US2315740A - Protected metal article and process of producing the same - Google Patents

Description

'ingofappreciable; g "Thebasemetalfromwhich'thearticlesjn- Patented Apr. 6, 1943 PROTECTED METAL ARTICLE AND PROCESS F PRODUCING THE SAME James M.

Schoonmaker,

Jr., Sewickley, and

Franklin Stockton, Goraopolis, Pa, assignors to Standard Steel Spring Company, Coraopolis, Pa., a corporation of Pennsylvania No Drawing. Application June 16, 1941,

Serial No. 398,338

Claims.

This invention relates generally to the protection of ferrous metals, such as are employed in the industrial arts, from the effects of such reagents as occasion corrosion and/or embrittlement.

Corrosion presents a serious problem inthe inindependently of the form in which the reagent exists An object of this invention is to provide a surface condition for ferrous metal articles which,

will resist deterioration occasioned by the active effect of contacting reagents.

Another object of the invention is to produce a surface coating for ferrous metal articles which will provide a satisfactory operative surface, such as a bearing or wearing surface, but which will, at the same time, resist the deteriorating effect occasioned by the action of such reagents as the article maybe exposed to during use.

A further object of the invention is to produce a metal article such, for example, as a rod, tank, delivery conduit, wire, forging, casting, bar, sheet, or other shape, which is formed of a base metal,

,such as steel, iron or a ferrous alloy, but which is provided with a surface or surface condition such as will occasion eifective resistance to the detericrating effect of such reagents as the article is' subjected to during its normal life.

.A specific object of the invention is to produce a surface condition on ordinary iron and steel articles which will resist the embrittling effect occasioned by such reagents as hydrogen, hydrogen sulphide, etc.

One aspect of the invention involves providing a ferrous metal article witha corrosive-resistant coating and then so treating the coated article resistant metal which is preferably employed in such minute quantities as, to avoid the producflan of a second coating'or at least a second coatmetal, such as iron, steel, or one of the commercial ferrous alloys. The first coating will ordinarily be deposited on the ferrous metal by an electrolytic or similar process and will ordinarily consist of a relatively thin coating of a metal, such, for example, as nickel, which is noble with respect to the base metal. Microscopic and other examinations of such coatings have disclosed that no matter how carefully applied, they are not impervious. That is,.they do not provide a uniform, unbroken coverage which extends throughout the entire extent of the suriaceof the article. On the other hand, such examinations have disclosed a pervious condition resulting possibly, orrat least in part, from porosity, but,

in any event, such as to render the base metal subject to attack at different points of its surface and even subject to the attack by such a mild corrosive agent as moist air.

In carrying forward our invention, we provide the surface of the base metal with a coating which is impervious to the passage of corrosive reagents. As above noted, this is accomplished by providing the base metal surface with a coating of corrosion-resistant metal and then by impregnating the coating metal with a metal which, at least in its final state, is resistant to the corrosive action of such reagents as may be encountered by the article during its commercial or industrial use.

A specific aspect of the invention is to produce an article, such, for example, as a' sucker rod, which is immune to or at least highly resistant to the action of such corrosive and embrittling as to impregnate the pores, interstices, and/or 'n inute crevices thereof with asecond corrosionwashing. The rod is then electroplated in an H -volvedare fabricateiwill be a ferrous) reagents as are likely to be encountered in well pumping 'operations. Sucker rods are composed essentially of ferrous metal and in use they are often subjected to the deteriorating effect of liquids which at least approximate theiaction of a. combined solution 'of sodium chloride and hydrogensulhhide.

In producing a sucker rod embodyingour in vention, a rod of the desired size, shape, etc. is made from a base metal such as steel and it is j subjectedto'such cleaning and preparatory operationsas are necessary or desirable as a "preliminary to electroplating. These operations may include, for example, sand blasting, pickling, and

salts, nevertheless it is desirable to employ thin coatings ranging from about one ten-thousandth of an inch to about four one-thousandths of an inch (.0001"-.O04") in thickness.

Nickel is a hard and substantially corrosionresistant metal having at least slightly more noble characteristics than the ferrous metal of which the rod is basically formed and the thin coating so produced is in itself a protection for the surface of the sucker rod. .The inherent porosity of thiscoating and the porosity and the surface crevices and interstices of the underlying base metal-favor attack by such reagents as the rod is ordinarily subjected to during use. That is to say, the condition of the sucker rod, even after having been plated with a non-corrosive coating such as pure nickel. is such as to permit rapid deterioration by reason of corrosion and embrittlement when the rod is subjected to corrosive and embrittiing reagents. The coated rod is, therefore, impregnated with a second corrosive-resistant metal which is preferably less noble than the base metal (ferrous metal) and is preferably capable of exerting an appreciable vapor pressure and producing the desired result when subjected to a definite degree of heat even at a temperature substantially below its melting point.

