US2903403A

US2903403A - Method of copper-plating metal surfaces

Info

Publication number: US2903403A
Application number: US458983A
Authority: US
Inventors: Strauss Wennemar
Original assignee: Dehydag Gmbh
Current assignee: Dehydag Deutsche Hydrierwerke GmbH
Priority date: 1954-02-10
Filing date: 1954-09-28
Publication date: 1959-09-08
Anticipated expiration: 1976-09-08
Also published as: US2956956A; BE535282A; FR1127418A; CH363211A; GB784091A; DE969855C; FR68296E; DE969005C; NL108797C; GB811773A; DE962489C

Description

United States Patent 56 METHOD OF COPPER-PLATING METAL SURFACES Wennemar Strauss, Dusseldorf Benrath, Germany, as-

signor to Dehydag, Deutsche Hydrierwerlie G.m.b.l-I., Dusseldorf, Germany, a corporation of Germany No Drawing. Application September 28, 1954 Serial No. 458,983

Claims priority, application- Germany February 20, 1954 9 Claims. (Cl; 204-32) This invention. relates to a method of copper-plating metal surfaces, and more particularly to a: method of copper-plating the surfaces of objects made of nonprecious metals.

The prior art discloses a great number of processes for depositing copper plates uponthe surfaces of metal objects. In general, these processes comprise first depositing a thin base coating of copper on the metal surface by immersing the object in a solution of a suitable copper salt containing a cyanide compound and finally depositing the desired ultimate copper plate upon the pre-treated surface either by the well-known dipping process or by electrolysis. The preliminary step of providing the metal surface with a base coating of copper prior toapplying the final copper plate is considered by the art to be indispensable to the production of good copper plates by electrolytic as well as other means. It is obvious, however, that this preliminary treatment renders the production of copper plated articles costly and that a method which will produce a high grade copper plate without such pro-treatment will make copper plated articles of all types readilyavailable to industry and the general public at a reduced cost and in quantities greater than heretofore.

It is therefore an object of the present invention to provide a method for copper-plating metal objects which does not require the deposition of a'thin base coating of copper prior to the deposition of the final copper plate on the surface of such objects.

Another object of this invention is to provide a method of depositing a copper plate upon the surface of objects made of non-precious metals whereby the final copper deposit can be applied directly to the clean metal surface of such objects.

Other objects and advantages will become apparent as the description of my invention proceeds.

I have found that objects made of non-precious metals such as iron, electrochemicallyactive steel, zinc, alumi num, and the like, can be copper-plated in an acid plating bath directly and without providing them with a preliminary'thin copper deposit by contacting such objects prior to the plating step, preferably immediately prior thereto, with an acid pickling bath which contains an inhibitor having a strong inhibiting effect.

The inhibiting effect of a compound suitable for use as an inhibitor in conjunction with the surface treatment of metal objects in acid pickling or plating baths can be defined as its capability of reducing the amount of hydrogen liberated by the attack of the acid bath upon the metal surface. Thus, the inhibiting elfect of an inhibitor for pickling and electroplating baths is to a certain degree equivalent to its corrosion-preventing effect and can be expressed in terms of the fractional amount of the maximum amount of hydrogen liberated by an acid bath which does not contain a corrosion-preventing additive. The largest amount of hydrogen liberated by the attack of an acid pickling or plating bath-when no inhibitor is added corresponds to a corrosion-preventing effect of By adding inhibitors to such baths the amount of hydrogen ice . 2* liberated due to the attack of the acid bath on the metal can be reduced to practically zero, which'corresponds'to an inhibiting or corrosion-preventing effect of Compounds used as inhibitors within the scope of my invention have an inhibiting effect ofat least 50%, which is termed a strong inhibiting effect.

While the theory of the action of inhibitors in acid pickling and plating baths is still unsettled, it is believed that inhibiting compounds are characterized in that they retard the electrochemical exchange on the metal surface and prevent the combination of the metal with oxygen, both by adsorption.

In the pickling bath the adsorptive action of inhibiting compounds added to the acid pickling bath results in minimizing the attack of the pickling solution on the virgin metal surface without appreciably retarding the rate of dissolution ofsurface scale, rust or dirt on the metal surface.

In the plating" bath the ads'or-ptive action of inhibitors and the retardation caused thereby result in a homogeni- Zation of the metal deposit which, in turn, produces metal deposits which are bright, adhere well to the metal surface, and are highly ductile.

In addition, it was found that suchinhibitors have a definite oxidation-retarding effect in the pickling bath.

