generally be kept within reasonable limits. The polarization causes inefficiency and irregularity of the coating and thus causes losses in the entire coating process.



   The present invention provides for the application, to the part being treated, of current following a determined cycle: the current is applied so that a given thickness of metal is deposited electrolytically on the part, at predetermined intervals, then the current is reversed so that part of the electrolyte layer is removed, precisely the weak and low quality part. In this way, the blank is covered in such a way that it acquires a uniform deposit composed of a large number of particles of pure, very fine and homogeneously bonded metal. We have found many advantages in performing recovery

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 EMI4.1
 electrolytictue of parts according to the current cycle in accordance with
 EMI4.2
 this invention.
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  We have. Formerly suggests performing electroplating by interrupting the operation at intervals and briefly juversing the current for a small fraction of a second in order to depolarize only the top layer and then resuming the operation. d! t / test '' '' 'fait does not produce any improvement..On the contrary, we = .Xr.tise completely unexpected excellent recoveries in <' DPliom'l1t, conform: l1 () jent to the invention, a sufficient reverse current during a tS "1PS long enough to remove the l2 part of the solid neutral covering and of low qunlit40 The main aim of the invention is to convert the gplvanoplpstir11J8 pot into an electrolytic layer. pure and} 1C- 1'ro <9ne.



  The invention consists of: r111C2? ' e "'Pnt pn a DrocÂè! / deposit ?? lot'1J¯iCtJ plectl'olytin1Je on a piece 1W1Jt0," 11 '11 .0'18''1 d'BQ lsctro1yte; iI includes the: pyclica tion of 1. 'electro17te 1. 1 niece has, rute9 le p, r'ss "f': e of 111'1 current Atec.rirue 1 feed the part and the electrolyte in order to make this piôcr- cpth0è! iue, during the same period of time pr4âàtetmin'p, éJr-ns the nl1t to deposit '!; electrolytiq1J81' slow of "'71! tpi on 18 rd8ce, the inversion of the current in order to make the same part pnodirue, the current 2vpnt a density such and Rtant apply for vn te '"r) s sufficient for the weak metal and bass (" l1lit ôposÀ electrolytio1Je'11ent be removed ;, the Y (' 8tel d ± pcsÀ! 18ctrol ,, 'tiC'lJ': Plent ( not the part itself) being soluble d 0ns 1 - ': fiīecttolyrte during the application of the reverse current:

  , and the "repetition of the current cycle until no previous thickness of pure metal has been deposited flectrolyt 5.01J8", "Ocmt
 EMI4.4
 on the part.
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 The invention will become clear after 1 "description
 EMI4.6
 following detailed description given by way of example and illustrated in the accompanying drawing.
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  .

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   The fig.l is a vertical section of an electroplating device.



   Fig.2 is a graph giving the time as a function of the current used in the galanoplastic cycle.



   Fig. 3 is a cross section, fragmentary and greatly enlarged, of a blank and its electrolytic coating deposited by conventional methods-,
Fig. 4 is a fragmentary and greatly enlarged cross-section of a blank and its electrolytic deposit deposited according to the process according to the invention.



   Fig.5 is a perspective view of an electromagnet, and Fig.6 is a perspective view of a rectangular frame.



   According to the invention, not only can the electroplating be carried out at higher speeds than those which are usually possible, but, more importantly, the quality of the electrolytic deposits produced can be controlled so that they are greater than all that has been obtained previously in the technique of recovery.



   In summary, it has been found that the electroplating process as well as the electrolytically produced deposits can be greatly improved by applying an alternating current to the workpiece subjected to electroplating, whereby the workpiece is alternately cathodic for a period of time ranging from about 2 seconds to 40 seconds, then anodic for a period of time ranging from about 0.5 sec. at 10 seconds. The anode phase of the current cycle should be of sufficient current density and be applied for a time long enough to loosen the weak, low quality metal deposited during the previous cathode phase of the cycle.

   In particular, the anode or "off-plate" part of the cycle should apply at least 10% of the 'Coulombs of the current supplied to the raw partēduring the part.

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 EMI6.1
 cathodic cycle. The best results are obtained 1: 1 1) for the overlap of almost every 1.it.vi> x, when In pnpse pnodiaue of the current applies to the part between 20 and 40 "1 of the Covlornbs of the current applied during the cithodinous cycle of cy-
 EMI6.2
 key.



  The cathodic phase of the cycle will recover may
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 have a current density many times greater than the allowable current density in the DC ssicue recovery process. Since the recovery phase of the cycle lasts only about 2 to 40 seconds, the polarization is negligible and does not pinch to such a severe degree what would appear if there is. same current density made
 EMI6.4
 used with the use of direct current. When the current
 EMI6.5
 is reversed and the part made pnodinue, it is often sovbmit, -bl.e to transmit a current density nuelou: Jeu Sl1neure than that of the cathodic phase of the current or overlap nh ^ se of the cycle.

