US2737463A

US2737463A - Method of copperizing aluminum and aluminum alloys

Info

Publication number: US2737463A
Application number: US283246A
Authority: US
Inventors: Ledra M Lawton; Stuart T Ross
Original assignee: Motors Liquidation Co
Current assignee: Motors Liquidation Co
Priority date: 1952-04-19
Filing date: 1952-04-19
Publication date: 1956-03-06
Anticipated expiration: 1973-03-06

Description

United States Patent F METHOD OF COPPERIZIN G ALUMINUM AND ALUMINUM ALLOYS Ledra M. Lawton and 'StuartT. Ross, Lockport, N. Y., assignors to General Motors Corporation, Detroit, Mich., acorporation of Delaware No Drawing. Application April 19, 1952, 'Serial No. 283,246

-Claims. (Cl. 117-130) This invention has to do with the application of metal coatings "to metal :surfaces and is more particularly concerned with the application of a coating of copper to the surface of aluminum and aluminum alloys.

The usual methods for applying copper to aluminum and its alloys have not been entirely satisfactory. For example, the usual methods of electroplating are'not satisfactory for coating aluminum withcopper and satisfactory electroplatedcoatings can be produced only by means of special and rather expensive methods. It also has been proposed heretofore to coatv aluminum with copper by contacting the aluminum surface with fused cuprous chloride. However, 'thismethod has not proven entirely satisfactory in practice. It has also been desired to produce aluminum havingclean coatings of copper thereon, such that the coated metals can :be soldered'more readily by ordinary methods 'thancan aluminum surfaces.

'One object of the present invention is to produce a novel and highly satisfactory method for coating aluminum and its alloys with copper.

Another object is to treat aluminum and aluminum al- 'loy surfaces so that they can be more readily soldered of an article or base member of aluminum or an alu minum alloy composed preponderantly of aluminum may be coated With an adherent, substantially impervious clean copper coating by a process which includes first coating the article with a slurry consisting of cuprous chloride suspended in rosin which has been 'plasticized with a terphenyl .type compound. The terphenyl type compond and rosin function to keep .the cuprouschloride in suspension. Afterthe article has been coated with theslurry as just described, it is treatedto remove excess pl asticizer .to form a dry coating. After'this is accomplished the aluminum article with-zthe :dry coating .is heated to an elevated temperature for a short period of time sufiicient to .cause the copper tobe deposited on the aluminum surface in an adherent form.

In accordance with a preferred embodiment of the invention the slurry consists .of .twop'arts by weight of finely .divided .cuprous chloride and one part .by weight of a paste consisting of .finely powdered .rosin intimately mixed with :a terphenyl .type compound which :may be illustrated by .the .following .formula, CHsCeH4.'CsHs. Any one or more of the isomers of terphenyl, singly or in mixtures, may be used. Specific examples are 1,3- diphenyl benzene and 1,4-diphenyl benzene. The preferred composition of the paste consists of 15 parts by weight of finely pulverized rosin and parts by weight of terphenyl as a plasticizer for the rosin. The rosin may be melted and the terphenyl. added. The aluminum or aluminum alloy article to be coated with copper has 2,737,453 Patented Mar. 6, 1956 ice applied to the surface thereof at approximately room temperature .(abont Fli0 3R), a coating of 'the slurry prepared as just described. The coating then is dried as by nneans iQf iheating Ito vaporize and drive off excess plasticizer. About 3010 :60 seconds at a temperature of approximately 3 0.01 to 350" F. i'has proven satisfactory in mostinstances. The .articlewith the dried coating then is heated to a temperature :of 750 F. in an oxidizing atmosphere at atmospheric pressure for a short time thereby :producing :anadherent coating of copper on the article. time :of about .30 seconds -.or less is all that is necessary. .After the copper :coating is formed on the aluminumoraluminum alloy article the excess cuprous chloride and rosin andplasticizer, if any, is washed olf the copper-coated article. An aqueous solution of potassium sc'hloride 101' ammonium hydroxide has been found particularly "suitable :for ause in the washing operation.

