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Publication numberUS2364993 A
Publication typeGrant
Publication dateDec 12, 1944
Filing dateDec 29, 1942
Priority dateDec 29, 1942
Publication numberUS 2364993 A, US 2364993A, US-A-2364993, US2364993 A, US2364993A
InventorsWalter R Meyer
Original AssigneeWalter R Meyer
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Process for blackening copper or copper alloy surfaces
US 2364993 A
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Description  (OCR text may contain errors)

, one to eight hours.


Patented Dec. 12, a


' No Drawing. Application December 29, 1942, Serial No. 470,510

, 3 Claims.

The present invention relates to a process and composition for blackening'copper and copper alloys.

Heretoiore, copper and copper alloy surfaces have been blackened by the so-called oxidizing process in which the surface is cleaned and a copper sulphide film is formed by immersing the surface in solutions of sodium sulphide or ammonium sulphide or other water soluble sulphides. This produced brown or black coatings on the sur-' face. These sulphide films are not stable to oxidation, particularly when exposed to outdoor atmospheres, and have to be protected by subse-* quent treatments, such as lacquering or waxing, to provide aprotective coating thereover which must be renewed from time to time.

The surface is washed and then immersed in the dip of the present invention so as to provide the blackened coating.

One of the requirements of the solution for blackening a copper or copper alloy siu'face is that a minimum pH must be exceeded. This min- Another process involves the use of copper salt, v

such as copper sulphate, copper carbonate, or basic copper carbonate with ammonia in a bath. This process is used for applying blue black to hi-ass (copper zinc alloys) in the range of 65-35 to 80-20 copper zinc ratios by weight. In proper operation of this process, when copper carbonate is employed, for example, an excess of copper carbonate is required. Alloys containing higher copper contents than 80%, particularly the pure copper, are not blackened by this process to a deep black, but are colored a grayish black.

Still another method of blackening'copper and copper alloys involves the used sodium, 'potassium or ammonium persulphates, together with an alkali, such as sodium hydroxide or potassium hydroxide. This method, however, is very unsat isfactory because the persulphates are unstable and the life of the solution is relatively short, i. e.,

The present invention overcomes the diflicul ties of the prior process by providing a process and solution for direct oxidation of copper and copper alloy surfaces at low temperatures, less than 250 F., which process does not evolve irritating or harmful fumes, and the solution em-- ployed being stable over a period of days and This is accomplished by providing immersion of the surfaces in a hot aqueous bath of the coloring solution composed of sodium chlorite or potassium chlorite and either sodium hydroxide or potassium hydroxide.

In order to provide a uniform blackened surface by the process of the present invention, the surface may be cleaned and prepared by subjecting it to well known sulphuric acid-nitric acid bright dips, various concentrations of nitric acid and water, or etches containing chromic acid, chromates or dichromates with sulphuric acid.

coatings can be obtained in aqueous solutions having concentrations ranging between the following limits: sodium chl0rlte-5 g./l., sodium hydroxide-40 g./l. to sodium chlorite-saturated solution, sodium hydroxide-1000 g./l. The lower range of concentration requires approximately thirty minutes to blacken copper surfaces with the solution. operating at boiling point, whereas copper surfaces blacken in solutions of the high limits in approximately one minute when operated at boiling point.

These examples are given for copper surfaces. Usually somewhat higher temperatures and concentrations are employed for blackening copper alloys.

It has beeniound that coatings producedin solutions containing high concentrations of sodium hydroxide (above 200 g./l.) have a tan smut covering the black film underneath it. This smut can be easily wiped off exposing the black surfaces.

In normal commercial operation, however, the concentrations are maintained sumciently low so that'the smut does not appear. One proportion which has been very successful commercially includes one part by weight sodium chlorite to two parts by weight of sodium hydroxide, and this used at the rate of one to two pounds per gallon of water to form the bath which is most efficiently operated at from 200 F. to the boiling point of the solution.

In carrying out the process, the temperature required for the operation varies with the concentration of the component chemicals, the high concentrations permitting lower temperatures to be used. For example, with a concentration of sodium hydroxide of 10 g./l. and sodium chlorite at 10 g./l. a black color was obtained upon a copper surface at 175 F. in eighteen minutes, whereas with a concentration-of sodium hydroxide g./l. and sodium chlorite 150 g./l. a black was obtained upon a copper surface in fifteen minutes at 125 F.

By increasing the temperatures, the time required to produce the black surface may be effectively shortened. For example, the concentration of sodium hydroxide g./l. and sodium chlorite 10 g./l. can produce a black surface on copper in ten minutes if the temperature is raised to a boiling point of 216 F., and with the concentration of sodium hydroxide 150 g./l., sodium chlorite 150 g./l., black can be obtained in thirty seconds if the temperature of the bath is raised to the boiling point of the solution, namely. 250 F.

The black surfaces produced by the process are cupric oxide. These deep black surfaces are highly desirable in the manufacture of optical equipment, instruments, buttons and many other similar articles. Th appearances of these surfaces may be enhanced to present a greater depth of color by oiling, waxing or lacquering them.

The present invention is not limited to coating articles of solid copper or copper alloys, but may be used to coat surfaces of other metals which have been plated with copper or copper alloys when the coating thickness is greater than 0.00005" and the copper content of thealloy is greater than 60%.