For conditions such as are encountered with sucker rods, zinc has disclosed itself to be an efifective impregnating metal.

The impregnation may be accomplished in a number of ways. For example, a thin coating of zinc may be deposited upon the nickel coated sucker rod after which the rod is heated under conditions such as to accomplish a zinc impregnation of the nickel coating and also of the .underlying surface of the base metal. The thickness of the zinc coating may vary and may be subject to modification to suit particular conditions, but a thin coating is preferred and highly satisfactory results have been accomplished with a zinc coating of less than lioooo of an inch thick.- This coating may be deposited upon the nickel either by electro-deposition or by a hot dipping process wherein the nickel coated sucker rod is submerged in a bath of molten zinc and maintained therein for an appreciable period or at least long enough to insure its receiving a substantially uniform coating of zinc. Where the sucker rod is subjected to a hot dipping, the Zinr coating is ordinarily thicker than is necessar:

peratures substantially above the melting point of zinc and it should here be noted that there is a temperature time relationship which is essential in order to obtain complete impregnation. For example, where an article, such as a nickel coated sucker rod is exteriorly uniformly heated throughout its length in an induction furnace and in a non-oxidizing or neutral atmosphere, a satisfactory impregnation may be obtained in a period of about ten minutes where the temperature of the rod is caused to approach 1800 F. Having in mind that the rod is comparatively cold at the beginning of the interval of ten minutes and that it does not reach its maximum temperature until the end of the ten minutes, it will be appreciated that the temperature of the rod is considerably belowv 1800 F. for a large portion of the ten minute interval. As lower temperatures are employed, the heating period is necessarily increased and for temperatures approximating from 350 F. to 400 F. the interval during which the article is maintained at that temperature should be extended to approximate- 1) three hours; additional time being, of course. required to bring the article up to that temperature. It will, however, be understood that this temperature time relationship also depends, for example, upon the character of the article involved, the character of the heating, the use to which the article is to be put, the size of the article, the thickness of the primary coating and/or the metal employed in the coating and/or the impregnating metal. Then too, where the article is suchas to quickly attain the desired temperature, conditions may indicate a heating time materially shorter than the time above stated, but on the other hand. certain articles and certainuses may indicate a much longer heating period and particularly where the lower temperatures are involved.

The articles produced by a procedure such as here outlined are substantially free from embrittlement or at least from a dangerous degree of embrittlement for an extensive period of time, and even where they are subjected to embrittling reagents such as are ordinarily encountered in oil well pumping operations.

After the heat treatment, the article may be cooled to atmospheric temperature.

While it is difiicult to precisely define what takes place during the impregnating heat treatment, such reactions as can be traced .by subseor desirable and the excess zinc may then be removed in any suitable manner.

Regardless of the particular manner in which the zinc coating is applied, the sucker rod is then subjected to a heat treatment carried on under conditions such as will insure complete impregnation of the nickel coating with zinc. The heating is preferably carried forward in a non-oxidizing atmosphere and under conditions such as to insure uniform heating of the sucker rod. This can be effectively accomplished in an induction furnace where the nickel coated articles are so placed that they lie within the magnetic field generated by the induction coils. The period necessary to bring the rods or coated articles up to the desired temperature will, of course,.vary with the size of the articles.

We have found that the impregnation occurs throughout a relatively wide temperature range. Where nickel is employed as the primary coating and zinc is employed as the impregnating metal, the temperature of this heat treatment may vary from temperatures as low as 300' I". to temamnity between the two metals involved. The

term mechanical aflinity. is employed to define an action comparable to ordinary capillary action which takes place when the impregnating metal is in a state or condition capable of responding to such an action. We assume that this takes place under conditions simulating capillary attraction and wherein the surface impregnated by the impregnating metal constitutes the capillary structure. Under such conditions it seems apparent that there is also a strong chemical affinity between the coating and the impregnating metals or that a condition is arrived at during the heating period where a combination of mechanical and chemical reactions result. One component of this combined reaction is an alloying of'the two metals involved and that this contributes to a chemical or metallurgical reaction and at the same time favors filling of the pores, interstices, etc. of the primary coating metal with the impregnating metal.