While -.the ;-.foregoing;.-is';a specific example of a presentlyzpreferred mode :ofprocedure in accordance with the invention, considerable-variation :in the conditions may .be employed with success. :For example, the slurry of cuprous chloride and paste consisting of rosin and terphenyltypecompondzmay waryirom about five parts by weight of :cuprous chloride-andone :part by .weight of the paste of rosin and iterphenyl to one part by weight of cuprous chloride and tone part by weight of the paste. Also, demperaturest'higher :and lower than approximately :room temperature may be employed in the first step of coating the aluminumor aluminumalloy with the slurry consisting .of cuprouslclilon'de, pulverized rosin and the plasticizer. Temperatures above F. cause or tend to cause breaking .of 1hessuspension. Temperatures as low as!60 F. {oraevenrsomewhattlower than this may be employed :under :certain .conditions. The temperature employed in the :drying step is :for thepurpose of driving 'ofi LthCJCXCCSS -plasticizer :and may be varied as desired withxthis purpose in mind. The'ftemperature of heating in forming "the copperrcoating may .also vary considerably from 750 :Forexample, temperatures .up \to as high as 850" F. :may be employed as well as lower tempera- ':tures such as';650 F. :or even :as low as :600 F. under some conditions. Where the higher temperatures are employed it is unnecessary to .;use as long a time for the heating .as where flower' temperatures are used. For .example, as low as flotsecondsimay be used at a temperature-of 33b011t800 F. {For temperatures as 'low as 600 or.650 kit isgpreferred to employ longer times "for'the heating .step.

Whileweryssatisfactory results .have been obtained by carrying out the heating step in an oxidizing atmosphere it is also contemplatedthat itheiheat:treatment may be carriedsout'in neutral iorrreducing atmospheres.

:In addition 'to;simpl.y'=iforming a coating of copper on aluminum the heat treatment at :elevated temperature conditions also causes some difiusion of the copper into the aluminum so dhat theztreated article consists of alu- 'mi-num or an aluminumalloy ehaving'a diffused zone of copper-aluminum alloy and this is covered with a coatingof copper-andin=case'the:article has been produced in an oxidizing atmosphere a *thin outer layer of an oxide of copper.

A'fter'theexcess cuprous chloride 'androsin (and plas-' ticizer if any) hasgbeen removed as "by washing, the aluminum "having the copper coating thereon maybe soldered to other similarly coated articles or to other metals. Also the copper coated article may be readily electroplated or coated with another metal if desired.

Various changes and modifications of the specific embodiments of our invention described herein may be made by those skilled in the art without departing from the spirit and principles of the invention.

We claim:

1. A method of applying a copper coating to a base metal having a surface composed at least preponderantly of aluminum comprising coating said base with a slurry of cuprous chloride suspended in rosin plasticized with a terphenyl type compound, thereafter heating said base and slurry thereon for a time and at a temperature sufficient to volatize excess plasticizer and thereby dry the slurry on said base and then heating the base and dried coating at a higher temperature'than the drying temperature and for a time sufficient to form a copper coating on said base.

2. A method of applying a copper coating to a metal base composed at least preponderantly of aluminum comprising coating said base with a slurry of cuprous chloride suspended in rosin plasticized with a terphenyl type compound, said slurry being at a temperature within the approximate range of 60 to 90 F., thereafter heating said base having the coating of the slurry thereon to a temperature and for a time sufiicient to drive off excess plasticizer to form a dry coating and thereafter heating the base metal and the dried coating thereon at a temperature within the approximate range of 600 to 850 F. for a time suificient to form a copper coating on said base.

3. A method of applying a copper coating to a metal base composed at least preponderantly of aluminum comprising coating said base with a slurry of cuprous chloride suspended in rosin plasticized with a terphenyl type compound, said slurry being at a temperature within the approximate range of 60 to 90 F., thereafter heating said base having the coating of the slurry thereon to a temperature of about 300-350 F. for a time of about 3060 seconds to form a dry coating and thereafter heating the base metal and the dried coating thereon at a temperature within the approximate range of 600 to 850 F. for a time of about 10 to about 30 seconds.

4. A method of applying a copper coating to a base metal composed at least preponderantly of aluminum comprising coating said base with a slurry of cuprous chloride suspended in rosin plasticized with terphenyl (CeH5-CsH4CsH5), the proportion of cuprous chloride in said slurry ranging from about five parts by weight of cuprous chloride to about one partby weight of the plasticized rosin to one part by Weight of cuprous chloride and one part by weight of plasticized rosin, thereafter drying said coating by heating at a temperature on the order of 300 to 350 F. for about 30 to 60 seconds, thereafter heating the base metal and dried coating to a temperature within the approximate range of 600 F. to 850 F. for a period of not over about 30 seconds and thereafter removing any excess cuprous chloride and rosin.