   In many cases, excellent results are obtained when the current density is reduced. t from 50 to 100 more 7¯eve than the current density c> thodic.



  Many unexpected results have been obtained by electrolytically depositing a -tpl onto a blank with an electrolyte making use of the AC cycle which constitutes the article of this invention. The speed required for depositing metered data on a blank is highly 2 CC1Je, and in many cases, the recommended thickness of the jar will not be applied by means of the jar. :! ê'J1e electrolyte, in a terrrps comprised between 50 and 20V of that necessary when only the continuous current is used. However, the main advantage is Ip or? ltt rprnU2ble of the 7lpt81 d4pos 'p, electrolytiouement pp' The process according to this invention The surfaces of the electrolytic deposits are much more shiny.

   In many cases, deposits -1 pc- 5l,

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 Trolytics created in practice by the present invention are so smooth and polished that nothing comparable has ever been obtained before by any electroplating process.



  ..In almost all cases (except in the case of chrome, as will be explained later), the equality, la. hardness, uniformity, color and corrosion resistance of the metal electrolytically deposited by the process according to this invention are absolutely superior to those of the same metals covered with the same electrolyte using current continued. Other advantages of the invention will become apparent later, when the process will be described in detail.



   Fig.l of the plan shows an electroplating tank 10 provided with an inner jacket 12, chemically unassailable, in which is the electrolyte 14 having a composition suitable for plating the desired metal. Conductor bars
16 and 18 are each powered by the alternating current source 20 meeting the requirements set forth herein. The alternating current source 20 may be an alternator designed to generate current according to the desired cycle. In other cases, the alternating current source 20 may be a direct current source, such as a battery, dynamo or rectifier, which is combined with suitable relays reversing switches and with switches. resistors actuated by a timer, in order to reverse the current at predetermined times in accordance with the invention.

   In other cases, one can imagine. other appropriate mechanisms to achieve the desired current cycle. The conductor bar 16 carries a hook 22 which holds the blank 24 to be pressed. The hook 26, supported by the conductor bar 18, carries a suitable anode 28.



   Fig. 2 of the plan illustrates the cycle of the alternating current which is applied to part 24 by generator 20. At point 0-A, blank 24 becomes cathodic and begins to cover itself with metal. For most purposes, the current density in A will be greater than that normally used.

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 However, by using direct current only, everything else is equal. However, it should be heard naked. It is not essential to use higher currents or those normally employed when using direct current only. This will ensure an excellent re-rating of the blank, even if the current density in A @ is lower than normal.

   The present invention results in a wider range of current densities than before. The only limitation is that the current density at A must not reach such a high value that the plated metal overheats or excessive gas evolution or other effects occur during the brief moment when the part is cathodic. The time from A to B can be roughly between
2 to 40 seconds. The time chosen will depend on the electrolyte to which the process is applied / the shape of the part being treated, as well as other conditions. The cathode current between A and B is figured as a constant current.

   However, the current does not have to be uniform; it can be wavy or pulsating, for example by superimposing an alternating current on the direct cathode current, or the current may have a higher value at point B at point A. Usually, however, the current between A and B will be relatively constant, since a uniform current is most easily and economically obtained. At point B, the current is suddenly reversed to the value C, and part 24 is rendered anodized. As shown, the density of the anode current at C is greater than the density of the cathode current.

   In most cases, it will be found that no higher anode current density is required to ensure the results advertised by the invention. However, in many cases it has been found that the density of the anode current may be the same as the density of the cathode current. The important criterion of the anodial or inverted current in C, is that it is related to the electrolyte so that a

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 good amount of the electroplating layer is removed. The anode current is applied for a period of time ranging from about 0.5 to 10 seconds, depending on the corresponding cathode or recovery current.

   The product of time by the anode current should have a Coulomb value equal to at least 10%, and preferably between 20 and 40%, of the Coulombs of the current applied during the cathode part of the cycle. The current between C and D does not have to be constant as shown: it can be wavy or pulsating or variable in any way. In D, the current is again reversed, the blank is made cathodic and the cycle begins again. In all cases, the cycle will be asymmetrical. The 0-A-B-C-D-E cycle is repeated until a suitable thickness of metal covers the blank. The blank is removed from the electrolyte 14 preferably during the CD portion of the cycle, when the part is anodic, since the polish of the plated metal is best at this time.



