US2457059A - Method for bonding a nickel electrodeposit to a nickel surface - Google Patents

Description

iatenied Dec. 21, 1948 METHOD FOR BONDING A NICKEL ELEC- TRODEPOSIT TO A NICKEL SURFACE Ralph Crysler McQuire, Port Colborne,.0ntario, Canada, assignor to The International Nickel Company, Inc., New York, N. Y., a corporation of Delaware No Drawing. Application February 26, 1946, Se-

rial No. 650,389. In Canada December 3, 1945 10 Claims.

The present invention relates to the treatment of a nickel starting sheet or other nickel surface in order to obtain adherence thereto of a subsequent nickel electro-plating and to the product obtained by such treatments.

The art has recognized the broad problem of securing satisfactoryv adherence or bonding between a nickel surface and a nickel electroplating. Thus, 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 the addition of other compounds thereto. An important feature of the process in the 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. U. S. Patent No. 2,299,054 discloses the application of an electric current for activation of the nickel starting sheet. I amaware that other processes have been proposed and attempted for the cleansing and activation of other metal bases, for example, iron, prior to the electro-deposition 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-platlng. This will be readily recognized by reference to an article by Pinner, Soderberg and Baker in "Modern Efectroplating, 1942, page 237, in which the authors point out the difficulty in obtaining a good bond between a ductile nickel coating and a relatively thin. brittle coating deposited from a high sulfate nickel bath.

In my ccpending applications U. S. Serial Numbers 635,774 and 635,775, both filed December 18, 1945, and entitled Method for bonding a nickel electro-deposit to a nickel surface, I have disclosed processes for securing adequate bonding between a nickel surface and a nickel electroplating. These processes involve the use of electric current and anodic treatment of the nickel surface. Furthermore, in my aforementioned copending applications, agitation is not an essential feature of the processes disclosed therein.

I 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 together with the fact that I do not utilize electric current in carrying out my novel process.

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

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 periodic 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-deposltion 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 the immersion of a nickel surface in an aqueous acid chloride-bearing bath containing a significant concentration of cupric ions. After the immersion treatment, the nickel surface is immediately immersed in a rinse tank containing water and transferred to a nickel plating tank in which a nickel plating is deposited upon and securely bonded to the nickel surface. Those skilled in the art will realize that the expression nickel surface may refer to a nickel starting sheet, a prior' nickel plating, a cast or machined nickel surface, or a wrought nickel surface. I

In practicing my invention, it is important that copper be prevented from depositing upon the nickel surface during the immersion treatment. Thus, I continuously pass compressed air through the solution while the immersion process is being carried out. In this manner,

' the copper is maintained in the state of highest oxidation and prevented from depositing upon the nickel surface being treated. Hence. I secure economy of operation in that it is not necessary to continuously add copper salts to the solution except to replace drag-out losses.

The composition of the bath employed for the immersion treatment of the nickel surface has an important effect upon the character of the bond obtained between the nickel-surface and the subsequently applied nickel plating. Thus, the acid chloride-bearing bath employed by the present invention contains at least about 9.0 grams of chloride ion per liter as I have found that the presence of chloride ions in the bath has a marked effect on improving the bonding properties of the nickel surface treated therein. While a bath containing about 9.0 grams per liter of chloride ion has been found satisfactory: I prefer to employ a bath containing about 30 to 36 grams per liter of chloride ion, as with the increased chloride ion-- concentration of the bath, the time period required for satisfactory immersion treatment of the nickel surface is decreased. Thus, I have found that satisfactory results are not obtained when a bath substantially devoid of chloride ions and containing about 50 to 200 grams per liter of sulfuric acid is employed. However, by adding chloride ions to the sulfuric acid bath, such as by adding 15 to 60 grams per liter of sodium chloride, the bonding properties of a nickel surface treated therein are markedly improved. It will, of course, be understood that an equivalent quantity of chloride ion can be added by employing other suitable water soluble sources of chloride ions, such as potassium chloride, magnesium chloride, hydrochloric acid, etc. Furthermore, satisfactory results are also obtained by employing an acidic bath that does not contain sulfate ion. Thus, for example, a solution containing about 50 to 200 grams per liter of hydrochloric acid gives satisfactory results for treating a nickel surface to which a securely bonded nickel electrodeposit is subsequently applied.