A sucker rod thus treated, i. e., provided with a primary coating of nickel and then subjected-to an impregnating heat treatment in the presence of metallic zinc, is rendered highly resistant both to the corrosive and embrittling effect of the water solutions of sodium chloride and hydrogen sulphide to which it is normally subjected in use. We have also found that even where the base metal from which the article is formed is metallurgically such as to be highly susceptible to embrittlement, the procedure will have an important and beneficial effect. Where the base metal is metallurgically such that it is normally somewhat resistant to embrittlement, the procedure herein set forth will protect against embrittlement such as is ordinarily occasioned by industrial uses wherein the article is either continuously or intermittently subjected to a highly active embrittling reagent.

After the heat treatment of a nickel, zinc coated article, such as the sucker rod, it will be found that the zinc coating has materially decreased in thickness and, depending upon the conditions of atmosphere is not essential during the heat treatment, although it is highly desirable.

Hi hly satisfactory results have been accomplished in impregnating nickel coated steel sheets I with zinc where the sheets'are arranged in pack formation with zinc sheets intervening between the nickel coated steel sheets. These packs are preferably heated in a reducing atmosphere and preferably to a temperature somewhat below the melting point of .zinc and for a time not only suflicient to occasion uniform heating of th pack, but also to accomplish the result. That is to say, the temperature time relationship heretofore Zmentioned, must be taken into consideration and the length of time must be suchas as compensate for the low temperature employed. a

The foregoing discloses that while it is not essential for the impregnating metal to be in intimate contact with the coated article at the initiation of the heat treatment, it is essential for the heat treatment to be carried on under conditions such that the article is subjected to direct contact with the impregnating metal as that metal passes through ;a condition approaching or approximating a' colloidal or jellyelike state.

A further consideration of the pack treatment of the nickel coated sheets discloses that the zinc sheets of the pack may be used over and over again and that the desired impregnation of the nickel coated ferrous sheets is accomplished even thoughv the'zi'nc' sheets are not materially r duced in weight and even though they are not in intimate contact with the nickel coated sheets throughout the entire surface of those sheets. From this it isapparent thatduring the heat treatment a portion of the zinc subjected to the heat treatment passes through a condition apis highly active as an impregnating medium for the nickel coated ferrous sheets. With this in mind, it is apparent that such articles as nickel coated sucker rods need not be coated with zinc prior to the impregnating heat treatment. The zinc may be introduced into the induction furnace in the form of zinc metal powder and this powder, may be conveniently supported onthe rod by means of an adhesive coating which is dissipated by the heat involved. Under such conditions the zinc powder undoubtedly passes through a condition simulating a vapor state and for that reason is effective as an impregnating medium.

All electroplating processes are poorly adapted for the corrosion proofing or coating of unpolished raw metal surfaces of such metals as steel. The trouble appears to be that the raw metal surface contains projections, recesses, pits, cracks, seams, and non-metallic inclusions, all of which have the tendency of interrupting the integrity of a protective coating. Then too, the electrolytic process itself favors the production of a coating of high porosity and one which is, therefore, not impervious to some reagents. Even so, no old procedure for protecting or producing a protective covering approximates the results accomplished by our new procedure in connection with corrosive and embrittling reagents.

A good continuous coating of zinc on iron will protect the iron from numerous forms of wet corrosion until the metallic zincbecomes dissipated or the integrity is interrupted. In some cases, the protection afforded by the zinc has subsisted until the zinc has wholly disappeared at least as a coating of appreciable thickness. Metallic zinc is considerably less noble and more anodic' than ferrous metal, such as iron or steel. In fact, it is far more anodic than is necessary for protective purposes and because of this it is too rapidly dissipated. Furthermore, a straight zinc'coating on iron or steel. or even a straight zinc coating applied over-a nickel coat on the iron or steel will permit exteriorly applied reagents to embrittle the iron or steel through the coating or coatings. Not only is this the case but the application of a straight zinc coating on nickel coated iron or steel seems to lower the re-. sistance to the action of embrittling reagents and will in itselfcause embrittlement of the iron or steel in numerous water solutions.

