US2457060A - Method for bonding a nickel electrodeposit to a nickel surface - Google Patents

Description

Patented Dec. 21, 1948 METHOD FOR BONDING A NICKEL ELEC- TRODEPOSIT To A NICKEL SURFACE Ralph Crysler Mcquire, Port Colborne, Ontario, Canada, assignor to The International Nickel Company, Inc., New York, N. Y., a corporation of Delaware No Drawing. Application December 18, 1945, Se-

rial No. 635,775. In Canada October 25, 1945 13 Claims.

The present invention relates to the treatment oi a nickel starting sheet or other nickel surface in order to insure adherence thereto of a subsequent nickel electroplating and to the product obtained by such treatments.

The art has recognized the broad problem of securing satisfactory adherence or bonding between a nickel surface and a nickel electro-plating. For example, U. S. Patent No. 2,001,385 discloses certain attempts which have been made in the art, such as the immersion of a nickel starting sheet in a dilute acid solution without application of electric current. An important feature of the process in U. S. Patent No. 2,001,385 is immersion of the starting sheet in the dilute acid bath for several hours. Another U. S. patent, No. 2,299,054, discloses the anodic treatment of a nickel starting sheet in a sodium cyanide solution to remove oxide film adhering thereto; the process disclosed therein also involves a cathodic treatment in the same cyanide solution prior to the electro-deposition of nickel. I am aware that other processes have been proposed and attempted for the cleansing and activation of other metal bases, for example, iron, prior to the electrodeposition of a metal plating thereon. However, none of these proposals and attempts has provided a satisfactory solution to the problem of securing an adequate bond between a nickel surface and a nickel electro-plating. This will be readily recognized by reference to an article by Pinner, Soderberg and Baker in Modern Electroplating, 1942, page 237, in which the authors point out the difiiculty in obtaining a good bond between a ductile nickel coating and a relatively thin, brittle coating deposited from a high sulfate nickel bath.

1' have discovered a commercially feasible process for securing adequate bonding between a nickel surface and a nickel plating subsequently applied thereto. My novel process is well adapted to commercial production due to relatively short working time and great economy in the use of treating reagents.

It is an object of the present invention to provide a process for securing adequate bonding between a nickel surface and a nickel electroplating. 1

It is within the purview of the present invention to provide an electro-deposited nickel cathode integral with and securely bonded to a nickel starting sheet.

The present invention further aims to secure a high degree of economy by providing for periodie recovery of certain of the reagents used in the bonding process.

The present invention further contemplates the provision of a plurality of coherent, bonded layers of electro-deposited nickel upon a metal article.

The scope of the present invention likewise includes the removal of a passive film from a nickel surface prior to the electro-deposition of nickel thereon.

Various other objects, advantages and features of the present invention will become apparent from the following description.

Broadly speaking, the present invention involves anodic treatment of a nickel surface in an aqueous chloride-bearing acid bath containing a significant concentration of cupric ions. An important advantage of the present invention is that adequate bonding between a nickel electroplating and a nickel surface can be obtained when the nickel surface is anodically treated in the chloride-bearing, cupric ion-containing bath over a wide range of current density, such as from about 5 amperes per square root to at least about amperes per square foot. Although current densities exceeding 150 amperes per square foot may be employed in carrying out the present invention, the present invention has particular advantage in that highly satisfactory treatment of a nickel surface is obtained by employing current densities of less than 150 amperes per square root. Thus, it is preferable, in carrying out the present invention to employa current density within the range of about 5 amperes per square foot to about 25 amperes per square foot. After the anodic treatment, the nickel surface is immediately given a water rinse and immersed in a nickel plating tank. in which a nickel plating is deposited upon and securely bonded to the anodically treated nickel surface.

I have observed that copper is deposited in sponge form at the cathode during anodic treatment of the nickel. in order to maintain an adequate concentration of cupric ion in the bath, I prefer to interrupt the anodic treatment at intervals and Pass compressed air through the bath whereby the sponge copper is redissolved. In this manner, I secure a high degree of economy in operation. Another method that may be employed to maintain the desired concentration of cupric ion in the bath is to add to the bath, at a controlled rate, a copper solution having a controlled composition. Thus, in this manner, the cupric ion content of the bath may be maintained within the desired range by replacement of the copper being removed at the cathode without interruption of the current.