. In accordance with the invention, about 0.5 to about 30 grams per liter of cupric ion in the form of any suitable water soluble source of copper ions is added to the acid bath employed, such as the baths hereinbefore described. However, the preferred range of cupric ion concentration is from about 2 to about 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 electrodeposit is to be obtained. In the absence -of cupric ion, the nickel surface remains relatively passive and the required activation of the surface is not obtained. Consequently, satisfactory adherence of a subsequent nickel plating to the surface is not obtained.

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

It is essential in carrying out the present invention to maintain the copper in the bath in the cupric state during the immersion treatment of the nickel surface. Hence, the bath is agitated by blowing compressed air therethrough during the immersion treatment whereby the copper is maintained in the state of highest oxidation. I have found that if such agitation is not employed, copper deposits upon the nickel surface. However, it is within the scope of my invention to desired results. Any further increase in chloride ion concentration of the bath does not substantially affect the time required for satisfactory treatment of the nickel surface.

Although a longer time period of treatment than hereinbefore described may be employed, I have found that a certain amount of nickel dissolves in the bath during the immersion treatment, and accordingly, the time of treatment should be kept as low as possible in order to decrease the amount of nickel dissolved. Entirely satisfactory results are obtained as long as the nickel surface is immersed in the novel coppercontaining bath of the present invention for about 5 to 10 minutes as hereinbefore described. The

advantages of activating the nickel surface in as short a period of time as possible will be read-- ily apparent to those skilled in the art as it decreases to a large extent the number of tanks which must be made available to carry out the treatment with resultant decrease in floor space and investment charges.

After the immersion treatment is completed. the nickel surface is removed from the bath andimmediately given a water rinse. After removal from the rinse tank, the treated nickel surface should be placed in a nickel plating tank within about 60 minutes after removal from the rinse tank and nickel plated thereon. Otherwise, if the treated article is allowed to stand in air for more prolonged periods following treatment, a passive film will form on the nickel surface. In the event it is not desired to apply the nickel plating shortly after the surface is treated, the nickel surface should be kept immersed in a bath which will prevent the formation of a passive film on the nickel surface. Thus, the nickel surface may be immersed in a bath of clean water until plating is to be begun: otherwise, satisfactory bonding of the treated nickel surface to the electrodeposit of nickel is not obtained due to formation of a passive film on the treated nickel surface.

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

Example I A nickel starting sheet was immersed in an acid bath containing about 100 grams per liter of sulfuric acid, about 50 grams per liter of sodium chloride and about 5 grams per liter of cupric ion in the form of copper sulfate. immersion was continued for about 5 minutes at a temperature of about 80 F., with agitation of the bath by passing compressed air therethrough. After the treatment was completed, the starting sheet was removed from the acid bath and im-- mersed in a water rinse tank. From the rinse tank, the starting sheet was transferred to a nickel plating tank and nickel plated thereon until a deposit about 0.25 inch thick was obtained The Example I! An iron article having a nickel plating thereon was treated in an acid bath containing about 60 grams per liter of hydrochloric acid and about grams per liter of cuprlc ion in the form of cupric chloride. The immersion was continued for about 5 minutes at a temperature of about 80F. with agitation of the bath by passing compressed air therethrough. After the treatment was completed, the article was removed from the acid bath and placed in a rinse tank. After the water rinse, the article was immersed in a conventional Watts type nickel plating solution and a second deposit oi nickel plated thereon. It was observed that the second nickel plating had substantially no tendency to strip or peel from the first nickel electro-plating, and entirely satisfactory bonding between the two nickel platings was obtained.