It has been found that alkalies having lower pH in solution than sodium or potassium hydroxides, such as borax, trisodium phosphate, sodium metasilicate and sodium carbonate, are

ineffective for the present purpose when usedwith sodium chlorite. Also, it has been found that other oxidizing agents, such as potassium permanganate, sodium chlorate, sodium nitrate and sodium nitrite when mixed with caustic soda have proven ineffective to produce the black surface.

Variations and modifications may be made within the scope of this invention and portions of the improvements may be used without others.

I claim:

1. The process of producing a black surface on copper or copper alloy articles which comprises immersing the surface in a hot aqueous solution consisting essentially of an alkali selected from the group consisting of sodium hydroxide and potassium hydroxide and a chlorite selected from the group consisting of sodium chlorit and potassium chlorite.

2. The process of producing a black surface on copper or copper alloy surfaces which comprises immersing the surface in a hot aqueous solution of sodium chlorite and of an alkali selected from the group consisting of sodium hydroxide and potassium hydroxide, the concentration of the sodium hydroxide or potassium hydroxide and sodium chlorite being between about sodium chlorite-5 g./l., sodium hydroxide or potassium hydroxide-10 g./l. to sodium chlorite-saturated solution, sodium hydroxide or potassium hydroxide1000 g./l.

3. The process of producing a black surface on copper or copper alloy articles, which comprises immersin the surface in a hot aqueous solution of sodium hydroxid and sodium chlorite having a concentration between about sodium chlorite-5 g./l., sodium hydroxide-l0 g./l. to sodium chlorite-saturated solution, sodium hy- CIIOXidB-IOOO g./l.


Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US2437441 *Feb 14, 1945Mar 9, 1948Associated Chemical CompanyColoring metal surfaces
US2457480 *Apr 19, 1945Dec 28, 1948Lewis Earle BBlackening copper alloys
US2460896 *Aug 19, 1944Feb 8, 1949EnthoneComposition for blackening copper and copper alloy surfaces
US2460897 *Sep 14, 1944Feb 8, 1949EnthoneRendering aluminum and aluminum alloy surfaces corrosion resistant
US2460898 *Nov 4, 1944Feb 8, 1949EnthoneProcess and composition for coloring copper and copper alloy surfaces
US2475981 *Aug 1, 1946Jul 12, 1949Heatbath CorpProcess for blackening copper and copper alloys
US2481854 *Feb 14, 1946Sep 13, 1949EnthoneComposition to blacken surfaces of copper and of alloys containing copper
US2573320 *Mar 18, 1949Oct 30, 1951Pyrene Mfg CoFire extinguisher
US2745898 *Sep 20, 1952May 15, 1956Gen ElectricInsulated electric conductors
US2884161 *Sep 25, 1952Apr 28, 1959Gen ElectricComposite articles of metal and elastomer and method of fabrication
US2963538 *Apr 11, 1957Dec 6, 1960Sanders Associates IncFlat cables
US3107197 *Jun 5, 1957Oct 15, 1963Int Resistance CoMethod of bonding a metal to a plastic and the article produced thereby
US3150016 *Dec 27, 1960Sep 22, 1964Gen Motors CorpAntifriction bearing
US3389061 *Sep 5, 1967Jun 18, 1968Ass Ouvriers Instr PrecisionAnodization of a copper-nickelmanganese alloy
US4409037 *Apr 5, 1982Oct 11, 1983Macdermid IncorporatedAdhesion promoter for printed circuits
US4702793 *Jun 2, 1986Oct 27, 1987Etd Technology Inc.Rapid formation of uniform metal oxide layer
US4824511 *Oct 19, 1987Apr 25, 1989E. I. Du Pont De Nemours And CompanyMultilayer circuit board with fluoropolymer interlayers
US5106454 *Nov 1, 1990Apr 21, 1992Shipley Company Inc.Process for multilayer printed circuit board manufacture
US5250363 *Oct 26, 1992Oct 5, 1993Olin CorporationChromium-zinc anti-tarnish coating for copper foil having a dark color
US5288377 *Jan 19, 1993Feb 22, 1994Macdermid, IncorporatedCopper surface passivated with phosphate or copper oxide coating upon which resin is deposited
US5492595 *Apr 11, 1994Feb 20, 1996Electrochemicals, Inc.Reducing oxide whiskers on surface with acidic reducing solution containing thiosulfate, rinsing; good adhesion to resin
US5861076 *Sep 6, 1995Jan 19, 1999Park Electrochemical CorporationMethod for making multi-layer circuit boards
US5976228 *Sep 15, 1997Nov 2, 1999The Dexter CorporationSolution of an alkali metal borohydride and a quaternary ammonium ion; enhances corrosion resistance of copper oxide in printed circuits
US6506314Jul 27, 2000Jan 14, 2003Atotech Deutschland GmbhAdhesion of polymeric materials to metal surfaces
US8308893Feb 1, 2010Nov 13, 2012Ming De WangNano-oxide process for bonding copper/copper alloy and resin
U.S. Classification148/269
International ClassificationC23C22/63, H05K3/38
Cooperative ClassificationH05K3/385, H05K2203/0315, C23C22/63, H05K2201/0355
European ClassificationH05K3/38C6, C23C22/63