In accordance with the invention, the nickel surface to be treated is immersed as anode in an acid treating bath containing a significant concentration of cupric ions. As previously 3 pointed out, the nickel surface may be a nickel starting sheet on which nickel is deposited, the resulting cathodic electro-deposit being suitable for subsequent use as an anode in a plating bath. n the other hand, in many cases it is desirable to deposit a nickel plating upon a previously nickel upon which it is desired to deposit a nickel plating.

The composition of the bath has an important effect particularly upon the character of the bond between the nickel surface, and the subsequently applied nickel plating. The chloride-bearing bath employed by the present invention should contain a concentrationof about 9.0 to about 195 grams per liter of chloride ion. Thus, adequate bonding between a nickel surface and a subsequently applied nickel plating is obtained when the nickel surface is treated in a bath containing about 50 to about 200 grams per liter of sulfuric acid and chloride anions in amounts equivalent to about 50 to about 60 grams per liter of sodium chloride. I prefer to employ sodium chloride as the source of chloride anions in the bath but it should be understood that an equivalent quantity of chloride ions can be added by the use of other suitable water soluble sources of such ions as, for example, potassium chloride, magnesium chloride, hydrochloric acid, etc. Satisfactory results are also obtained by employing a chloride-bearing bath that does not contain sulfate ions. Thus,

drochloric acid.

In accordance with the present invention, about a 0.5 to about grams per liter of cupric ion in the form of any suitable water soluble source of copper ion is added to any one of the acid baths previously described. However, the preferred range of cupric ion concentration is from about 2 to about 10 grams per liter. The presence of the requisite quantity of cupric ion is essential if proper bonding of the nickel surface to the subsequently applied nickel electro-deposit is to be obtained. In the absence of cupric ion in the bath, a dark thin sludge is formed upon the nickel surface and satisfactory adherence of a subsequent nickel plating to the nickel surface is not obtained.

' The nickel surface to be treated is immersed as anode in a treating bath having the aforedescribed composition. A current density of about 5 to at least about 150 amperes per square foot, as hereinbefore stated, is employed during the treatment of the nickel surface in the chloride-bearing bath. A current density below 5 amperes per square foot can be used and satisfactory bonding properties of'the nickel surfaces obtained, but it is preferred that at least 5 amperes per square foot be employed as a lower current density prolongs the time of treatment and is accordingly, uneconomical.

In view of the relatively close position of iron and nickel in the electromotive series, and their position in the periodic table. it would generally be expected that the present invention would also be applicable to treatment of iron surfaces. However, I have determined that iron surfaces cannot be satisfactorily treated at current densities below 150 amperes per square foot whereas nickel sur faces are satisfactorily treated at such current densities. These results indicate a marked difference in the anodic behaviour of iron and nickel which is not apparent from the relative position of these two elements in the electromotive series.

vFor best results, the treatment bath should be maintained at a temperature of about 60 to about F. However, the temperature is not critical and higher or lower temperatures than 100 and 60 F. respectively may be utilized.

The voltages required in the operation of the process vary with electrode spacing and current density. Preferably, the anode to cathode spacing is about 3 inches and a tank voltage of about 2 to about 8 volts is required. It is necessary to use the higher voltages in the baths containing a relatively large portion of sulfate anions whereas the lower voltages may be used with electrolytes containing a substantial proportion of chloride anions, as these have a tendency to improve the conductivity of the solution. Agitation of the bath has little or no effect upon the operation of the process and, accordingly, is not used in order to reduce the cost of the treatment.

The nickel surface is treated anodically for at least about 2 minutes; an anodic treatment for about 5 minutes has been found to produce the improved results contemplated by the present invention. A longer period of treatment than 5 minutes may be used but entirely satisfactory'results are obtained with a time of treatmentof about 2 to about 5 minutes. The treated nickel surface is removed from the bath and given a water rinse immediately after the anodic treatment is ended. It is important that the nickel plating be applied to the nickel surface almost immediately after the water rinse. Thus, the nickel plating is applied not more than about 60 minutes after removal of the treated surface from the rinse tank. In the event that it is not desired to apply the nickel plating within this period, the

, nickel surface should be kept immersed in a bath which will prevent the formation of a passive film onthe nickel surface. Thus, the nickel surface may be immersed in a bath of clear water.