In the foregoing, the term straight zinc coating is used to distinguish from the application of zinc to the metal article in accordance with the procedure which is here involved in our invention. The nickel-zincor like compound resulting from the application of our invention to a metal article'is subdued and mild electrolytically, but is nevertheless sufliciently anodic and energetic.

with relation to such base metals as the ferrous metals, to form a substantially permanent protective coating for such metals. It endures many 7 times longer than straight zinc coatings and is many times more effective than pure nickel coatings.

Under certain conditions of application the advantageous results of our invention can be de- 41 I fined in terms of electrolytic action. That is to proximating a vapor state and inthis condition 'say, the metal-(for example, nickel) employed in the primary coating is slightly more noble (and preferably only slightly more noble) than the base'metal (iron, or such other base metal as is The heat treatment effects a combination such that there results in the surface of the treated article a degree of metal nobility and electrical potential that is approximately equal to that of the base metal, in at least some relations and for numerous sets of corrosive circumstances. Thus it is apparent that the coating, instead of being more noble and cathodic to the base metal (for example, iron) is slightly less noble and is anodic, to the base metal (iron) which is now cathodic, with the result that such slight diiTerence of potential as exists at the surface of the treated article is one in which the protective coating igslightly' anodic with relation to the coated metal.

For numerous commercial applications it is desirable to treat the coating resulting after the impregnating heat treatment with chemical reagents for the purpose of removing zinc or other oxides and most, if not all, of the free surface zinc or other impregnating metal. This can be done with acids and acid solutions and phosphoric acid salts and acetic acid are recommended for this purpose. It, however, may be noted that a cyanide solution (such as NaCN), Parkerizing and Bonderizing solutions may also be employed. This step of removing oxides and excess impregnating metal improves the appearance of the treated article and also, to some extent, improves its corrosion and embrittling resistance characteristics.

We shall now set forth some specific examples.

Example #1 of approximately six hours in a non-oxidizing atmosphere. The rod was found to be corrosion resistant to an appreciably marked degree.

Example #2 22 gauge steel strip was first cleaned by pickling. Thereafter it was electroplated with nickel to provide a coating .0002 of an inch in thickness. It was thereafter electroplated with zinc to provide a coating .0001 of an inch in thickness. Thestrip was then coiled up in coils and such coils were placed in an electric furnace. Starting cold, heat treatment was continued in a non-oxidizing atmosphere for a'total period of six hours. It took the first three hours to bring the furnace upto a temperature of 700 F'.- After this temperature was reached suchtemperature was maintained for a further period of three hours. The protected metal was'found to be corrosion resista product, so far as corrosion resistance was concerned, as the product of Example #2 above. This diminishing of the desired properties was apparently due to the employment of too high a degree of heat for too long a period.

Example #4 Ferrous screen cloth was first cleaned by pickling. It was then electroplated with nickel to provide a coating .00005 of an inch in thickness. Over this there was electroplated a layer of zinc .00015 of an inch in thickness. The plated wire cloth was then rolled up in rolls, each roll conant to a marked degree and suitable for use in spray tanks which in use are subject-to corrosion. Example #3 The same metal, electroplated with nickel and with zinc as explained in Example #2, was heat treated in an electricfurnace at a temperature which varied from a low of 700 to a maximum taining 300 feet of wire cloth. The rolls were then heat treated for a period of two and onequarter hours at 700 F. The resulting wire cloth was found to have corrosion resistant characteristics to a marked degree. In heat treating screen cloth excellent results have also been attained by merely passing the screen cloth around a roll or group of rolls. Screen cloth having the nickel and zinc coatings of the thicknesses mentioned above was heat treated by passing the cloth around two rolls which were heated to 700 F. The screen cloth was in intimate contact with the heated roll surfaces for an approximate peri- 0d of 45 seconds. When the screen cloth was coiled up and heat treated, the greater part of the relatively long heat treating period was required to bring the coiled material up to the temperature required for alloying the zinc with the nickel, whereas when the screen cloth was heat treated by direct contact with the heated roll, the cloth quickly reached the temperature of the roll and a relatively short period of forty-five seconds was suflicient to both raise the temperature of the cloth and cause the zinc to alloy with the nickel.

Example #5 Steel sheets .125 of an inch in thickness coated with nickel .002 of an inch in thickness were packed with interleaved thin sheets of pure zinc i. e. commercial rolled zinc). The cold pack was placed in a. furnace, the furnace temperature lieing 650 F. at the start and then raised to 710 F. and thereafter maintained at 770 E, which is somewhat below the melting point of zinc, for three hours. Satisfactory corrosion resisting coatings were obtained.

