US3537960A - Method of producing reinforcements in electro-deposits - Google Patents

Description

Nov. 3, 1970 c. H. ESOLA ET AL 3,537,960

METHOD OF PRODUCING REINFORCEMENTS IN ELECTRO-DEPOSITS Filed Dec. 6, 1968 INVENTOR. CHARLES H. EsoLA,

DONALD 6. KRE/TZ, Ham/v Irv/(W AGENT United States Patent O 3,537,960 METHOD OF PRODUCING REINFORCEMENTS IN ELECTRO-DEPOSITS Charles H. Esola, Springfield, and Donald B. Kreitz, Allentown, Pa., assignors to General Electric Company, a corporation of New York Filed Dec. 6, 1968, Ser. No. 781,862

Int. 01. C23b 5/48 U.S. Cl. 204-16 6 Claims ABSTRACT OF THE DISCLOSURE CROSS-REFERENCE TO RELATED APPLICATION Ser. No. 718,925, filed Apr. 4, 1968, by Charles H. Esola for Improvement in Electroplating.

BACKGROUND OF THE INVENTION Field of the invention This invention pertains to the field of electroplating.

Description of the prior art The incorporation of solid inclusions in electroplated coatings has been accomplished in the past by suspending the solids in the electroplating bath, usually by stirring the bath or otherwise maintaining a circulation of the bath to keep the solids in suspension. Alternatively, the substrate to be plated may be located with its major surface approximately horizontal so that the solids merely lie by gravity upon the surface, and become included in the course of the plating process. The first method suffers from the disadvantage that the same circulation which keeps the solids suspended tends to carry them away from the substrate before they become attached to it by the deposition of the plated coating, and the second method has the disadvantage that any foreign matter entering or formed (such as sludge) in the bath will fall upon the substrate. The magnitude of this latter disadvantage is indicated by the practice of electroplaters in general of placing work to be plated upon supports which maintain it clear of the bottom of the plating tank.

SUMMARY OF THE INVENTION In the copending application of reference it is taught to prepare a substrate for electroplating with aluminum by cleaning the substrate with aqueous solutions, and then rinsing away the aqueous material with a solution of oleic acid in isopropyl alcohol. While still covered with the fatty acid solution, the substrate is immersed in an aluminum plating bath which is a solution in organic solvents, e.g., diethyl ether. The bath solvent dissolves away the fatty acid coating, permitting plating.

We have observed that the fatty acid solution coated upon the substrate is sufficiently sticky that reinforcing fibers such as fine silica fibers, needle-like crystals of alumina or spinel (known in the art as whiskers), graphite fibers, or other insoluble material Which may for example be of high tensile strength and thus valuable as a reinforcement when occluded, may be deposited upon the coated substrate and will adhere to it. A substrate so coated is then immersed in the plating bath, and a high Patented Nov. 3, 1970 current density is immediately applied in order to produce an initial deposit as rapidly as possible, in order to tack the fibers to the substrate before the fatty acid coating is completely removed by the plating bath solvents. Presumably, the coating is removed locally at points where deposition occurs, while coating remains at other points long enough to retain the fibers until the tacking operation is sufficiently advanced to hold the fibers. When this stage has been reached, the current density may be adjusted to values appropriate to producing the desired deposition, and plating is continued until the requisite plating thickness has been produced. The reinforcements are embedded in the plated coating.

Since the application of the inclusions to the adherently coated substrate is a purely mechanical one, the particular orientation of the fibers may be controlled at will; their density at different parts of the surface may be varied arbitrarily up to the point where they are so dense as to preclude the contact of further additions with the substrate; mixed inclusions of differing densities may be applied without danger of segregation such as would tend to occur in any process in which the inclusions were suspended in a circulating plating bath. Also (a point of importance if the inclusions are expensive, as some of the high-strength fibers tend to be) the utilization of the fibers is very efficient; one is not left after the operation with a large quantity of unused fibers to be recovered from a spent bath. Since the efficiency of utilization is high, the proportion of fibers (or other inclusions) actually included in the product is better controllable, since there is no need to add a large excess of material which will remain in the bath in a difiicultly predictable amount.