Otherwise, satisfactory bonding of the treated nickel surface to the electro-deposit of nickel is not obtained due to formation of a passive film on the treated nickel surface.

During the operation of the process employed by the present invention for anodic treatment of the nickel surfaces, copper deposits in sponge form at the cathode, which cathode m; y be formed from nickel or any other suitable metal. In addition, a certain amount of nickel is dissolved from the nickel surface. Accordingly, the nickel content of the solution rises and the copper content decreases as the operation proceeds. When sufficient copper is deposited to lower the concentration of cupric ions in the bath to about 2 grams per liter, the anodic treatments are discontinued and compressed air is blown through the solution with the result that the copper is redissolved from the cathode and once more enters the solution, thereby maintaining a minimum concentration of about 2 grams per liter of cupric ion in the bath at all times. A nickel concentration of as high as 60 grams per liter does not interfere with the operation of my novel anodic treatment bath. However, when a nickel concentration of about 50 grams per liter is attained, I prefer to treat the solution in any suitable manner for nickel recovery. In this manner, great economy in the use of copper salts and recovery of nickel is obtained.

The following illustrative examples are provided in order that one skilled in the art may have a better understanding of practicing the present invention.

Example I A nickel starting sheet was immersed as anode in a bath containing about 100 grams per liter of sulfuric acid, about 50 grams per liter of sodium chloride and about grams per liter of cupric ion in the form of copper sulfate. Anodic treatment was carried out for about 5 minutes at a temperature of about 80 F. and at a current density of about 15 amperes per square foot. After the anodic treatment was completed, the starting sheet was removed from the bath and given a water rinse. From the rinse tank, the starting sheet was immediately transferred to a nickel plating tank and nickel was plated thereon from a conventional Watts-type bath until a deposit about 0.25 inch thick was obtained on each side of the starting sheet, giving a total deposit of 0.5 inch. The cathodic electro-deposit was removed from the plating tank and the degree of bonding between the nickel starting sheet and the nickel plate was tested. An entirely satisfactory degree of adhesion was obtained between the nickel starting sheet and the nickel electrodeposit, as no evidence of separation at the bond was observed when the following test was applied: a strip six inches long and one inch wide was cut from the cathode comprising the nickel starting sheet on both sides of which a thick nickel electro-plating of 0.25 inch was deposited. The edges of the cut strip were ground and etched to reveal the bond. The strip was then given a sharp right angle bend and the bond examined microscopically at a magnification of 1001:. Adhesion was considered satisfactory if no separation of the nickel electro-plating from the nickel surface occurred. In cases wherein faulty adhesion results due to improper treatment of the nickel surface, the defect is not always noticeable after the grinding and etching operation, but evidence of separation at the bond is observed after application of the stress due to bending.

Example II An iron article having a nickel plating thereon was anodically treated in a bath containing about 100 grams per liter of hydrochloric acid and about 5 grams per liter of cupric ion in the form of cupric chloride. The anodic treatment was continued for about 5 minutes employing a temperature of about 80 F. and a current density of about 15 amperes per square foot. Upon completion of this period of anodic treatment, the nickel plated article was removed from the bath and given a water rinse after which it was immersed in a Watts plating solution as cathode and a second deposit of nickel plated thereon. An entirely satisfactory adherence of the two nickel platings was observed and the second nickel plating had substantially no tendency to strip or peel from the first nickel plating.

Although various concentration ranges for the reagents used in my novel process have been set forth in the foregoing description, it is to be understood that the invention is not to be limited to these specific ranges, particularly with regard to sulfuric acid, hydrochloric acid and sodium chloride. Thus, for example, the preferred lower amount of hydrochloric acid concentration set forth for an all-hydrochloric acid bath is about 50 grams per liter. It will be appreciated that the acid concentration decreases as the bath is used due to hydrogen ion discharge at the cathode. Accordingly, the initial concentration should be at least about 50 grams per liter to maintain sufllcient acidity until the nickel concentration reaches about 50 grams per liter at which time it is preferred that the bath be treated for nickel recovery. However, a smaller initial concentration than 50 grams per liter of hydrochloric acid may be used if the bath is to be treated for nickel recovery before a nickel ion concentration of about 50 grams per liter is attained. Although an upper amount of about 200 grams per liter of hydrochloric acid concentration was chosen for economic reasons, greater concentrations could be used without departing from the spirit and scope of the invention. The concentration of chloride anions may also vary above or below the preferred range of such anion equivalent to about 50 to about 60 grams per liter of sodium chloride; the stated range of chloride anion equivalent to about 50 to about 60 grams per liter of sodium chloride having been found to give the maximum advantage of the chloride ion.