   When the. part 24 is subjected to the current cycle shown in FIG. 2, it will be noted that the electrolyte 14dépov Vitesse between points A and B, for approximately 2 to 40 seconds. Experience has shown that the metal deposited during this time does not have a uniform quality, but an irregular quality. It has been found that the metal deposited first is of better quality and is more solid than the metal deposited afterwards; in particular, the subsequently deposited metal becomes less dense, coarser in structure and less polish and uniform. Sharp protrusions, raised spots, and corners tend to firm the deposited metal more quickly than flat areas or indentations.

   When subjected to the anode portion of the cycle between points C and D, the low quality, weak metal is removed, leaving an electroplated deposit of very good metal. The "unplating" part of the cycle does not do more than remove loose metal. Experience shows that the previously deposited metal

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 The excess material is preferably dissolved so as to remove more metal from rough corners, edges and protrusions (such as high points, knots and the like which are microscopically raised) than from flat areas and general surfaces.



   Scratches, pores and other discontinuities and imperfections in the surface of a raw part are likewise unexpectedly dealt with by the overlap done in an alternating current cycle. Referring to figs. Z and 4 of the plan, these illustrate greatly enlarged cross sections of a blank 30 having a burr 32, a scuff 34 and a pore 36 composed of a relatively non-conductive inclusion, such as, for example, a grain of metal oxide, slag, coal or sand. On the part of FIG. 3, when it is subjected to the normal direct current coating, the electrolytic deposition of metal tends to strongly accelerate its growth on the burr 32, according to a well-known phenomenon.

   As a result, a knot 38 is created on the burr 32, particularly if the overlap is of appreciable thickness. At the scratch 34, the electroplated metal forms an exaggerated hollow 40 which has relatively vertical flanks which are thicker than the main portion of the electroplated metal, while the hollow of the scratch is deposited at a thickness. less than in the main part of the electrolytically deposited metal. At pore 36, the electrolytically deposited metal forms a slightly thicker lip surrounding the pore without any metal being deposited in practice on the relatively non-conductive inclusion. It is evident that the surface of the plated part 30 of Fig. 3 becomes rougher as the coating is continued.

   For resistance to. corrosion, the deposited metal is not satisfactory, since there are parts much thinner than the average thickness of the deposited metal and since these

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 weaker parts will obviously give way before the average thickness of the deposited metal is attacked.



   Fig. 4 of the drawing shows a plated blank 30, which shows the improvement in electrolytic deposition achieved by the use of the alternating current coating process according to the invention. When the blank 30, which has a burr 32, a scuff 34 and a pore 36, is subjected to electroplating following the alternating current cycle, a corresponding projection is electrolytically deposited on the burr 32; however, it has a larger radius and much less difference in height with the neighboring middle layer of metal than would occur with direct current overlap. No nodules form. It will be found that the metal is plated over the scratch 34-such that it almost fills the scratch. Consequently, the scratch is made less prominent.

   This now results in better protection as well as a more even surface. The inclusion 36 is soon-completely covered by the method of the current invention. It will be apparent that the surfaces created by the coating according to the invention are smoother than the original surface of the raw metal. The uniformity of the plated metal is far superior to any electroplating previously produced by conventional methods. It should be understood, of course, that only small or microscopic irregularities are equalized. ' The main contours of the blank are totally followed and matched by the deposited metal.



   Unexpected results, like those shown in the. fig.4, can for example be explained as follows but can also come from other causes arising from the process of this invention. After the metal has been deposited on the raw part 24 for about 2 to 40 seconds, low quality, weak metal is removed during the next anode part of the cycle and is redissolved in the immediate vicinity.

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 of the blank. Any elevations, corners or protrusions, are "displaced" at a faster rate than the major planar regions of the electroplate. There is more metal 44 removed at the burr than on the rest of the cover.

   The metal in the scratch 46 'is removed at a slower rate than the lips of the scratch or other parts of the curl.



  When the cathode portion of the recovery cycle is reapplied to the blank, the concentration of the metal in the vicinity of the blank is abnormally high and therefore the recovery begins and is maintained for part of the period with a approximate 100% yield, in lots of electrolytes. The concentration of the metal in and near the scratch 34 is high enough to quickly flatten the 2 sides of the scratch, and the scratch is filled in faster than the main layer of deposit metal. However, protrusions such as 44 do not thicken much more than the main layer. Therefore, no knotting or developing effect occurs.

   By being repeated, the anodid part of the cycle again reduces the protrusions in preference to scratches or scratches. other microscopic hollows and a progressively more uniform surface is thus obtained. The anode part, combined with the cathode part of the current cycle, will impart new and unforeseen characteristics to the plated metal.



