US2285549A - Process of electrodepositing an adherent layer of copper from copper refinery electrolyte on alloys of iron and/or nickel containing chromium - Google Patents

Description

Patented June PROCESS OF ELECTRODEPOSITING AN AD- HEBENT LAYER OF COPPER FROM COP- PER REFINEBY ELECTBOLYTE ON ALLOYS OF IRON AND/OR NICKEL CONTAINING GHBOMIUM Andrew Wesley, Plainfield, and Harry R. Copson, Westfield, N. 1., assignors to The International Nickel Company, Inc., New York, N. Y., a corporation of Delaware No Drawing. Application April 26, 1938,

Serial No. 204,304

6 Claims.

The present invention relates to a process of electrodepositing an' adherent coating of copper from copper refinery electrolyte on an alloy of iron and/or nickel which contains chromium, and, more particularly, to a process of coating alloys of the 80% nickel-14% chromium and stainless steel types, with an adherent layer of copper electrodeposited from a bath of copper refinery electrolyte.

For certain purposes, it is desirable to have a composite metal, one layer of which is copper and another layer of which contains chromium or is constituted of a nickel-chromium-iron alloy. Considerable difficulty has heretofore been experienced in securing good adherence between the surface of a chromium-containing article, especially an article made of a chromium-containing alloy of nickel and/or iron of the stainless type, and the surface of a copper layer when the latter was formed by electrodeposition. Without satisfactory adherence between the foundation metal and the electrodeposited layer it is not possible to work or fabricate the product, particularly to cold roll, draw or work the product without great losses due to the tendency, of the layers to pull apart in spots or to separate altogether.

The problem of electrodepositing an adherent layer of copper on products made of stainless alloys of the chromium-nickel, chromium-iron and chromium-nickel-iron types has inspired considerable research, but none of the processes developed, so far as we are aware, hasb een'ene tirely convenient, thoroughly reliable and wholly satisfactory and successful in practical, commercial and industrial application, especially with large articles or products.

We have discovered a process of electrodepositing an adherent copper coating from tank house or regular copper refinery electrolyte on chromium-containing alloys of the stainless type.

It is an object of the present invention to provide a process of electrodepositing an adherent coating of copper from a plating bath of tank house or regular copper refinery electrolyte on a body made of chromium-containing alloy, such as iron and/or nickel alloys of the stainless type.

It is another object of the invention to provide a process of obtaining an adherent coating of copper by electrodeposition from a plating bath of tank house or regular copper refinery electrolyte on a body made of a chromium-containing alloy, such as an alloy of the 80% nickel- 14% chromium-6% iron or stainless steel types,

which body has been pretreated to remove any oxygen-containing or other passive film from its surface and then covered with a protective film of metal, such as nickel, prior to the copper deposition.

It is a further object of the present invention to provide a process of electrodepositing a thick layer of copper from regular copper refinery electrolyte or tank house electrolyte on a body made from an alloy of the nickel-14% chromium-6% iron type or from stainless steel, which copper-layer adheres so tightly to the foundation metal that cold rolling and/or drawing do not destroy the bond between them.

It is within the contemplation of the present invention to providea process of electrodepositing an adherent coating of copper from a bath of regular copper refinery or tank house electrolyte on a body made from chromium-containing alloy of iron and/or nickel, which process is capable of being practiced on an industrial scale with conventional appliances and equipment, and which is relatively cheap and permits wide commercial and industrial use.

Other objects and advantages will become apparent from the following description.

Generally speaking, the present invention contemplates a process of obtaining an adherent coating of copper byv electrodeposition from a bath of tank house or regular copper refinery electrolyte upon a body made of a chromiumcontaining alloy, such as nickel-chromium alloy, stainless steel or the like, which process comprises the steps of removing a passive oxygen-containing or other film from the surface of the body to be coated; protecting the body against reformation of such. film by covering it with a film of protective metal, such as nickel, without removing the body from the situs of the first operation; electrodepositing upon the said film of protective metal a thin layer of copper from a relatively pure electrolyte; and then transferring the body to a plating bath of tank house or regular copper refinery electrolyte where a heavy layer of copper is deposited upon it.

The body of foundation metal to be coated is preferably freed from grease in any suitable manner, as those skilled in the art will readily understand, and then immersed in a solution containing hydrochloric acid and nickel chloride where the oxygen-containing or other passive film is removed. While the body is still immersed in the solution where the passive film is removed, a layer of nickel is electrodeposited on the active mation of a passive film when again exposed to air. The body is then transferred to a relatively pure copper plating bath. low in impurities, especially antimony, where a thin copper layer is electro-deposited over the nickel layer. The final deposit of copper is made in a plating bath of tank house or regular copper refinery electrolyte to which the copper and nickel coated body is next transferred and in which a relatively heavy layer is formed under usual plating conditions.