5. A method of applying a copper coating to a base metal composed at least preponderantly of aluminum comprising coating said base with a slurry of cuprous chloride suspended in rosin plasticized with terphenyl (CsHsCsH4CsH5), the proportion of cuprous chloride in said slurry ranging from about five parts by weight of cuprous chloride to about one part by weight of the plasticized rosin to one part by weight of cuprous chloride and one part by weight of plasticized rosin, said slurry being at a temperature within the approximate range of 6090 F., thereafter drying said coating by heating at a temperature on the order of approximately 300 to approximately 350 F. for about 30 to-60 seconds, thereafter heating the base metal and dried coat- 4 ing to a temperature within the approximate range of 600 F. to 850 F. for a period of about 10 to 30 seconds and thereafter removing excess cuprous chloride and rosin.

6. A method of applying a copper coating to a base metal composed at least preponderantly of aluminum comprising coating said base with a slurry consisting of about two parts by weight of cuprous chloride and one part by weight of a mixture of finely divided rosin and terphenyl (CsHsCsH4CeH5), said rosin and terphenyl being present in the proportions of about 15 parts by weight of rosin and 85 parts by weight of terphenyl, said slurry being at a temperature within the approximate range of -90 F., then heating said base metal to a temperature of approximately 300 to 350 F. for a short period of time sufiicient to remove excess terphenyl and form a dry coating on said base, and then heating said base metal with the dried coating thereon to a temperature of approximately 750 F. for a time of approximately 10 to 30 seconds.

7. A method of applying a copper coating to a base metal composed at least preponderantly of aluminum comprising coating said base with a slurry consisting of about two parts by weight of cuprous chloride and one part by weight of a mixture of finely dividedrosin and terphenyl (CsH5-C6H4CaI-I5), said rosin and terphenyl being present in the proportions of about 15 parts by weight of rosin and 85 parts by weight of terphenyl type compound, said slurry being at approximately room temperature, then heating said base metal to a temperature of approximately 300 to 350 F. for about 30 to 60 seconds to remove excess terphenyl and form a dry coat ing on said base and then heating said base metal with the dried coating thereon to a temperature of approximately 750 F. in an oxidizing atmosphere at atmospheric pressure for a time of approximately 10 to 30 seconds.

8. A method of applying a copper coating to a base metal composed at least preponderantly of aluminum comprising coating said base with a slurry consisting of two parts by weight of finely divided cuprous chloride and one part by weight of a paste consisting of about 85 parts terphenyl (C6H5-C6I'I4-C6H5) and '15 parts by weight of rosin, said slurry being applied to the aluminum at a temperature of about F., thereafter heating the coating for about 30 seconds to a temperature of about 350 F. to remove excess terphenyl and form a dry coating on said base and thereafter heating the base metal with the dried coating theron in an oxidizing atmosphere at a temperature of about 750 F. at atmospheric pressure for a time of about 30 seconds.

9. A process as in claim 4 in which any excess cuprous chloride and rosin are removed by washing in an aqueous solution of the class consisting of potassium chloride and ammonium hydroxide.

10. A process as in claim 8 in which any excess cuprous chloride and rosin are removed by washing in an aqueous solution of the class consisting of potassium chloride and ammonium hydroxide.

References Cited in the file of this patent UNITED STATES PATENTS 675,584 Betts June 4, 1901 1,370,967 Hommel Mar. 8, 1921 2,331,356 Swenson Oct. 12, 1943 2,462,631 Gittings et al. Feb. 22, 1949 2,551,712 SOby May 8, 1951

Claims

1. A METHOD OF APPLYING A COPPER COATING TO A BASE METAL HAVING A SURFACE COMPOSED AT LEAST PREPONDERANTLY OF ALUMINUM COMPRISING COATING SAID BASE WITH A SLURRY OF CUPROUS CHLORIDE SUSPENDED IN ROSIN PLASTICIZED WITH A TERPHENYL TYPE COMPOUND, THEREAFTER HEATING SAID BASE AND SLURRY THEREON FOR A TIME AND AT A TEMPERATURE SUFFICIENT TO VOLATIZE EXCESS PLASTICIZER AND THEREBY DRY THE SLURRY ON SAID AND THEN HEATING THE BASE AND DRIED COATING AT A HIGHER TEMPERATURE THAN THE DRYING TEMPERATURE AND FOR A TIME SUFFICIENT TO FORM A COPPER COATING ON SAID BASE.