The objects we achieve are thus, in general, the provision of inclusions in a plated deposit with high efficiency of utilization of the supply of inclusions, with generally predetermined orientation of the inclusions, and generally predetermined density of the inclusion distribution.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 represents a substrate according to our invention, coated with fibers;

FIG. 2 represents a conventional plating arrangement in which the substrate is being plated; and

FIG. 3 represents partly cut away a plated product.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 represents a substrate 10 which may conveniently be of aluminum or aluminum-base alloy. Substrate 10 may be cleaned by conventional means'to remove grease or other deposits, and then rinsed with a solution of equal parts of water and concentrated hydrochloric acid. This solution is in turn rinsed off with a solution of 60 percent by weight of oleic acid in isopropyl alcohol, the material adhering after the final rinse being allowed to dry in air until it becomes somewhat tacky from the evaporation of the alcohol. Alternatively, concentrated oleic acid may be applied without a solvent and heated in an air circulating oven until it becomes somewhat viscous. Inclusions 12, which are represented as fibers since fiberreinforced metals have a known utility as light-weight structural materials, are then applied to the tacky surface. This may be done, e.g., by shaking them from a fiat scoop. If necessary, they may then be pressed to the adhesive coating by a clean flat spatula to insure their retention. Any excess or loose fibers are shaken off, and the substrate is immersed in a plating bath, as represented in FIG. 2.

FIG. 2 represents an enclosed Vessel 14, with cover 16 and a source of inert gas 18 connected to provide an inert atmosphere over the bath 20, excess being vented through 21. Bath 20 may be an aluminum plating bath according to the teachings of Brenner et al. in US. Pat. 2,651,608. An anode 22 and the support 24 for the substrate are represented connected to a conventional plating current supply 26, represented simply by a rectangle. Immediately upon immersion, a plating current of density from about 60 to 120 amperes per square foot is applied for O.25-1.0 minute. This high current density produces tacking of the fibers, and the current density may then be reduced to a value better suited to build up the deposit 28 to the desired thickness. During the plating process the bath 20 dissolves the oleic acid and any isopropyl alcohol still retained by the oleic acid. Upon completion of the plating to the desired thickness the substrate 10, hearing the deposit 28 with the fibers 12 embedded in it, is removed from the bath and washed to remove the bath residue and dried.

The same basic method may be used more readily in conventional aqueous baths, since there are many water soluble adhesives which have long been known to be desirable addition agents for producing desirably fine-grained electroplated deposits. Alexanders Colloid Chemistry, D. van Nostrand Company, at page 190 of the third edition, published in 1929, mentions this fact, and cites specifically Mueller and Bahntje, Zeitschrift fuer Elektrochemie, 1906, vol. 12, page 317, for the fact that gelatin and egg albumin actually produce a slightly denser electrodeposit of copper than occurs in the same plating bath in their absence. An adhesive coating of gelatine may be applied to the workpiece and used to retain inclusions applied to it during strike plating precisely as in the previous example.

If it is desired to provide more than one layer of inclusions, a plated deposit containing a first layer of inclusions, produced as above described, may itself be used as a substrate for repetition of the process by applying to another layer of inclusions and plating upon that layer. This process may be repeated as often as required to build up a deposit with as many layers of inclusions as required.

The plated deposit with its inclusions may be used as a deposit upon the original substrate, or alternatively, it may be stripped from the original substrate in accordance with the known art and itself constitute the product of the process, being a reinforced metal capable of high tensile strength.

What is claimed is:

1. The method of forming an electroplated deposit containing inclusions which comprises the steps of:

(a) applying to a metal substrate a coating of an adhesive material which is soluble in an electroplating bath;

(b) depositing upon the substrate so coated a layer of inclusion material to be included as inclusions in an electroplated deposit;

(c) immersing the said substrate in the said electroplating bath;

(d) immediately after the said immersion applying a high density of plating current to the said substrate to affix the said inclusion material to the said substrate by plating metal from the said electroplating bath upon the said substrate;

(e) adjusting the density of the plating current to a value suited to the deposition of an electroplated deposit from the said electroplating bath, and plating upon the said substrate and around the said inclusion material an electroplated deposit.

2. The method claimed in claim 1 in which (a) the said adhesive material comprises a fatty acid;

(b) the said electroplating bath is a solution comprising an organic solvent.

3. The method claimed in claim 2 in which the said fatty acid is oleic acid.

4. The method claimed in claim 2 in which the said organic solvent is diethyl ether.

5. The method claimed in claim 2 in which the said electroplating bath is adapted to electroplate aluminum.

6. The method claimed in claim 5 dependent on claim 1, in which the high density of plating current recited in claim 1 has a value of at least amperes per square foot and not greater than amperes per square foot.

References Cited UNITED STATES PATENTS 3,441,487 4/1969 Rea et al 20416 FOREIGN PATENTS 602,099 7/ 1960' Canada.

1,048,934 11/1966 Great Britain.

ROBERT K.- MIHALEK, Primary Examiner T. TUFARIELLO, Assistant Examiner

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