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 hydrochloric acid, sulfuric acid and chloride ion concentrations. Thus, for example, the preferred lower amount of hydrochloric acid concentration set forth for an all-chloride bath is about 50 grams per liter. As hereinbefore stated, satisfactory results are obtained by employing the present invention when a chloride ion concentration lower than that equivalent to 50 grams per liter of hydrochloric acid is employed, for ex ample, a bath containing at least about 9 grams per'liter of chloride ion. However, baths having a concentration higher than about 9 grams per liter of chloride ion are preferred, as the increased chlorlde ion concentration allows for satisfactory treatment of the nickel surface in a shorter time. Although an upper amount of 200 grams per liter of hydrochloric acid has hereinbefore been shown to give satisfactory results, this concentration of hydrochloric acid was chosen for economic reasons, as greater concentrations can be employed without departing from the spirit and scope of the invention. Similarly,

' the concentration of sulfuric acid in the chloridebearing treatment bath may be varied from the range of 50 to 200 grams per liter hereinbefore shown; the stated range of 50 to 200-grams per liter of sulfuric acid in a bath containing at least about 9.0 grams per liter of chloride ion having been found to provide satisfactory treatment of nickel surfaces to'which a nickel electro-plating is subsequently applied. 1

Although thepresent invention has been desheet for about 5 minutes without the application of electric current from an external source in an aqueous bath containing about 100 grams'per liter of sulfuric acid, about .50 grams per liter 'of sodium chloride and about 5 grams per'liter of copper in the form of copper sulfate and the balance essentially water, maintaining said copper in the cupric state by passing air through said bath, removing said nickel starting sheet from said aqueous bath, rinsing said starting sheet with water, immersing said starting sheet in a nickel electro-plating bath and eiectroscribed in conjunction with certain preferred em- ,bodiments, it is to be understood that modifications and variations may be resorted to with-.1

out departing from the spirit and scope of the invention as those skilled in the art will readily depositing nickel on said nickel starting sheet.

2. A method for obtaining improved bonding" of a nickel electro-deposit to a nickel surface which comprises immersing a metal article having a nickel plating thereon for about 5 minutes without the application of electric current from an external source in an aqueous bath containing about grams per lit :r of hydrochloric acid, about 5 grams per liter of copper as cupric chloride and the balance essentially water, maintaining said copper in the cupric state by passing air through said bath, removing said metal article from said aqueous bath,'rinsing said metal article with water, immersing said metal article in a nickel electro-plating bath and electro-depositing nickel on the nickel surface of said metal article.

3. A method for obtaining improved bonding of a nickel electro-deposit to a nickel surface which comprises immersing an article having a nickel surface for about 5 to is minutes without the application of electric current from an external source in an aqueous bath containing about 50 to 200 grams per liter of sulfuric acid, about l5 to about 60 grams per liter of sodium chloride, copper sulfate in an amount to provide about 0.5 to 30 grams per liter of copper as cupric ion and the balance essentially water, passing air through said bath during immersion of said article, removing said article from said bath, rinsing'said article, immersing said article in a nickel electro-plating bath and electro-depositing nickel on the nickel surface of said article.

4. A method for obtaining improved bonding of a nickel electro-deposit to a nickel surface which comprises immersing an article having a nickel surface for about 5 tom m nutes without the application of electric current from an external source in an aqueous bath containing about 50 to about 200 grams per liter of hydrochloric acid, about 0.5 to 30 grams per liter of copper as cupric chloride and the balance essentially water, passing air through said bath during immersion of said article, removing said article from said aqueous bath, rinsing said article, immersing said article in a nickel electro-plating bath and electro-depositing nickel on the nickel surface of said article. l

5. A method for obtaining improved bonding of a nickel electrodeposit to a nickel surface which the application of electric current from an external source in an'aqueous acid bath containing about 50 to about 200 grams per liter of sulfuric acid; a chloride compound from the'group consisting of hydrochloric acid, sodium chloride,- potassium chloride andmagnesium chloride to tially water; passing air through said bath during immersion of said article; removing said article from said bath; rinsing said article; immersing said article in a nickel electroplating bath and electrodepositing nickel on the nickel surface'of said article.