For the purpose of giving those skilled in the art a better understanding of the invention, the following illustrative example is given of a preferred procedure of carrying the invention into practice.

A body or article made of a nickel-chromiumiron alloy containing about 79% nickel, about 13% chromium and about 7% iron was pumice scrubbed until there was no water break. The degreasing and cleaning of the surface of the body or article may, of course, be accomplished by any other suitable method as those skilled in the art will understand.

The degreased and cleaned body or article was then immersed in an acid nickel chloride solution having the following composition:

Grams per liter NiCl2.6H2O, about 240 E01, about 36 The temperature of the solution was kept at about 70 F. It will be evident that the removal of the passive film could be accomplished in a solution containing no nickel chloride and that this salt could be added thereto in proper amount after the passive film had been removed.

The nickel-chromium-iron article or body was made anode to anodically treat the surface thereof for about 2 minutes at a current density of about amperes per square foot (2.2 amperes per square decimeter) using nickel electrodes as cathodes. While the article was maintained in the solution, the current was then reversed and nickel was electrodeposited on the anodically treated surface of the article for about 12 minutes at a current density of about 20 amperes per square foot (2.2 amperes per square decimeter).

The article now protected by nickel plate was removed from the solution and transferred without rinsing to an acid copper sulphate plating solution made from a good grade of sulphuric acid and copper sulphate low in impurities where a layer of copper about 0.001 inch thick was deposited under the following conditions:

Concentration of CuSO4.5HzO, about grams per liter 200 Concentration of H2804, about do 100 Temperature, about F 70 Current density, about amperes per square foot 33 Anodes, pure cathode copper.

2,285,549. alloy surface to protect the body against refor- The process of pretreating the foundation metal comprising immersing a cleaned article or body in a nickel chloride-hydrochloric acid bath and depositing on the active surface thereof a thin film of nickel prior to transferring the body to a copper plating bath, forms the subject matter of the copending application of Andrew Wesley, Serial No. 177,462, filed December 1, 1937. The satisfactory adherence of electrodeposited copper to an article made of a chromium containing alloy of the stainless type,-e. g., the nickel- 14% chromium or stainless steel types, appears to depend upon a number of critical conditons, one of which is the substantially complete absence of any oxygen-containing or other passive film on the surface of the article to be plated. While it is not diflicult to remove such a film in an acid bath as described hereinabove, it had been impracticable on an industrial scale to prevent reformation of such a film during transfer of the article to the copper plating bath from the film removing solution. The deposition of a film of protective nickel on the article while it was still in the acid bath in accordance with the process of the said copending application successfully prevented reformation of an oxygen-containing film on the article during the transfer to the copper plating bath, and a satisfactory bond between the foundation metal and the Copper layer was obtained as long as the copper platin bath was relatively pure. When copper refinery or tank house electrolyte was used, however, it was found that the copper layer did not adhere satisfactorily in all cases.

Experiments indicated that a cause of the failure to obtain good adherence between the nickel coated foundation metal and a copper layer deposited from tank house or regular copper refinery electrolyte was traceable to the presence of impurities in the electrolyte in amounts sufiicient to impair the bond between the copper layer and the nickel plated body. The impurities may be displaced from solution by action of the nickel film present on the foundation metal, resulting in the formation of a non-adherent layer of impurities, or of material containing impurities, on the nickel coated foundation metal. Such a film of impurities, or of material containing impurities, would prevent the adherence of the subsequently deposited copper layer to the nickel plated foundation metal. By depositing a thin layer of relatively pure copper on the nickel film as hereinbefore described, before the nickel plated body is placed in the bath of tank houseor copper refinery electrolyte, the formation of a nonadherent film of impurities, or of material containing impurities, on the nickel and copper plated body is effectively prevented when the body is transferred to tank house or regular copper refinery electrolyte. As a result, the bond between the copper layer and the foundation metal is very tenacious and resists separation of the layers when the article or body is subsequently cold rolled or drawn.

