US1023291A - Coloring metals. - Google Patents

Description

UNITE STATES SALOMON AXELROD, OF OBERSCI'IONEWEIDE, GERMANY, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

QOLORING- METALS. I

No Drawing.

Specification of Letters latent.

Patented Apr. 16, mic.

Application filed December 16, 1908. Serial No. 467,802.

. When aluminium oxid is heated with oobalt salts, there is obtained a dark blue mass of cobalt ultra-marine or Thenards blue. Zinc. oxid, in the same manner, results in the so-called Rinmans green. Tin oxid is colored blue-green and magnesium oxid flesh-color. I find that if this reaction is carried out on a clean metallic surface of .the above metals, the same colors are. ob-

assumes a black color. The black coating thus produced adheres firmly to the metal and protects it from corrosion.

According to my present knowledge, the reactions here taking place are as follows: The originally formed combination of the metallic oxid and the cobalt salt, which, in all probability, consists of a double salt of the specific metal with the cobalt salt, unites with an excess of cobalt salt, and using for example, cobaltous nitrate, the resulting compound has a steel gray color, often with a metallic luster, and it probably has been transformed into a se'squioxid .of cobalt. This in turn is transformed by a stronger heating to the cobaltous-cobalicaoxid. ,In this manner, it is possible to produce brown, steel-gray, and surface ofthe specific metal by varying the heating temperature and; the excess of cobaltsalt. s

The manner of carrying out the foregoing procedure is as follows: The object to I be treated, either with previouswarming or while cold, is dipped into a neutral or alkaline solution of cobalt salt, such as cobaltous nitrate, and is subsequently gently, or more strongly heated according to the shade deblack colorations upon the;

sired. If desired, the solution also may be painted on with a soft brush- The degree of temperature andthe number of immersions are determined entirely by the shade desired. I 2

It is true that processes are known for producing a brown color upon aluminium, as byv heating the metal after it has been provided with a coating, of fresh white-ofegg', but the coating produced in this manner can be removed by energetic rubbing. According to the different procedure described by Dr. Getting, a brown color is produced upon aluminium by etching the metal, whereby the silicon and iron in the-commercial aluminium are brought out and pro-'- duce a surface coloration. This ives the aluminium not a black, but a brownlsh color.

The progress caused by the present invention lies chiefly in the fact that the metal is given a surface, not consist-ing of some superficial carbonaceous material, but a permaneiit dead-black metallic coating firmly adherent to the surface.

The present process also can be carried out relatively more cheaply and rapidly than processes used heretofore.

Although I have, described my invention with reference more particularly to aluminium, I desire it to be understood that other metals such as zinc, tin, magnesium, and their alloys, and in fact any metals forming colored compounds with cobalt salts may be treated in a similar manner, in order toproduce the above-described surface colorations.

I also mean by the appended claims to include the treatment of aluminium or other metal surfaces which have a surface film of oxid.

What I claim as new and desire to secure by Letters Patent of the United States, is,-

1. The process of producing a coating upon metals which consists i'nproviding the metals with a surface coating of cobalt salt and subsequently heating the metals moreor less strongly according to the shade de- 3. The process of surface-coloring metals P which consists in applying upon the metals a neutral solution of cobalt salts and heating the same more or less strongly acc0rding. to the shade desired.

4. The process-0f surface-coloring metal which consists in applying upon the surface of a metal, a coating of a cobalt compound and then heating the metal more or less strongly according to the shade of color desired. 4

5. An aluminium article having a surface coating, chemically combined therewith, of an adherent cobalt compound.

6. A metallic article having a cobalt compound chemically combined with its surface.

7. A metallic article having a black 00- 15 I balt compound chemically combined with its surface.

8. An aluminium article having on its surface, chemically combined therewith, a black adherent compound of aluminium and 20 cobalt.

In witness whereof, I have hereunto set my hand this 24th day of November, 1908.

SALOMON AXELROD.

WVitnesses: HARL BREKELEEN, ALFRED WOLF.