6. A methodfor obtaining improved bonding of a nickel electrodeposit to a nickel surface which comprises immersing an article having a nickel surface for about to about minutes without the application of electric current from an external source in an aqueous acid bath containing about 50 to about 200 grams per liter of sulfuric acid; a chloride compound from the group consisting of hydrochloric acid, sodium'chloride, po-

tassium chloride and magnesium chloride to provide a chloride ion concentration of about 9 to about 36 grams per liter; a water-soluble copper compound to provide a cupric ion concentration of about 0.5 to about 30 grams per liter and the balance essentially water; passing air through said bath, during immersion of said, article; removing said article from said bath; rinsing said article; immersing said article in a nickel electroplating bath and electrodepositing nickel on the nickel surface of said article.

'7. A method for obtaining improved bonding of a nickel electrodeposit to a nickel surface which comprises immersing an article having a nickel surface for about 5 to about 10 minutes without the application of electric current from an external source in an aqueous acid bath containing about 50 to about 200 grams per liter of sulfuric acid; a chloride compound from the group consisting of hydrochloric acid, sodium chloride, potassium chloride and magnesium chloride to pro vide a chloride ion concentration of about 9 to about 36 grams per liter; 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 and the balance essentially water; passing air through said bath during immersion of said article; removing said article from said bath; rinsing said article; immersing said article in a nickel electroplating bath and electrodepositing nickel on the nickel surface of said article.

8. A method for obtaining improved bonding of a nickel electrodeposit to an article having a nickel surface which comprises establishin an aqueous acid bath containing at least about 9 grams per liter of chloride ion provided by one member selected from the group consisting of hydrochloric acid in an amount up to about 200 gramsper liter, sodium chloride up to an amount correspondingto about 36 grams per liter of chloride ion, potassium chloride up to an amount corresponding to about 36 grams per liter of chloride ion and magnesium chloride up to an amount corresponding to about 36 grams per liter ofchloride ion; acid from the group consisting of sulfuric acid and hydrochloric'acid to provide a total acid content in said bath of about 50 to about 200 grams per liter; 2. 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;

immersing said article having said nickel surface in said bath for about 5 to about 10 minutes without the application of electric current from an external source to activate said nickel surface of said article; passing air through said bath during immersion of said article 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.

9. A method for obtaining improved bondingof a nickel electrodeposit to an article having a nickel surface which comprises establishing an aqueous acid bath containing at least about 9 grams per liter of chloride ion provided by one member selected from the group consisting of hydrochloric acid in an amount up to about 200 grams per liter, sodium chloride up to an amount correspending to about 36 grams per liter of chloride ion, potassium chloride up to an amount corresponding to about 36 grams per liter of chloride ion and magnesium chloride up to an amount corresponding to about 36 grams per liter of chloride ion; acid from the group consisting of sulfuric acid and hydrochloric acid to provide a total acid content in said bath of about to about 200 grams per liter; a copper compound fromthe 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; immersing said article having said nickel surface in said bath for about 5 to about 10 minutes without the application of electric current from an external source to activate said nickel 'surface of said article; passing air through said 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.

10. A method for obtaining improved bonding of a nickel electrodeposit to an article having a nickel surface which comprises establishing an aqueous acid bath containing at least about 9 grams per liter of chloride ion provided by one member selected from the group consisting of hydrochloric acid in an amount up to about 200 grams per liter, sodium chloride up to an amount corresponding to about 36 grams per liter of chloride ion, potassium chloride up to an amount corresponding to about 36 grams per liter of chloride ion and magnesium chloride up to an amount corresponding to about 36 grams per liter of chloride ion acid from the group consisting of sulfuric acid and hydrochloric acid to provide a total acid content in said bath of about 50 to about 200 grams per liter; 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; immersing said article having said nickel surface in said bath for about 5 to about 10 minutes without the application of electric current from an external source to activate said nickel surface of said article; passing air through said bath during immersion of said article to oxidize cuprous ions to cupric ions; remov-- ing said article from said bath; immersing said trodepositing nickel on the activated nickel sur- I face of said article whereby an improved bonding of a nickel electrodeposit to the activated nickel surface of said article is obtained.

RALPH CRYSLER. McQUIREL.

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

UNITED STATES PATENTS Number Name Date 765,371 Aylsworth July 19, 1904 1,373,837 Schulte Apr. 5, 1921 OTHER REFERENCES Iron Age, Sept. 26, 1940, pages 19, 20; Oct. 3, 1940, pages 32, 33.