   Other beneficial effects ensured by. the anode part of the cycle resides in the metal ion reloading near the blank, removing low quality and weak metal. The anode part of the cycle therefore does not represent wasted energy since the recovery during the. subsequent cathode part of the cycle is activated and is more efficient as a result of the replenishment of metal in the nearby electrolyte.

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   In practice of the invention, exceptionally favorable results have been obtained by electrolytically depositing copper, brass and silver. Electroplates of zinc, nickel, tin, cadmium and gold have been produced which are superior in many respects to those obtained by any conventional electroplating process.



   In all these cases, the electrolytes used spread out those used normally. No substantial modification of the composition is necessary to obtain the advantages of the present invention. It was found that the current cycle. The alternative of this invention gives good results not only with conventional recovery electrolytes but also with electrolytes modified to better match the current to the metal to be treated. A single exception was encountered in the chromium deposit when the reverse or "displacement" current was applied, it was the raw metal which came off instead of the chromium foil.

   Some examples follow, of various electrolytes, employed and metals deposited with the AC cycle according to this invention:
EXAMPLE l.-
An electrolyte containing copper 7.35 ounces per gallon (208.37 gr. Per 3.78 lit.) was prepared uncombined potassium cyanide 1.80 ounces per gallon (42.52 gr. Per 3.78 lit.). ) potassium hydroxide 2.48 ounces per gallon '' (70.3 gr. per 3.78 lit.) additional agent :. 8 ccm per gallon '(3.78 bed).



   The complex shaped blank 50 shown in FIG. 5 of the drawing was covered in an electrolytic bath as shown in fig.l. Part 50 is an iron-cobalt alloy electromagnet having an approximate area of 1/12 of a square foot (0.0077 m2). The conditions set required for the electrolytic coating a thickness of copper, ranging from approximately 0.018 "to 0.020" (0.45 to 0.50 mm), having a total weight of between 28 and 33 grams. We will immediately recognize-

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 ment that the covering of the part 50 would be very difficult if a reasonably smooth and uniform plating was required. The temperature of the electrolyte varied between 140 F and 210 F (60 to 99 C). The pH was maintained at 12 or above.

   Electrode 28 was a copper anode. Part 50 was treated in the copper electrolyte, following the following cycle of alternating current:
 EMI14.1
 
<tb>
<tb> Time <SEP> Running
<tb> Cathode <SEP> 15 <SEP> seconds <SEP> 65 <SEP> Amps <SEP> per <SEP> foot <SEP> square <SEP> (0.0929 <SEP> m2)
<tb> Anode <SEP> 3 <SEP> "<SEP> 100 <SEP>" <SEP> <SEP> "<SEP> (0.0929 <SEP> m2)
<tb>
 The effective current density was 37 amps per square foot (0.0929 m2). In a plating time of 5 hours, several magnets corresponding to part 50 were coated with 3.7 and 32, ¯ gr. copper, respectively.

   To ensure the same weight of copper on the electromagnets, the recovery required between 9 and 11 hours with the copper plating system known to be the fastest and usable with direct current. In addition to the faster recovery by the process of this invention, the copper foil deposited on part 50 was brighter and more even than any previously known copper plating. She was extremely adherent.



   Samples of the copper coating produced by the process of this invention were removed at magnet 50 and their density was found to exceed by about 25 to 50% the density of a copper coating of equivalent thickness. - slow, as good as it would be possible to get from a direct current bath of roughly the same composition. The coppery metal prepared by the practice of this invention was flexible and much harder than conventional thong deposited copper. The latter broke easily when bent in a finger and exhibited a rough crystalline structure, while the copper foil of the present invention did not break and instead exhibited considerable elasticity when bent. in the hand.

   When n

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      From the breaking of the copper foil of this invention, it was observed that the struture was much thinner than that of the best direct current plated copper.



   Various copper blanks using the AC cycle of this invention have withstood corrosion much better than conventional copper plating. Through. For example, a thickness of 0.000511 (0.0127 mm) of copper plated by direct current on steel plates offered less resistance to corrosion by a salt spray jet than a thickness of 0.00035 "(0 , 0089 mm) of copper plating produced by the process of this invention.



    EXAMPLE II.-
A copper cyanide electrolyte similar to that of Example I was applied to a part identical to that shown in Fig. 5 of the plane subjected to electroplating following the cycle below.
 EMI15.1
 
<tb>
<tb> current <SEP> time
<tb> cathode <SEP> 15 <SEP> seconds <SEP> 90 <SEP> amp. <SEP> by <SEP> foot <SEP> square <SEP> (0.0929 <SEP> m2)
<tb>
 
 EMI15.2
 anode 5 he 90 he he he he rr
The effective current density was 45 amps. per square foot (0.0929 m2). In 3, 1/2 hours, were deposited on the part 30.37 gr. of copper having a thickness of 0.012 "(0.3 mm).