Although the present invention has been described in conjunction with certain preferred embodiments, it is to. be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention as those skilled in the art will readily understand. Such variations and modifications are to be considered to be within the purview of the present invention and the scope of the. ap pended claims.

I claim:

1. A method for obtaining improved bonding of a nickel electro-deposit to an articlehaving a nickel surface which comprises anodically treating said article having said nickel surface for about 5 minutes in an aqueous chloride-bearing bath consisting of about 50 to about 200 grams per liter of sulfuric acid, about 50 to about .60 grams per liter of sodium chloride, copper sulfate in an amount to provide a cupric ion concentration of about 5 grams per liter of cupric ion, and the balance essentially water at a current density of about 15 amperes per square foot; removing said article from said bath; rinsing said article; transferring said article to a nickel electroplating bath; and electro-depositing nickel on the anodically treated nickel surface of said article where by an improved bonding of a nickel electrodeposit to said treated nickel surface of said article is obtained.

2. A method for obtaining improved bonding of a nickel electro-deposit to an article having a nickel surface which comprises anodically treating said article having said nickel surface for about 5 minutes in an aqueous chloride-bearing bath consisting of about 50 to about 200 grams per liter of hydrochloric acid, cupric chloride in an amount to provide a cupric ion concentration of about 5 grams per liter of cupric ion, and the balance essentially water at a current density of about 15 amperes per square foot; removing said article from said bath; rinsing said article; transferring said article to a nickel electroplating bath; and electro-depositing nickel on the anodically treated nickel surface of said article whereby an improved bonding of a nickel electroaeeaoec deposit to said treated nickel surface of said article is obtained.

3. A method for obtaining improved bonding of a nickel electro-deposit to an article havin a nickel surface which comprises anodically treating said article having said nickel surface for about minutes in an aqueous chloride-bearing bath consisting of about 100 grams per liter of sulfuric acid, about 50 grams per liter of sodium chloride, copper sulfate in an amount'to provide a cupric ion concentration of about 5 grams per liter of cupric ion, and the balance essentially water at a current density of about -15 amperes per square foot; removing said article having said anodically treated nickel surface from said bath; rinsing said anodically treated nickel surface of said article with water; immersing said article having said anodically treated nickel surface in a nickel electro-plating bath and electrodepositing nickel on said anodically treated nickel surface of said article whereby an improved bonding of a nickel electro-deposit to said treated nickel surface of said article is obtained.

a. A method for obtaining improved bonding of a nickel electro-deposit to an article having a nickel surface which comprises anodically treating said article having said nickel surface for about 5 minutes in an aqueous chloride-bearin bath consisting of about 100 grams per liter of hydrochloric acid, cupric chloride in an amount to provide a cupric ion concentration of about 5 grams per liter of cupric ion, and the balance essentially water at a current density of about 15 amperes per square foot; removing said article having said anodically treated nickel surface from said bath; rinsing said anodically treated nickel surface of said article with water; immersing said article having said anodically treated nickel surface in a nickel electro-plating bath and electro-depositing nickel on said anodically treated nickel surface of said article whereby an improved bonding of a nickel electro-deposit to said treated nickel surface of said article is obtained.