Compounds which are suitable for use as inhibitors in the acid pickling bath and obviate the deposition of thin base coatings of copper on the metal objects prior to the application of the final copper plate thereon include organic acyclic or cyclic oxygen-, sulfuror nitrogen-containing compounds such as, for example, phenols, alcohols, aldehydes, ketones, sulfonic acids, sulfides, disulfides, sulfoxides or sulfones, aliphatic, cycloaliphatic, aromatic or heterocyclic bases, as Well as quaternary ammonium salts and other onium compounds, alkanolamines, especially triethanolamine andits salts, thiourea and its derivatives, and derivatives of guanidine and the like.

The adhering qualities of copper deposits applied to metal surfaces treated in pickling baths containing the above inhibitors can be further improved by adding to the pickling bath inorganic or organic reducing agents suchas, for example, bivalent tin chloride, sodium sulfite, sodium bisulfate, hydrazine sulfate and the like.

I have further found that the quality of final copper deposits applied directly to metal surfaces of objects made of non-precious metals, pre-treated in the above manner,

can be improved by adding to the plating bath certain brightening agents which not only enhance the brightness of the copper deposit, but also act as inhibitors by retarding the electrochemical exchange on the metal surface by adsorption. Examples. of brightening agents which have such dual characteristics are organic sulfonic acidsor their salts having the general structural formula aniline, lactic acid, as well as molasses, syrup, starch,

gelatine, glue and many others.

Finally, I have found that objects made of non preciousmetals can be copper-plated immediately, after pre-treat;

ment with a pickling bath and'without depositing a thin,

pre-coating of copper in a cyanide bath by using one and the same additive for the pickling bath and in the plating bath. The prerequisite, however, is that such an additive must act as an inhibitor with a strong inhibiting efiectin thepicklingbath and as a brightening agent and as an inhibitor with a strong inhibiting efiect in the plate bath. Examples of compounds which meet this requirement are the following sulf-onic acids, which contain a carbon atom bonded exclusively to a groupof hetero atoms:

Betaine salts of isothiourea-S-butane-w-sulfonic acid Betaine salts of N-phenyl-isothiourea-S-butane-w-sulfonic acid 2-mercaptobenzothiazole-S-propane-w-potassium sulfonate Thiocyanic acid-S-n-propylester-w-sodium sulfonate 2-thiobenzooxazole-Spropane-w-sodium sulfonate 2-thiometoxazine-s-butane-w-potassium sulfonate N,N-dimethyl-dithiocarbamic acid-n-propylester-w-sodium sulfonate N,N-pentamethylene-dithiocarbamic acid-n-propylester-wsodium sulfonate N-butyl-dithiocarbamic acid-n-butylester-w-sodium fonate N-p-tolyl-dithiocarbamic sulfonate Dithiocarbamic acid-n-propylene-w-potassium sulfonate S-phenyl-trithiocarbonic acid-n-propylester-w-sodium sulfonate Trithiocarbonic acid-bis-propylester-w-sodium sulfonate Isopropyl-xanthogenic acid-n-butylester-w-sodium sulfonate n-Butyl-xanthogcnic acid-n-propylester-w-sodium sulfonate Carbaminothiol acid-n-propylester-potassium sulfonate and the like.

In place of the sodium or potassium salts of the above compounds, the corresponding salts of other inorganic or organic basic elements or compounds can be used equally as effectively.

Within the scope of my invention, the final copper deposit may be applied directly to the pickled metal surface with the aid of the well-known dipping process or also by the usual electroplating process employing an electric current.

Aside from the addition of the above-described additives to the pickling bath and/or the plating bath in accordance with my invention, the methods usually ernployed in copper-plating metal objects need not be changed. For example, the basic pickling bath consists of the usual inorganic or organic acids or acid salts, particularly sulfuric acid, and the pickling and plating baths may also contain the usual wetting agents. The plating bath may also contain any of the well-known agents which promote the formation of smooth copper plates as well as other brightening agents and porosity reducing agents. The basic plating baths may consist of any of the well-known and usually employed copper salt solutions.

The method in accordance with my invention may be employed in copper-plating any non-precious metal such as iron, electrochemically active steel, zinc, aluminum, magnesium, and alloys thereof.

The following examples will enable persons skilled in the art to understand my invention more completely. However, it is understood that my invention is not limited to the particular examples cited below.

sul-

acid-n-propylester-w-potassium Example I Sheet iron was first pickled in a pickling bath consisting of a 2 N-sulfuric acid solution and containing 0.1% to 0.5% dibenzylsulfide as an inhibitor. Thereafter the pickled sheet iron was electroplated in a copper sulfate solution containing 0.5 -gm./liter dibenzylsulfoxide and 0.1 gm./liter thiourea, at room temperature and with a current density of 3 amps./dm. The copper deposit 4 produced thereby adhered well to the surface of the sheet 11011.