  The copper film had a very smooth and shiny appearance. Electrical strength testing of the copper film indicated that it was as conductive as 31 grams (thickness 0.01811, or 0.451 mm) of copper applied through the same bath for a period of 11 to 12 hours using direct current.
 EMI15.3
 



  EXAMPLE III Either the following copper-Rochelle salts electrolyte:
 EMI15.4
 
<tb>
<tb> Cyanide <SEP> of <SEP> follow <SEP> 4 <SEP> ounces <SEP> per <SEP> gallon '<SEP> 113 <SEP> gr. <SEP> by <SEP> 3.78 <SEP> lit. <SEP>)
<tb> Sodium <SEP> <SEP> <SEP> <SEP> 5.1 <SEP> "<SEP> 145 <SEP>"
<tb> Sodium <SEP> carbonate <SEP> <SEP> 2 <SEP> "<SEP> 57 <SEP>"
<tb> Sodium <SEP> <SEP> <SEP> <SEP> 5.1 <SEP> "<SEP> (145 <SEP>")
<tb>
 The electrolyte temperature was 160 F (71 C).

 <Desc / Clms Page number 16>

 
 EMI16.1
 The following alternating current cycle is applied to the complex shaped piece of lp:

   
 EMI16.2
 
<tb>
<tb> Current <SEP> time
<tb>
 
 EMI16.3
 cathode 14 seconds 90 8p. per foot cprrp (0.0929 m2)
 EMI16.4
 
<tb>
<tb> anode <SEP> 3,5 <SEP> "<SEP> 120 <SEP>"
<tb>
 
 EMI16.5
 The effective density of the current is near 48 ^ per square foot (0.0929 m). The warehouse produces electrically stc: i t polished and 1J11i. Copper has a r <11,:, aissi 'high lity than c, it produces with 16 cyanide electrolyte si.n; 1-e of Examples I and II.



    EXAMPLE, 17.-
 EMI16.6
 An electrolyte for the pitonation is prepared as follows
 EMI16.7
 
<tb>
<tb> cyanide <SEP> of <SEP> copper <SEP> 30 <SEP> gr. <SEP> per <SEP> liter
<tb> <SEP> zinc <SEP> cyanide <SEP> 9.49
<tb> <SEP> sodium <SEP> <SEP> 56 <SEP> cyanide "
<tb>
 
 EMI16.8
 The temperature of the electrolyte is 100 F (78 C) <Rectangular steel plates with an area of 0.1 feet
 EMI16.9
 copper-plated c9rrÁ (0.009s m2) were coated in the brass electrolyte by using the following decreasing values:

   
 EMI16.10
 
<tb>
<tb> times <SEP> are running
<tb>
 
 EMI16.11
 cathode 3 seconds 150 to 25 amD.p2r square foot (0.0929 mu}
 EMI16.12
 
<tb>
<tb> anode <SEP> 0.8 <SEP> "<SEP> 95 <SEP> to <SEP> 67 <SEP>"
<tb>
 The effective current density was 50 amps. -because
 EMI16.13
 square foot (0.0929 nW). An unexpected result was that the electroplated deposit was a very shiny brass. It is often possible to obtain shiny brass directly by plastic surgery; previously this has never been commercially split possible for any known coating process. Brass film tests have shown (lU it was more equal and more homogeneous than the usual 1-layer film, just as it adhered more strongly and was much more resistant to corrosion.

   The brass was more compact than that obtained by direct current electroplating.

 <Desc / Clms Page number 17>

 



  EXAMPLE V.-
A zinc electrolyte was prepared with the following constituents:
 EMI17.1
 
<tb>
<tb> <SEP> zinc <SEP> cyanide <SEP>. <SEP> 8 <SEP> ounces <SEP> per <SEP> gallon <SEP> (227 <SEP> gr. <SEP> per <SEP> 3.78 <SEP> lit.)
<tb> <SEP> sodium cyanide <SEP> 5 <SEP> "<SEP> (142 <SEP>" <SEP>)
<tb> <SEP> sodium hydroxide <SEP> 11 <SEP> "<SEP> (132 <SEP>" <SEP>)
<tb>
 
Rectangular sheets having an area of -0.1 square feet (0.0093 m2) were coated with zinc electrolyte under the following conditions:
 EMI17.2
 
<tb>
<tb> current <SEP> time
<tb> cathode <SEP> 15 <SEP> seconds <SEP> 60 <SEP> amp. <SEP> by <SEP> foot <SEP> square <SEP> (0.0929 <SEP> m2)
<tb> anode <SEP> 2 <SEP> "<SEP> 65 <SEP>" <SEP> It
<tb>
 
The effective current density was 45 amps per square foot (0.0929 m2).

