US1600076A - Electrodeposition of metallic chromium - Google Patents

Description

Patented Sept. 14, 1926.

UNITED'ZASTATES EIJ'I SUZUKI, OF TOKYO, JAPAN, ASSIGNOR -TO GENERAL ELEC'IBIO GOMPANYQA PATENT OFFICE.

CORPORATION OF NEW YORK.

EILECTRODEPOSITION on unranmc cnnoMIuM.

m} Drawing. Application 1118a July 31, 1925, Serial No. 47,370, and in Japan January 19, 1925.

This invention relates to improvements in the. electro-deposition of metallic chromium. Its primary object is to provide a process by means of which metallic chromium may be deposited. electrolytically upon metal surfaces in a more economical manner than heretofore.

A further object of the invention is to produce a chromium deposit which shall be more'adherent, dense, and resistant to high temperatures than the coatings hitherto produced.

One of the disadvantages of present chromium plating baths consists in the necessity of using metallic chromium itself as the anode. In view of the ditficulty of obtain- .ing chromium sheets or plates in a state of sufiicient purity for use as anodes in such baths, it is necessary to use platinum in lieu thereof, which, of course, entails considerable operating expense and great initial investment. Furthermore, even when chromium anodes are used, the rate of consumption must be regulated with precision if a proper deposition is desired.

In the present invention these disadvantages are obviated by making use of the fact that lead is relatively immune from attack by sulphuric acid base or chlorine ions and accordingly lead is used as the anode in combination with a special bath whose characteristics will be pointed out below.

In the preferred embodiment of my invention an electrolyte is used which contains a mixture of chromic acid and chromium sulphate and other suitable chromium salts such, for example, as chlorine compounds of chromium as the principal constituents and carbolic acid, boric acid-or glycerine as the auxiliary or addition agent. With a solution of the character described, the lead will precipitate owing to the presence of the sulphuric acid base or chlorine ions and it will therefore not interfere with the operation of the bath. I

Using a lead anode and the addition agents herein mentioned, I have found that the following bath gives satisfactory results although it is to be understood that the proportion of the ingredients used may vary without departing from the scope of the invention as pointed out with particularity in the appended claims:

Per cent.

.(lhromic acid 5 to'10 Chromium sulphate 5 to 15 Boric acid 5 As hereinbefore stated, glycerine or carbolic acid mav be used in lieu of the boric acid as an addition agent.

It will be found that the metallic chromium deposited from the bath described above will be dense, firmly adherent, and capable of withstanding exposure to high temperatures.

\Vhat I claim as new and desire to secure by Letters Patent of the United States, is 1.- A process for the electro-deposition of metallic chromium consisting in conducting an electrolyzing current through a solution containing chromic acid 5 to 10%, chromium sulphate 5 to 15%, boric acid 5% from a lead anode to the article to be coated as a cathode. 2. A process for the electro-deposition of chromium which comprises supplying current from a lead anode through a solution containing 5 to 10% chromic acid, 5 to 15% chromium sulphate and approximately 5% of an addition agent to the article to be coated as a cathode.

In witness whereof, I have hereunto set my hand this 9th day of July, 1925.

EIJI SUZUKI.