General example base. For example, a No. 9 steel wire having a coating thickness of .0003 of an inch of nickel and .0003 of an inch of zinc was heat treated by dipping in a heated salt bath. The best results were secured when the bath was maintained at a temperature of 1500- F. and when the wire was kept in the bath from two to five seconds, with the salt bath at 1300 F., thedipping period varled-between two and ten seconds and with the bath at ll00 F. the dipping period should be four to sixty seconds.

Experience with the foregoing products and examination and test of specimens and test pieces has demonstrated that the heat treatment causes the zinc or portions thereof to become alloyed with the underlying nickel coating. The extent to which alloying occurs varies in accordance with the thickness of the coatings and also in accordance with variations in the heat treatment. Alloying will vary from complete alloying extending through the nickel coating to partial alloying wherein there is a lower stratum or layer of nickel adjacent the ferrous base which is unalloyed with zinc having superimposed thereon an alloyed zone or zones of nickel and zinc. In some instances. unalloyed zinc is also present. While improved corrosion resisting characteristics are attained in all cases, present experience demonstrates that the best corrosion resisting characteristics are afforded when the alloying of the underlying nickel only extends part way through the nickel layer, leaving unalloyed nickel adjacent the ferrous base.

Microscopic examination of a typical nickelzinc alloy formed by carrying out the present process shows that the alloy has a stratified appearance, and analysis shows that the nickel and zinc, in what are for convenience termed the strata or layers of alloy, conforms in structure and composition to the well known nickel-zinc alloy system as follows:

Alpha Up to 28% Zn Beta (sub-one) 50-44% Ni Gamma prime f 24-20% Ni Gamma 20-13% Ni Delta 12-10% Ni veloped. By carrying out the process in the man- 45 ner heretofore described such conditions will be found to exist.

Due to the fact that the heat treatment is eflected at a temperature substantially below the melting point of nickel, the nickel layer is not alloyed with the underlying ferrous base but remains bonded thereto by what may be termed the "electrolytic bond" which is secured by the nickel plating step of the process.

Experience and tests have furthermore shown that desired impregnation and creation of the described nickel-zinc alloy or alloys may be attained when the heat treatment is effected at temperatures substantially below the melting point of zinc. Furthermore, by heat treating at such temperatures zinc losses are minimized.

When-nickel is plated on a ferrous base and heat treated, the alloying of the nickel with the iron will'depend on two factors, viz. the temperature and the time duration of heat treatment.

Substantially no appreciable alloying of the nickcl withthe iron base will take place when a large article such as a sucker rod, is placed in a fur-' nace and in about ten minutes is caused to approach a temperature of 1800 F. A greater part of the relatively short heating period is consumed in raising the temperature of the relatively massive cold rod and the rod itself-is not maintained heated above the nickel iron "alloying temperature (i. e. 1300 F.) for a long enough period proximating from two to six hour without substantial alloying of the nickel with the iron. No appreciable alloying of the ferrous base with the nickel layer will take place at temperatures below about 1300 F. Above that temperature, alloying of the ferrous base and the nickel will ocour only if they are held. at such elevated tem- -perature for a time interval longer than that necessary to cause the zinc to alloy satisfactorily with the nickel. According to the present invention the temperature-time relations of the heat treatment are .such that while there is alloying of the zinc with the nickel to a substantial and readily appreciable extent there is substantially no appreciable alloying of'the nickel with the underlying ferrous ,base.

The foregoing discloses that insofar as our invention involves procedure, an-important feature of the procedure is the impregnating heattreatment and the temperature-time relationship involved by that treatment. to set forth a rule for definitely defining this temperature-time relationship, it may be said that the heat treatment must continue for a time such that the articles treated are uniformly heated to substantially the temperature of the heat treatment and the impregnating metal is caused to pass through a condition approaching or approximating a colloidal or jelly-like state. If this rule is adhered to, it will be found that impregnation is satisfactorily accomplished.

While we have disclosed several modifications of the procedure herein involved as our invention, it will be apparent that other modifications may be made without departing from the spirit and scope of the invention and it will likewise be apparent that articles here defined as embodiments of the invention may be varied greatly within the contemplation of the invention as defined by the appended claims.-

This application is a continuation in part of our copending application Serial No. 237,924, filed October 31, 1938.