   A uniform and smooth zinc deposit was produced thanks to the electroplating cycle of this. Example. The zinc surface exhibited a gloss equal to that produced by the best direct current process known today. Additionally, the zinc of this example was deposited as a thinner and more uniform coating than any other coating produced heretofore.



  EXAMPLE VI. -
An electrolyte for cadmium plating had the. following composition:
 EMI17.3
 
<tb>
<tb> <SEP> cadmium <SEP> oxide <SEP> 3,5 <SEP> ounces <SEP> per <SEP> gallon, <SEP> 99 <SEP> gr. <SEP> by <SEP> 3.78 <SEP> lit.)
<tb> <SEP> sodium <SEP> <SEP> 14.5 <SEP> "<SEP> (411 <SEP>") cyanide
<tb>
 
A steel part, consisting of a rectangular sheet 0.1 square foot (0.0093 m2) in area ;, was immersed in the electrolyte and plated with the following current:
 EMI17.4
 
<tb>
<tb> times <SEP> are running
<tb> cathode <SEP> 15 <SEP> seconds <SEP> 40 <SEP> amp. <SEP> by <SEP> foot <SEP> square <SEP> (0.0929 <SEP> m2)
<tb> anode <SEP> 2 <SEP> "<SEP> 60 <SEP> Il <SEP>" <SEP> "
<tb>
 
The effective current density was 28 amps per square foot (0.0929 m2).

   The cadmium plating produced was a notable improvement over any known cadmium plating with direct current.



  The overlays were exceptionally smooth and provided a shiny, polished appearance.

 <Desc / Clms Page number 18>

 
 EMI18.1
 



  In such a penetrator, steel samples were coated in the c! "'D1: 1ium electrolyte, under the following conditions:
 EMI18.2
 
<tb>
<tb> current <SEP> time
<tb>
 
 EMI18.3
 cathode 15 seconds 60 1 # ap <ppr foot cprr '((0, 08;:? f) mù) 8nOde 2 if 60' 1 '1
 EMI18.4
 The effective current density is au5 pn. for square foot (0.0929 m2). The C ^ d "'¯1?; E obtained by following this cycle ev-'it a G 1.18 11 t, (also weighs that' 0.r001Ji te (':] 1 s? C0nfor- = 1rnt eu cycle of run previous.



  E: #E. '. PLL VII.A silver electrolyte has 4t' pr0p "" l "! With I." following composition: silver cypnure ................. 40 gr. per liter
 EMI18.5
 potassium cyanide ............. 62.5 fi potassium cyanide in the free state 40 "potassium carbonate ........... 50"
 EMI18.6
 potassium hydroxide .... ...... 10 tel
The bath temperature was 80 C. The following AC cycle was used:
 EMI18.7
 running time
 EMI18.8
 
<tb>
<tb> cathode <SEP>, <SEP> 20 <SEP> seconds <SEP> 15 <SEP> amp. <SEP> by <SEP> foot <SEP> square <SEP> (0.0929 <SEP> m2)
<tb> anode <SEP> 4 <SEP> "<SEP> 25 <SEP>"
<tb> (in average <SEP>)
<tb>
 
 EMI18.9
 L2 effective density of the cournnt 4t? I.t of 8 amp. p'Or catté foot (0.092? rn2).

   L'8rRent dpos Fl ecti? Olj7tiaue.; Average pn r-u, of this electrolyte, by using the indicative current cyci p oeej aviit an extr <'Jordi1 "' i T'G:" S2: t Dnito. AUC11 "l 'olisS: '19 ci> ill8vl; -> gp.' 0éc <: enioue T1't" r? 1t '' 1CPSS7¯Te / t ,,,, nt rJonn / ave l'er; snt ftpit ussi brilliant that we could get it per n'inport9 ouel tr "'itel1 (' nt l: 1; cRniGue. Conmpr! .1tivRY11:, lt, l'2rent: e due to i'.11 usual direct current offered a -ppr'rpnce; ,, o: īns dump, unpleasant and Dlpte. The mrgeiJt film produced by the present invention 4tr'it eJ; cepts.c-nnel-1 st <irJ-t homogeneous , smooth and uniform The silver plating fa, '¯sawt USé' :: -: e dl) conrent the alternative of this invention would be tOl) t B ±> 1.t suitable for immediate use.

   L9 =? Annuity for do'nesti- uses

 <Desc / Clms Page number 19>

 and others of industry and commerce would be successfully obtained by the present process without requiring any mechanical polishing or other treatment.