5. A method for obtaining improved bonding of a nickel electro-deposit to an article having a nickel surface which comprises anodically treating said article having said nickel surface for about 2 to about 5 minutes in an aqueous chloride-bearing acid bath consisting of cupric chloride in an amount to provide a cupric ion concentration of about 2 to about grams per liter of cupric ion in said bath, hydrochloric acid in an amount to provide a total chloride ion concentration in said bath of about 9 to about 195 grams per liter of chloride ion, and the balance essentially water at current densities of about5 to about 25 amperes per square foot; removing said article from said bath; rinsing said article; transferring said article to a nickel electroplating bath; and electro-depositing nickel on the anodically treated nickel surface of said article whereby an improved bonding of a nickel electro-de posit to said treated nickel surface of said article is obtained,

6. A method for obtaining improved bonding of a nickel electro-deposit to an article having a nickel surface which comprises anodically treating said article having said nickel surface for about 2 to about 5 minutes in an aqueous chloride-bearing acid bath consisting of copper sulfate in an amount to provide a cupric ion concentration of about 2 to about 10 grams per liter of cupric ion in said bath, sodium chloride in an amount to provide a chloride ion concentration of about 9 to about 195 grams per liter of chloride ion in said bath, about 50 to about 200 grams per liter of sulfuric acid, and the balance essentially water at current densities of about 5 to about 25 amperes per square foot; removing said article from said bath; rinsing said article; transferring said article to a nickel electroplating bath; and c-lectro-depositing nickel on the anodically treated nickel surface of said article whereby an improved bonding of a nickel electro-deposit to said treated nickel surface of said article is obtained.-

7. A method for obtaining improved bonding of a nickel electrodeposit to an article having a nickel surface which comprises anodically treating said article having said nickel surface for about 2 to about 5 minutes in an aqueous chloride-bearing acid bath containing copper sulfate in an amount to provide a cupric ion concentration of about 0.5 to about 30 grams per liter of cupric ion in said bath; a chloride compound from the group consisting of hydrochloric acid, sodium chloride, potassium chloride and magnesium chloride to provide a chloride ion concentration of about 9 to about 195 grains perv liter of chloride ion in said bath; about 50 to about 200 grams per liter of sulfuric acid; and the balance essentially water at current densities of about 5 to about 150 amperes per square foot; removing said article from said bath; rinsing said article; transferring said article to a nickel electroplating bath; and electrodepositing nickel on the anodically treated nickel surface of said article whereby an improved bonding of a nickel electrodeposit to said treated nickel surface of said article is obtained.

8. A method for obtaining improved bonding of a nickel electrodeposit to an article, having a nickel surface which comprises anodically treat ring said article having said nickel surface for about 2 to about 5 minutes in an aqueous chloride-bearing acid bath containing a water-soluble copper compound to provide a cupric ion concentration of about 0.5 to about 30 grams per liter of cupric ion in said bath; a chloride compound from the group consisting of hydrochloric acid,

sodium chloride, potassium chloride andmagnasium chloride to provide a chloride ion concentration of about 9 to about 195 grams per liter of chloride ion in said bath; about 50 to about 200 grams per liter of sulfuric acid; and the balance essentially water at current densities of about 5 to about amperes per square foot; removing said article from said bath; rinsing said article; transferring said article to a nickel electroplating bath; and electrodepositing nickel on the anodically treated nickel surface of said article whereby an improved bonding of a nickel electrodeposit to said treated nickel surface of said article is obtained.

9. A method for obtaining improved bonding of a nickel electrodeposit to an article having a nickel surface which comprises anodically treating said article having said nickel surface for about 2 to about 5 minutes in an aqueous chloride-bearing acid oath containing a water-soluble source of cupric ions from the group consisting of copper sulfate and cupric chloride to provide a cupric ion concentration of about 0.5 to about 30 grams per liter of cuprlc ion in said bath; a

chloride compound from the group consisting of hydrochloric acid, sodium chloride, potassium chloride and magnesium chloride to provide a chloride ion concentration of about 9 to about grams per liter of chloride ion in said bath; about 50 to about 200 grams per liter of sulfuric acid; and the balance essentially water at ourrent densities of about to about 150 amperes per square foot; removing said article from said bath; rinsing said article; transferring said article to a nickel electroplating bath; and electrodepositing nickel on the anodically treated nickel surface of said article whereby an improved bonding of a nickel electrodeposit to said treated nickel surface of said article is obtained.

