US2064301A

US2064301A - Method of producing a bronze finish on copper and copper alloys

Info

Publication number: US2064301A
Application number: US752476A
Authority: US
Inventors: Jr John R Freeman; Rollo L Hungerford
Original assignee: American Brass Co
Current assignee: American Brass Co
Priority date: 1934-11-10
Filing date: 1934-11-10
Publication date: 1936-12-15
Anticipated expiration: 1953-12-15

Description

Patented Dec. 15, 1936 METHOD OF PRODUCING A BRONZE FINISH ON COPPER AND COPPER ALLOYS John B. Freeman, Jr., Cheshire, and Rollo L. Hunger-ford, Waterbury, Conm, assignors to The American Brass Company, Waterbury, Conn., a corporation of Connecticut No Drawing. Application November 10, 1934,

This invention relates to copper and copper alloys, and has for an objectto provide an improved method of producing a bronze finish on copper or copper alloys so as to give articles 5 made of such materials a weathered bronze appearance in a short time.

We are aware of the patent to Laist el al No. 1,428,170 granted September 5, 1922 in which is disclosed a process for coloring metallic cop 10 per to secure a colored surface of various shades of green and blue, byimmersing the copper article in a solution of copper nitrate and copper chloride, and then washing and treating with various solutions to make the colored coating 15 more adherent and less soluble.

In our process, however, we do not wish a colored coating, but secure a rich weathered bronze surface appearance which is very attractive.

20 In carrying out our method the articles of copper or copper alloy are cleaned free from scale, grease, dirt, or any similar surface imperfection. We then immerse the article in a hot concentrated solution of copper nitrate,

25 or otherwise subject it to the action of such solution, for such a period of time as experience has shown to be desirable. This is ordinarily from about five minutes to a half hour, depending on the temperature of the solution and the 30 alloy used, ordinarily about 15 minutes with a solution temperature of 80 to 90 C. has proven very satisfactory. The specimen is now washed in hot water, preferably at a temperature of about 80 to 100 C., and the specimen is then i5 dried. The specimen now has upon its surface a roughly adhering green salt consisting of basic copper nitrate under which is a hard adherent surface film of a mixture of cuprous and cupric oxides which has a desirable weathered 40 bronze appearance.

We have found that this green loosely adhering layer of basic salt can be readily removed by a buffing operation which also gives to the underlying surface film of cupric and cuprous 45 oxides a fine bronze sheen. The bufling operation is preferably performed with a soft cloth This process produces a very beautiful weat h,

ered bronze appearance on copper and copper 50 alloys, and has been found to give a particularly desirable appearance on such copper alloys as the silicon bronzes of the so-called Everdur Serial No. 752,476

4 Claims. 148-6) type. such for example as those containing-from about .1 to 10% silicon and up to 4 or 5% manganese, and similar alloys. It is, however, not confined to such alloys, but is adapted for treating copper and copper alloys in general. 5

Having thus set forth the nature of our invention, what we claim is:

1. A method of producing a weathered bronze coating p5 finish on articles of copper and copperalloys which comprises immersing the article in a'hot concentrated solution. of predominantly copper nitrate to form on the metal a surface film of copper oxide under copper salts, washing in hot water to loosen the copper salts, drying, and then bufiing the surface in such manner as to remove the salts and impart to the oxide film a weathered bronze appearance.

2. A method of producing a weathered bronze coating or finish on articles of copper and copper alloys comprising subjecting the article to the actionof a hot concentrated solution of predominantly copper nitrate to form a surface film of copper oxide and adhering copper salts, washing the article in hot-'water to loosen the copper salts and then drying, and then bufilng the surface in such manner as to remove the salts and impart a bronze finish to the copper oxides.

3. In a method of producing a weathered bronze coating or finish on articles of copper and copper alloys, the steps which consist in subjecting the article to the action of a hot concentrated solution predominantly of copper nitrate to produce thereon a coating of a green salt overlying a surface film of copper oxides, washing in hot water to loosen the green salt and drying, and then buffing the surface in such manner as to remove the colored salts and impart a bronze finish to the oxides.

4. A method of producing a weathered bronze 40 coating or finish on articles of copper and copper alloys comprising, cleaning the article and subjecting it to a hot concentrated solution of' predominately copper nitrate for a sufiicient time to produce on its surface a roughly adhermg salt of basic copper nitrate over a surface film of copper oxides, then washing the article in hot -wate r. to loosen thesal-tanddrylng, and buffing the surface to remove the. salt and impart a bronze finish to the oxide film.

' JOHN R. JR.

ROLLO L. HUNGER-FORD.