   Many other cycles have been used for silver with equally good results. electroplating. For example, the duration was reduced from 10 to 30 seconds with a thermal current density of 15 amps. per square foot (0.0929 m2). The anode current densities increased from 50 to 150 amps per square foot (0.1929 m2) at most for time periods between 2.5 and 9 seconds. The densities of the anode current tend, with the silver, to decrease at the end of the periods. Silver plating can be accomplished by employing cathodic current densities as great as 100 amps per square foot (0.0929 m2).
 EMI19.1
 



  BXBgPLf VIII <
An aqueous solution for the gilding was prepared using the following essential elements:
 EMI19.2
 
<tb>
<tb> or <SEP> 0.51 <SEP> ounce <SEP> per <SEP> gallon <SEP> (14 <SEP> gr. <SEP> per <SEP> 3.78 <SEP> nit)
<tb>
 
 EMI19.3
 potassium cyanide, ssiw1J at native etaA 0.38 "(il fr. The current cycle used was:
 EMI19.4
 
<tb>
<tb> current <SEP> time <SEP> - <SEP>
<tb> cathode <SEP> 15 <SEP> seconds <SEP> '<SEP> 10 <SEP> amp. <SEP> by <SEP> foot <SEP> square <SEP> (0.0929 <SEP> m2)
<tb>
 
 EMI19.5
 . anode 2 Il 10 Il (") The effective current density was 3 amps
 EMI19.6
 per square foot (0.0929 m2).

   The gold was electrolytically deposited on a rectangular piece of rough sawn. '' Gold was far superior to any known gilding, by direct current, in both uniformity and coloring.



   The electrolytes of the preceding examples do not exhaust all the assumptions but are simple examples of the current invention. In many cases, the electrode 28 used in each solution was made of the same metal that was deposited. However, the electrode was one piece - inert, when gilding. We can perform 'electroplating A

 <Desc / Clms Page number 20>

 satisfactorily, according to this invention, whatever the nature of the anodes.
 EMI20.1
 



  To illustrate a further advance of the process of this invention, reference should be made to fig. 6 of the plan, which shows a rectangular piece 52 constituting a housing open at the ends. Part 52 is a common form of housing for enclosing apparatus and instruments. To cover parts identical or similar to niece 52, it was / formerly necessary to employ an anode inside.
 EMI20.2
 inside the frame 5 as well as the anodes around the inside of the frame. Even then, uneven f-electrolyte deposits often occurred.

   By the use of the reciprocating cycle of this invention, it has been found in possibility of electrolytic coating, absolutely uniformly, the two inner and outer surfaces of a part of cpdre 5, without using an anode. c1Uelconaue located inside or without. resort to other expedients that waste time. The copper plating of a corresponding sawn case
 EMI20.3
 to 18 room 5? a '') rodl1Í t a smooth and shiny coating on both the interior and exterior surfaces of the part, em-
 EMI20.4
 bending only outer anodes. The part was not expected to be so well plated with exterior anodes only.



   An important feature of the invention is
 EMI20.5
 tituée by the better distribution of <uàt> 1 1¯; cvf ', harm is provided by the alternating current cycle of this invention including the electroplating of the parts of figs. 5 and 6 gives a
 EMI20.6
 example. The densities of the electrolytic coil are usable even with parts of complicated surface, are much higher than would be possible by using direct current.
 EMI20.7
 



  The electrolytic deposits produced by the invention have mechanical as well as chemical properties superior to those of the coating produced by conventional methods.

 <Desc / Clms Page number 21>

   sics; they are therefore advantageous in many applications requiring the best properties obtainable for the electrolytically deposited metal. Automotive hardware, which is subject to friction and is exposed to moisture and noxious gases, can be successfully covered with a more durable and corrosion-resistant plating by the process of the present invention.

   It will be noted that domestic applications, subject to heating, to food acids and others. corrosive influences, will likely last longer, and with better results, if manufactured in the manner set forth herein. Polishing or mechanical grinding can be omitted in many cases, particularly in copper plating, silver plating and brass plating, given that the plated part will have been found to be as shiny as could be. obtain any mechanical polishing operation.

   Engraving dies, galvanos, molds for plastics and the like can be prepared, like parts of complicated shapes, by electrolytically coating with metal, according to the present invention, raw parts of graphite bodies. or carbon, wax or resin mother models, stamped with a surface conductive coating of graphite or metallic powder, to create a plating much more durable and much more wear resistant than this. which can be ensured by any known electroplating process. The plated metal will be much harder and more resistant to corrosion, under service conditions, than a metal deposited on a regular basis.

   The pattern will be followed faithfully without excessive overlap of corners and protrusions. We will therefore obtain printing plates and matrices of extended use.