What we claim is:

1. The method of increasing the corrosion resistant characteristics of ferrous base metal articles, which comprise electroplating directly upon the ferrous base a coat of nickel, then electroplating the nickel coating with zinc, and then sealing the'pores resulting from electroplating by heat treating the composite electroplated article to a nickel zinc alloying temperature and under temperature-time relations at which there will be no substantial alloying of the nickel with ferrous base, to cause impregnation into the poles left by electroplating while maintaining the nickel' unalloyed with the ferrous base, and with the While it is difficultof the nickel with nickel-zinc alloy and leave; the ferrous:base unalloyed' with nickel and leave free zinc as.the exterior coating.

3. The method of protecting the surface of a ferrous article against corrosion which comprises electroplating directly upon the ferrous base. of

the. article a coat of nickel, depositing zinc upon the nickel coating to provide an intermediate article consistingof base metal coated with nickel in turn'coated with zinc as theoutermostrmetal llc layer,-heat treating thesaid intermediate article at a temperature above 300 F., preferably substantially below the melting point .of nickel,

to impregnate and alloy the outer portion of the nickel coating with zinc .while leaving the ferrous .ba'se unalloyeclv with the nickel.

jdfiThe rnethod of protecting. a ferrous meta article: against corrosionwhich .comprises. electroplatlngdirectly upon a ferrous base a coat of nickel, and sealing the pores of the nickel plate with'a nickel-zinc alloy :by heat treating the nickehplate in the presenceofzinc' alone ata temperature above 300 F. and preferably somewhat below the meltingpoin't of zinc to impregthe pores remaining after electroplating, while maintaining the" nickel unalloyed with. the

-ferro'us:base. l

base unalloyed with the nickel, and with the 'zinc' alloyed only-with the'nlckel.

6. A corrosion-resisting article comprising a base of ferrous'materlal havinga-layer of nickel electroplated directly-thereon,the vpores remain ing after electroplating being sealed by complete impregnation with an alloy consisting of 1 nickel and zinc, the nickel being electrolytically bonded to the ferrous base material but unalloyed there with, the outermost strata of said article including only nickel and zinc.

somewhatbelow the melting point of zinc, and

'l. A corrosion-resisting article comprising a V ferrous base having a nickel coat electroplated directly thereon and unalloyed to the ferrous base, a zinccoat on the nickel alloyed-thereto and a substantially pure unalloyed zinc outer surface.

8. The method of producing a corrosion-resisting outer coating on" a ferrous base which consists in electro-depositing a dense uniform coating-of nickel of a thickness within the range of 0.001 and 0.004 'of an inch directly thereon,

in electrodepositing a dense uniform coating of nickel directly onto said base of a thickness within the range of .0001 and .004 of an inch, then electrodepositing'directly on said nickel coating a coating of zinc less than .0001 of an inch in thickness, and finally. heating said composite in ,a non-oxidizing atmosphere to a temperature within the range of 300 to 400 F. for a time sufiicientonly to impregnate and permeate the .pores of the nickel coating and leave free zinc on the exterior surface thereof.

10. The. method of" producing a corrosion resisting coating on ferrous base screen cloth which'consists in'electrodepositin'g a dense uniform coating of nickel directly onto said ferrous ba's'e screen cloth, said nickel coating having a thickness of not more than .00005 'of which then electrodepositlng directly on said nickel coating a coating of zinc of not more than .00015 of an inch in thickness, and finally heat treating said composite article by passing said composite screen-cloth over rolls heated to approximately 700 F5; thescreen cloth being in contact with said heated rolls for a period of approximately 45 seconds to thereby impregnate and permeate the pores of the nickel coating and leave free zinc on the exterior surface of the article.

JAMES M. SCHOO'NMAKER, JR. mam s'rocrcrou.

CERTIFIEAT'E' 0F conmzc'non.

I Patent umjzgl uo. 'April 6, 199.

Jmss m. scnoonfikmn, JR., ET At.

It is hraby certified thaterror appeai-s in the printed specif-icatioh of the abovenu .mberedpatent requiring correotiofigs follows; ?age 5, first column, 11ne52, for 9s" sfd'bnd ocburrexi'ce, read ----topage 6, second 001m, 11 8 9, claim 8,; fQr 10.001" read --p.ooo1 ,--j that the said Bettara Psi tent should be regii with .thi-a'correctidn' ther ein that the game may confo mr t8 the "reco rd of. t l'i e case in the Patofit Officm' Signed arid gealed this 18th day of nay, A. D. 1%}.

Y Henry V'a n Arsdalg, 7 (Seal) 1 Aqtiii'g cominissibner of Patents.