Tests made to determine the effect of antimony, as an example of an impurity commonly present in tank house or copper refinery electrolyte, upon the adhesion of electrodeposited copper to a nickel plated body of nickel-chro- 5 mium alloy appear to substantiate the explanation of the phenomenagiven in the preceding paragraph. In conducting these tests, the method employed to determine the adhesion of the copper to the nickel plated body was similar to that described by Mr. Ollard in Faraday Society Transaction, vol. 21,- 1925-26, pp. 81-90, and by Mr. Hothersall in Transactions of the Electrochemical Society, vol. 64, 1933, pp. 69-85. Briefly stated, test specimens of an alloy containing about 79% nickel, 13% chromium and 7% .iron were prepared in the form of rods 1" in diameter and about 1 long. After cleaning and removing the passive film as hereinbefore described, the test specimens were coated with a thin protective layer of nickel while still immersed in the hydrochloric acid-nickel chloride bath. Test specimens were then transferred to various copper plating baths having regulated amounts of antimony dissolved therein and a heavy deposit of copper was plated on an end of each rod. The deposit was somewhat disc shaped and about 1 in diameter and 0.1' thick. When removed from the copper plating bath, the deposit encircled a portion of the rod and in order to obtain a true value of the surface adhesion, the specimens were placed in a lathe where the deposit was machined off the cylindrical face of the rod to leave a disc shaped deposit adhering to the rod at the end only. A hole was then bored through the deposit into the end of the rod, thereby leaving a ring of copper adhering to the rod by an annulus exactly across. The adhesion was determined by measuring the load required to detach the copper ring from the rod. A more complete description of the test, accompanied by drawings, is contained in the above cited publications and need not be repeated here as those skilled in the art are familiar with the test. Typical results are set forth in Schedule I.

Rod No. 5 was prepared in the same manner as Rod No. 4 except that a layer of chemically pure copper 0.001 thick was deposited on the nickel plated rod before it was placed in the bath con-- taining 0.6 gram per liter of antimony. When this specimen was placed in the testing machine,

taining iron and/or nickel alloy is not a simple oxide; or that impurities in copper refinery or tank house electrolyte other than antimony may contribute to the formation of a non-adhering film on the nickel plated article when it is placed therein, or otherwise prevent the direct deposition of a satisfactory adherent heavy layer of copper from such electrolyte upon the nickel plated body. The present invention provides a process whereby-it is possible to obtain a satisfactory and commercially acceptable adherent copper deposit from tank house or copper refinery electrolyte on a body or article made of a chromium-containing alloy of iron and/or nickel, with standard equipment and on an industrial scale.

house electrolyte containing antimony in amounts the copper failed at a load of 11,800 pounds per square inch without breaking the bond between the copper and the foundation metal. This phenomenal increase from about 80 pounds per square inch on the one hand to more than 12,000 pounds per square inch on the other demonstrates the value and importance of the present invention in assuring strong adhesion between the chromium-containing foundation metal and the copper deposited from tank house and copper refinery electrolyte which often contains detrimental amounts of impurities including antimony.

The copper plating bath in which the nickel plated body of chromium-containing stainless alloy is given the preliminary thin copper coating should be low in impurities. Under no circumstances should it contain over 0.3 gram of antimony per liter and preferably it should contain less than 0.1 gram per liter.

While the foregoing theory is believed to be correct, it is to be distinctly understood that the invention is not dependent upon any particular theory of operation. Thus, it may be that the greater than about 0.1 gram per liter to produce a composite body capable of being worked including cold rolling and drawing which comprises anodically activating a degreased body of nickelchromium alloy at about 20 amperes per square foot for about 2 minutes in an aqueous electrolyte containing about 36 grams of hydrochloric acid per liter and about 240 grams of nickel chloride per liter and in the presence of pure nickel electrodes to obtain a body of nickel-chromium alloy having an active surface, reversing the polarity of said body and electrodepositing a film of nickel on said active surface from said aqueous electrolyte during a period of about 2 minutes at a current density of about 20 amperes per square foot to obtain a body of nickel-chromium alloy having a protected surface, without rinsing, transferring said body having a protected surface to a first aqueous copper electrolyte containing about 200 grams of copper sulphate per liter, about grams of sulfuric acid per liter and being substantially devoid of antimony in amounts sufilcient to reduce the breaking load of the bond between the body of nickel-chromium alloy and the copper electrodeposited thereupon below about 9000 pounds per square inch, electrodepositing a film of copper about 0.001 inch thick thereon to obtain a protected body of nickel-chromium alloy having a film of copper thereon, anodically treating the copper surface of said protected body for about 3 minutes at a current density of about 13 amperes per square foot in an aqueous impure copper plating electrolyte comprising copper'refinery tankhouse electrolyte, reversing the polarity of said protected body and electrodepositing a relatively thick layer of copper from said impure copper electrolyte comprising copper refinery tankhouse electrolyte containing antimony in amounts greater than about 0.1 gram per liter to produce a composite body comprising a base of nickel-chromium alloy, a protective film of nickel, a film of copper, and a relatively thick layer of copper, the bond between said body of nickel-chromium alloy and said thick layer of copper being capable of withstanding a breaking load of at least 9000 pounds per square inch, and cold working said composite body to produce a worked body without rupture of the aforesaid bond.