10. A method for obtaining improved bonding of nickel electrodeposit to an article having a nickel surface which comprises establishing an aqueous acid bath containing at least one member selected from the group consisting of hydrochloric acid, sodium chloride, potassium chloride and magnesium chloride to provide at least about 9 grams per liter and up to about 195 grams per liter of chloride ion in said bath, acid from the group consisting of sulfuric acid and hydrochloric acid to provide a total acid content of about 50 to about 200 grams per liter in said bath, a copper compound from the group consisting of copper sulfate and cupric chloride to provide a cupric ion concentration in said bath of about 0.5 to about 30 grams per liter and the balance consisting essentially of water; anodically treating said article having said nickel surface in said bath at current densities of about 5 to about 150 ainperes per square foot for about 2 to about 5 min utes to activate said nickel surface of said article; removing said article from said bath; rinsing said article to remove adhering bath solution from the activated nickel surface of said article; transferring said article to a nickel electroplating bath; and electrodepositing nickel on the activated nickel surface of said article whereby an improved bonding of a nickel electrodeposit to the activated nickel surface of said article is obtained.

1. A method for obtaining improved bonding of nickel electrodeposit to an article having a nickel surface which comprises establishing an aqueous acid bath containing at least one member selected from the group consisting of .hydrochloric acid, sodium chloride, potassium chloride and magnesium chloride to provide at least about 9 grams per liter and up to about 195 grams per liter of chloride ion in said bath, acid from the group consisting of sulfuric acid and hydrochloric acid to provide a total acid content of about 50 to about 200 grams per liter in said bath, a copper compound from the group consisting of copper sulfate and cupric chloride to provide a cupric ion concentration in said bath of about 2 to about 10 grams per liter and the balance consisting essentially of water; anodically treating said article having said nickel surface in said bath at current densities of about 5 to about 150 amperes per square foot for about 2 to about 5 minutes to activate'said nickel surface of said article; removing said article from said bath; rinsing said article to remove adhering bath solution from the activated nickel surface of said article; transferring said article to a nickel electroplating bath; and electrodepositing nickel on the activated nickel surface of said article whereby an improved bonding of a nickel electrodeposit to the activated nickel surface of said article is obtained.

12. A method for obtaining improved bonding of nickelelectrodeposit to an article having a nickel surface which comprises establishing an aqueous acid bath containing at least one member selected from the group consisting of hydrochloric acid, sodium chloride, potassium chloride and magnesium chloride to provide at least about 9 grams per liter and up to about 195 grams per liter of chloride ion in said bath, acid from the group consisting of sulfuric acid and hydrochloric acid to provide a total acid content of about 50 to about 200 grams per liter in said bath, a copper compound from the group consisting of copper sulfate and cupric chloride to provide a cupric ion concentration in said bath of about 0.5 to about 30 grams per liter and the balance consisting essentially of water; anodically treating said article having said nickel surface in said bath at current densities of about 5 to about amperes per square foot for about 2 to about 5 minutes to activate said nickel surface of said article; removing said article from said bath; immersing said article in a water bath whereby a passive film is prevented from being formed on the activated nickel surface of said article; transferring said article to a nickel electroplating bath; and electrodepositing nickel on the activated nickel surface of said article whereby an improved bonding of a nickel electrodeposit to the activated nickel surface of said article is obtained.

13. A method for obtaining improved bonding of nickel electrodeposit to an article having a nickel surface which comprises establishing an aqueous acid bath containing at least one member selected from the group consisting of hydrochloric acid, sodium chloride, potassium chloride and magnesium chloride to provide at least about 9 grams per liter and up to about grams per liter of chloride ion in said bath, acid from the group consisting of sulfuric acid and hydrochloric acid to provide a total acid content of about 50 to about 200 grams per liter in said bath, a cop-' per compound from the group consisting of copper sulfate and cupric chloride to provide a cupric ion concentration in said bath of about 0.5 to about 30 grams per liter and the balance consisting essentially of water; anodically treating said article having said nickel surface in said bath at current densities of about 5 to about 150 amperes per square foot for about 2 to about 5 minutes to activate said nickel surface of said article; interrupting the anodic treatment of said article, passing air through said bath to oxidize cuprous ions to cupric ions; removing said article from said bath; rinsing said article to remove adhering bath solution from the activated nickel surface of said article; transferring said article to a nickel electroplating bath; and electrodepositing nickel on the activated nickel surface of said article whereby an improved bonding of a nickel electrodeposit to the activated nickel surface of said article is obtained.

RALPH CRYSLER MoQUlRE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS OTHER REFERENCES Iron Age, Sept. 26, 1940, pages 19, 20. Iron Age, Oct. 3, 1940, pages 32, 33.