Example II Objects made of iron were pickled in a pickling bath of 2 n-sulfuric acid containing 0.1% to 0.5% dibenzylsulfoxide as an inhibitor. Subsequently the pickled metal objects were electroplated in a copper sulfate bath which contained 0.5 gm./liter N,N-dimethyl-dithiocarbamic acid-n-butylester-w-sodium sulfonate, at room temperature and with a current density of 4 amp./dm. The copper deposits produced thereby had excellent adhering properties.

Example Ill Objects made of sheet iron were pickled for 1 to 10 minutes in a pickling bath containing 1 gm./liter N,N- diethyl-dithiocarbamic acid-n-propylester-w-sodium sulfonate as an inhibitor. The pickled sheet iron objects were then copper plated at room temperature and with a current density of 5 amp./dm. in a copper sulfate solution which contained 1 gm./liter of N,N-diethyl-dithiocarbamic acid-n-propylester-w-sodium sulfonate as a brightening agent and inhibitor. The copper deposits produced thereby adhered very well to the metal surface and were bright and lustrous.

Example IV Sheet iron was pickled in a 2 N-sulfuric acid solution which also contained 1 gm./liter of the betaine salt of isothiourea-S-propane-w-sulfonic acid as an inhibitor. Subsequently the pickled sheet iron was immersed for 2 minutes in a copper sulfate solution which also contained 1 gm./liter of the above betaine salt as a brightening agent and inhibitor. A bright and well-adhering copper deposit was produced thereby on the surface of the sheet iron, which was sufiicient for a variety of uses and further treatment.

A few of these dip-plated sheets were then further copper-plated by electrolysis in a copper sulfate bath containing 1 gm./liter of the betaine salt of isothiourea-S- propane-w-sulfonic acid. The copper deposits obtained Objects made of sheet iron were pickled in a 2 N-sulfuric acid solution containing 5 gm./liter bivalent tin chloride and 1 gm./liter N,N-pentamethylene-dithiocarbamic acid-n-propylester-w-sodium sulfonate as an inhibitor. The pickled sheet iron objects were then dipped in a copper sulfate bath containing 1 gm./liter of N,N- pentamethylene dithiocarbamic acid-n-propylester-w-sodium sulfonate as a brightening agent and inhibitor. As in Example IV, the copper deposits produced thereby had excellent brightness properties and adhered to the metal surfaces even more completely than those obtained in Example IV. A few of these dip-plated objects were then electroplated in a copper sulfate bath as in Example IV. The copper deposits obtained were bright and lustrous and adhered very well to the surface of the objects.

While I have illustrated certain specific embodiments of my invention, I wish it to be understood that certain changes and variations may be made without departing from the spirit of my invention and the scope of the following claims.

I claim:

1. The method of producing copper deposits on surfaces of metal objects, said metal being selected from the group consisting of iron, zinc, aluminum and electrochemically active steels, which comprises pickling said objects in an acid pickling bath containing dibenzylsulfide as an inhibitor, and thereafter applying the final copper plate directly to the pickled objects on which a layer of inhibitor from said pickling bath solution remains adherent by electroplating said objects in an acid solution of copper sulfate, said solution containing small amounts of dibenzylsulfoxide and thiourea.

2. The method of producing copper deposits on surfaces of metal objects, said metal being selected from the group consisting of iron, zinc, aluminum and electrochemically active steels, which comprises pickling said objects in an acid pickling bath containing dibenzylsulfoxide as an inhibitor, and thereafter applying the final copper plate directly to the pickled objects on which a layer of inhibitor from said pickling bath solution remains adherent by electroplating said objects in an acid solution of copper sulfate, said solution containing small amounts of N,N-dimethyl-dithiocarbamic acid n-butylester-w-sodium sulfonate.

3. The method of producing copper deposits on surfaces of metal objects, said metal being selected from the group consisting of iron, zinc, aluminum and electrochemically active steels, which comprises pickling said objects in an acid pickling bath containing an inhibitor compound having an inhibiting effect of at least 50% and thereafter applying the final copper plate directly to the pickled surface of said objects to which a quantity of pickling bath solution remains adherent by electro plating said objects in an acid solution of a copper salt.

4. The method of producing copper deposits on surfaces of metal objects said metal being selected from the group consisting or iron, zinc, aluminum and electrochemically active steels, which comprises pickling said objects in an acid pickling bath containing an inhibitor having an inhibiting effect of at least 50% and thereafter applying the final copper plate directly to the pickled surface of said objects to which a quantity of pickling bath solution remains adherent by electroplating said objects in an acid solution of a copper salt, said solution containing a brightening agent.

5. The method of producing copper deposits on surfaces of metal objects, said metal being selected from the group consisting or iron, zinc, aluminum and electrochemically active steels, which comprises pickling said objects in an acid pickling bath containing an inhibitor having an inhibiting effect of at least 50% and thereafter applying the final copper plate directly to the pickled surface of said objects to which a quantity of pickling bath solution remains adherent, by electroplating said objects in an acid solution of a copper salt, said solution containing an inhibitor.