   Regardless of the shape, size or use of the part, all electroplating operations should be successful when conducted with alternating current, following the teachings of the present invention.



  AT

 <Desc / Clms Page number 22>

 
The alternating current coating of the present invention can be practiced in any type of device or apparatus commonly used in electroplating.



  Rubber covered steel containers will generally be found to work well, although wood, glass or other materials can be used. The parts to be treated can be suspended from a fixed support or from a mobile conveyor. The size of the apparatus brought no difficulty. Alternating current cycle electroplating has been implemented equally effectively in small bare glass vessels in large vessels with capacity. several hundred gallons of electrolyte.



   It will be appreciated that alloys as well as simple metals can be electrolytically deposited by the present alternating current process. A single piece can be covered with several successive deposits of metal in any desired proportions.



   The electrolyte can be stirred or distributed according to well-known practices in electroplating. It has been found desirable to maintain a clean electrolyte, for example by filtering or a similar operation, since the electrolytic deposits have such a polished surface that any solid impurity, coming from the electrolyte and deposited on the plated work, is bea.ucoup more apparent than in ordinary electroplating. The temperature of the electrolyte can be changed to suit the requirements of the recovery. The current cycle works at both boiling water temperatures and below ambient temperatures.

** ATTENTION ** end of DESC field can contain start of CLMS **.


    

Claims (1)

R E V E N D I C A T 1 0 il 5 1) A process for the electrolytic deposition, on a blank, of a metal coming from an electrolyte, characterized by the inapplication of the electrolyte to the blank ;, by the <Desc / Clms Page number 23> passage of an electric current through the workpiece and through the electrolyte to make the workpiece cathodic for a predetermined period of time to electrolytically deposit metal thereon. the., blank '., by.the inversion of the current to make the blank anodic, .the current having such a density. that and being applied for a time sufficient for an electrolytically deposited, weak and low quality metal to be removed, the electrolytically deposited metal and not the raw part preferably being soluble in the electrolyte during the application of the reverse current, and repeating the current cycle until a predetermined thickness of pure metal has been electrolytically deposited on the part. 2) A method according to claim 1, characterized by applying a voltage to the blank for a period of time between about 2 and 40 seconds, and by not applying a reverse voltage for a period of time. between about 0.5 and 10 seconds. 3) A method according to claim 1 or 2, characterized by applying to the blank, during the recovery cycle, a periodically reversed electrical voltage. 4) A process according to. claim 1, 2 or 3, ca-. effected by the application to the part, raw of a periodically reversed electric voltage, so as to produce on the raw part an electroplating cathode current density at least 25% higher than that which can be applied effectively. especially when using a permanent direct current. 5) A method according to any preceding claim, characterized by applying to the blank, during the "displacement" cycle, a reverse current using at least 10% of Coulombs used for collection. 6) A method according to any preceding claim, characterized by passing the reverse current through the workpiece <Desc / Clms Page number 24> raw with a current density significantly greater than the density of the recovery current. 7) A method according to any preceding claim, for electrolytically coppering a blank, characterized by the inapplication to the blank of an aqueous alkaline electrolyte, one of the essential constituents of which is copper cyanide. 8) A method according to any preceding claim, for electrolytically brassing a raw part, characterized by applying to the raw part an aqueous alkaline electrolyte containing as essential ingredients copper cyanide and zinc cyanide. 9) A method according to any preceding claim, for electrolytically silvering a blank, characterized by 1-application to the blank of an aqueous alkaline electrolyte, one of the essential constituents of which is silver cyanide. 10) A blank electrolytically coated and manufactured according to the process according to any preceding claim. 11) The processes for electrolytic deposition, on a blank, of metal coming from an electrolyte, essentially described above and illustrated in the appended drawing. 12) Electrolytically deposited copper comprising a homogeneous mass composed of several successive layers of copper deposited in parallel and of microscopic thinness, the deposited copper having a higher density ;, a finer crystalline structure, a greater corrosion resistance and higher elasticity in copper electrolytically deposited by the use of permanent direct current alone. 13) Electrolytically deposited brass comprising a homogeneous and shiny mass composed of several successive layers, deposited in parallel and of microscopic thinness, of brass having a higher density, a crystal structure. <Desc / Clms Page number 25> line, thinner, greater corrosion resistance and higher elasticity than electrolytically deposited brass by the use of permanent direct current alone. 14) Silver deposited electrolytically and comprising a homogeneous and shiny mass composed of several successive layers, deposited in parallel and of microscopic thinness, of silver having a crystalline structure 'finer than' silver deposited electrolytically by the use of 'a permanent direct current alone.