2. A process for utilizing copper refinery tank house electrolyte containing antimony in amounts greater than about 0.1 gram per liter to produce a composite body capable of being worked including cold rolling and drawing which comprises anodically activating a degreased body passive film that forms on the chromium-conof. nickel-chromium alloy at about 20 amperes per square foot for about 2 minutes in an aqueous Y electrolyte containing about 36 grams of hydrochloric acid per liter and about 240 grams of nickel chloride per liter to obtain a body of nickel-chromium alloy having an active surface, reversing the polarity of said anodically activated body and electrodepositing a film of nickel on said active surface from said aqueous electrolyte, said film of nickel being at least that amount deposited by passing a current of 20 amperes per square foot for six minutes to provide a body of nickel-chromium alloy having a protected surface, electrodepositing a film of copper at least about 0.001 inch thick from a first aqueous copper electrolyte containing about 200 grams of copper sulphate per liter, about 100 grams of sulfuric acid per liter and being substantially devoid of antimony in amounts sufilcient to reduce the breaking load of the bond between the body of nickel-chromium alloy and the copper electrodeposited therefrom below about 9000 pounds per square inch to obtain a protected body of nickelchromium alloy having a thin film of copper, electrodepositing a relatively thick layer of copper from an impure copper electrolyte comprising copper refinery tankhouse electrolyte containing antimony in amounts greater than about 0.1 gramper liter to obtain a composite body comprising a base of nickel-chromium alloy, a protectivefilm of nickel, a film of copper and a relatively thick layer of copper, the bond between said Tbody of nickel-chromium alloy and said copper being capable of withstanding a breaking load of at least 9000 pounds per square inch, cold rolling said composite body, and deep drawing said cold rolled composite body to produce a rolled,.drawn body without rupture of the aforesaid bond.

3. A process for utilizing copper refinery tankhouse electrolyte containing antimony in amounts greater than about 0.1 gram per liter in the production of a,composi'te body capable of being. worked including cold rolling and drawing which comprises anodically activating a degreased body of nickel-chromium alloy at a current density of about 20 amperes per square foot in'an aqueous electrolyte containing about 36 grams of hydrochloric acid per liter to obtain a nickel-chromium body having an active surface capable of receiving an adherent electrodeposited film of nickel, electrodepositing a film of nickel on said nickel-chromium body while immersed in said aqueous electrolyte and in the presence of about 240 grams of nickel chloride per liter, said film of nickel being of sufficient thickness to provide a protected nickel-chromium body, i electrodepositing a film of copper about 0.001 inch thick from a first aqueous copper electroplating electrolyte substantially devoid of antimony to produce a protected nickel-chromium alloy body having a film of nickel thereon and a superimposed film of copper, and electrodepositing a thick layer of copper on said protected nickel-chromium alloy body from a second aqueous impure copper electroplating electrolyte comprising copper refinery tankhouse electrolyte containing antimony in excess of 0.1 gram per liter to obtain a composite body comprising a base of nickel-chromium alloy, a protective film of electrodeposited nickel, a film of electrodeposited copper, and a thick layer of electrodeposited copper, the bond between said thick layer of copper and said base being capable of withstanding a breaking load in excess of about 9000 pounds per square inch and being capable of withstanding the stresses of cold working including cold rolling and drawing without rupture of the aforesaid bond.

4. The process set forth in claim 3 wherein the first aqueous copper electroplating electrolyte substantially devoid of antimony is maintained at a temperature of about F.

5. The process set forth in claim 3 wherein the first aqueous copper electroplating electrolyte substantially devoid of antimony contains not more than about 0.1 gram of antimony per liter.

6. The process set forth in claim 3 wherein the both! of nickel-chromium alloy is selected from the group consisting of stainless steel and a nickel-chromium-iron alloy consisting of about nickel, 14% chromium an 6% iron.

- ANDREW WESLEY.

HARRY R. COPSON.