6. The method of producing copper deposits on surfaces of metal objects, said metal being selected from the group consisting or iron, zinc, aluminum and electrochemically active steels, which comprises pickling said objects in an acid pickling bath containing an inhibitor having an inhibiting effect of at least 50%, and thereafter applying the final copper plate directly to the pickled surface of said objects to which a quantity of pickling bath solution remains adherent by electroplating said objects in an acid solution of a copper salt, said solution containing a brightening agent and an inhibitor.

7. The method of producing copper deposits on surfaces of metal objects, said metal being selected from the group consisting or iron, zinc, aluminum and electrochemically active steels, which comprises pickling said objects in an acid pickling bath containing N,Ndiethyldithiocanbamic acid-n-propylester-w-sodium sulfonate, and thereafter applying the final copper plate directly to the pickled surface of said objects on which a layer of inhibitor from said pickling bath solution remains adherent by electroplating said objects in an acid solution of copper sulfate, said solution containing small amounts of N,N-diethyl-dithiocanbamic acid-n-propylester-w-sodiurn sulfonate.

8. The method of producing copper deposits on surfaces of objects, said metal being selected from the group consisting of iron, zinc, aluminum and electrochemically active steels which comprises pickling said objects in an acid pickling bath containing a small amount of the betaine salt of isothiourea-S-propane-w-sulfonic acid, and thereafter applying the final copper plate directly to the pickled objects on which a layer of inhibitor from said pickling bath solution remains adherent by contacting said objects with an acid solution of copper sulfate, said solution containing the betaine salt of isothiourea-S-propane-w-sulfonic acid.

9. The method of producing copper deposits on surfaces of metal objects, said metal being selected from the group consisting of iron, zinc, aluminum and electrochemically active steels, which comprises pickling said objects in an acid pickling bath containing bivalent tin chloride and N,N-pentamethylene-dithiocarbamic acidn-propylester-w-sodium sulfonate, and thereafter applying the final copper plate directly to the pickled objects on which a layer of inhibitor from said pickling bath solution remains adherent by contacting said objects with an acid solution of copper sulfate, said solution containing N,N-pentamethylene-dithiocarbamic acid-n-propyb ester-w-sodium sulfonate.

References Cited in the file of this patent UNITED STATES PATENTS 2,217,921 Saukaitis Oct. 15, 1940 2,363,973 Kennedy et al Nov. 28, 1944 2,366,737 Loder et al. Jan. 9, 1945 2,389,181 Brown Nov. 20, 1945 2,410,844 Signaigo et al. Nov. 12, 1946 2,424,887 Henricks July 29, 1947 2,511,988 Myers et al. June 20, 1950 2,560,979 Pessel July 17, 1951 2,563,229 Faust et al. Aug. 7, 1951 2,700,020 Pierce Jan. 18, 1955 2,742,412 Cransberg et al Apr. 17, 1956 FOREIGN PATENTS 602,591 Great Britain May 31, 1948 888,493 Germany July 8, 1949 637,453 Great Britain May 17, 1950 OTHER REFERENCES Metal Ind., Feb. 16, 1945, page 108,

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 2 ,903,403 September 8, 1959 Wennemar Strauss t' error appears in the -printed specification It is herebfi certified the quiring correction and that the said Letters of the above numbered patent re Patent should read as corrected below.

Column 3, line 7, for "plate" read plating line 16, for "thiobenzooxazole" read m thiobenzoxazole line 32, for "Butyl" read butyl column 5, lines 2'7 38, and 4% for er iron", each occurrence, read of iro.

th day of March 1960.,

and column (a, line l 9 an: a

Signed and sealed this 29 Attest: KARL Ho AXLINE ROBERT C. WATSON Commissioner of Patents Attesting Oificer

Claims

3. THE METHOD OF PRODUCING COPPER DEPOSITS ON SURFAES OF METAL OBJECTS, SAID METAL BEING SELECTED FROM THE GROUP CONSISTING OF IRON, ZINC, ALUMINUM AND ELECTROCHEMICALLY ACTIVE STEELS, WHICH COMPRISES PICKLING SAID OBJECTS IN AN ACID PICKLING BATH CONTAINING AN INHIBITOR COMPOUND HAVING AN INHIBITING EFFECT OF AT LEAST 50% AND THEREAFTER APPLYING THE FINAL COPPER PLATE DIRECTLY TO THE PICKLED SURFACE OF SAID OBJECTS TO WHICH A QUANTITY OF PICKLING BATH SOLUTION REMAINS ADHERENT BY ELECTROPLATING SAID OBJECTS IN AN ACID SOLUTION OF A COPPER SALT.