US1515658A - Process for coating aluminum - Google Patents

Description

. To all whom it may concern:

attests r as corn, or sournnen, massacnnsnrrs.

rnocnss non ooarme anunnwm.

No Drawing.

ish for, metallic articles and to improved methods and processes of obtaining the same.

The principal object of my invention is to coat or plate a metallic ob ect quickly and inexpensively without the use of the usual electrical current in such a way that the coating will be permanent and wear-resisting, and so that it maybe either polished for a clear luster finish oroxidized for the darker finishes as desired.

Another object is to obtain desirable metallic finishesin a minimum of time and at a minimum of expense.

One of the principal objects of the invention is to provide a suitable metallic coating or aluminum which may be either polished or oxidized as desired.

Another object of the invention is to provide such permanent metallic finishes by the bath or di method as contrasted with the longer and more expensive method of the electric current.

The difiiculties in plating aluminum have long been known and many endeavors have been made to accomplish it, but so far, none of these methods has proven commercially successful, especially when applied to the so-called commercial aluminum. The trouble seems to have been that the. alumi num quickly oxidizes and becomes coated sidera le time, from twenty to thirty min- .utes and longer, to form a coating; and thisobviating coating has not been rmanent due to the oxidizing film" underlying. it. In my process the coating is practically instantaneous, thus the oxidizing film referred to above.

" Oneof the most popular and satisfactory Application f l ed December 4, 1919. Serial No. 342,515.

finishes is that known as the gun metal finish, which has usually been obtained by a heat process which is long. and expensive. It is possible with this process, to obtain substantially instantaneously and very inexpensively, the desired plating. When applied over aluminiun it makes a most desirable article. It is, therefore, one of the ob- I jects of the invention to overcome these dllllCllllIlBS in the treatment of aluminum and other metals and to producen finished article that shall possess the desired characteristics.

Briefly stated my process is as follows, although these steps may be alternated and changed without affecting the final results, the preferred form only being described here by way of illustration. It will be understood that the s'teps and their order may be departed from without departing from the spirit of the invention as expressed in the claims.

The aluminum article to be plated is first subjected to a cleansing operation in order to thoroughly prepare the same, in order that the article may take on a substantial plating. In cleansing the aluminum article, it is first immersed in a solution of substantially one part of sal soda to substantially thirty-two parts of water, by weight, the solution being charged with a substantial steady currentof electricity, and the. article is maintained immersed ntil it is thoroughly cleansed. The fact is the electro-chem-i- .ca-l action of the solution rapidly cleanses the aluminum article in avery short time and renders the surface thereof 1 more 'sus ceptible to a substantial permanent plating. After the article is cleansed, it is removed from the electrified cleansing solution and-is immersed in a bath of cdp er cyanide saturated solution which is sub ected to heat substantially one hundred. and ninety degrees Fahrenheit, thus generating a galvanic ,ac-

tion which, due to the surface receiving its preparation from the electro-chemical action, the aluminum article will take on a substantial permanent plating. At the time of immersing the article in the copper c a nide saturated solution, the. time consume is. substantially one-ha1f aminute, itdepend ing entirely on the of the article, and

durin this intro uced. V

- If desired'silver nitrate can be used instead ofthecopper cyanide. The article can step, there is no outside current 1 immersed in another bath, a cold solution of liver of sulphur and leave it there about one-half minute. It takes longer in Winter than in summer. No electric current is introduced. This sulphur solution oxidizes the copper coating or other metal, as the case may be, turns it dark until it has the appearance of un metal. It produces a very beautiful finish of high luster of the desired color, and which needs notbe further polished or buffed. The article is ready for use as it comes from the sulphur solution.

In the case of copper, the dark finish is a sulphide .of copper, the sulphur solution simply oxidizes the copper coating; there is nothing but the base metal underneath.

Articles treated with this process receive highlysatisf actory results, particularly with aluminum.

From the foregoing description it will be seen that there has been produced, metallic articles with the desired finishes in a rapid, expeditious and inexpensive way.

After applying a layer of copper on the article, it isalsopossible to plate the copper layer with other metals, such as gold, silver, nickel, etc.

In employing the term sal soda in the foregoing specification it is to be understood that I have in mind thesubstan'ce listed in U. S. Official Pharmacopaeia as crude sodii carbonas monohydratus, and that in referring to liver ofsulphur I mean the substance so referred to in the book aforesaid and also referred to in said book, page 30, as crude potassa sulphurata, the commori nomenclature of the art havin been used throughout the specification and claims for more ready understanding by the ordinary person in the art of the particular substances under consideration.

I claim:

1 A process for plating aluminum articles, first consisting in preparing the article by immersing the same in a solution of substantially one part sal soda and substantially thirty-two parts water, by weight, charging the solution with a substantial steady current of electricity, the electro-chemical action of the solution rapidly cleansing the aluminum article, rendering the surface thereof more susceptible to a subsequent substantial permanent plating, then removing the article from the electrified cleansing solution, and immersing it in a bath of copper cyanide saturated solution which is subjected to heat substantially one hundred and ninety degrees Fahrenheit, thereby generating a galvanic action which, due to the surface having previously received its preparation from the electro-chemical action, the aluminum article will take on a substantial permanent plating.

2. A process for plating aluminum articles, first consisting in preparing the article by immersing the same in a solution of substantially one part sal soda and substantially thirty-two parts water, by weight," charging the solution with a substantial steady current of electricity, the electro-chemical action of the solution rapidly cleansing the aluminum 'article, rendering the surface thereof more susceptible to a subsequent substantial permanent plating, and immersing it in a bath of copper cyanide saturated solution which is subjected to heat substantially one hundred and ninety degrees Fahrenheit, thereby generating a galvanic action which, due to the surface having previously received its preparation from the electrochemical action, the aluminum article will take on a substantial permanent plating, removing the article from the cyanide solution'and subjecting it to a polishing process to give the article a luster finish, and finally oxidizing the polished surface thereof.

In testimony whereof I have aflixed my signature, in resence of two witnesses.

. T OMAS CHARLES COLE. 7

Witnesses:

HARRY H. STYLL, Anion G. HASKELL.