US1971240A - Method of coloring aluminum - Google Patents

Description

4 Patented Au 21, 1934 i 1,971,240

, UNITED STATES PATENT OFFICE 1,971,240 METHOD OF COLORING ALUMINUM Martin Tosterud, Arnold, Pa., assignor to Aluminum Company of America, Pittsburgh, Pa., a corporation of Pennsylvania No Drawing. Application December 1'1, 1930,

, Serial No. 502,987

4' Claims. (01. 148.-6)

This invention relates to the treatment of alkali carbonates and soluble dichromates, and 1 aluminum and aluminum alloy surfaces to prouse both in the preferred practice of the invenduce thereon a colored coating. The term alumition. A solution of any alkali carbonate and any num, as used herein and inthe appended claims, soluble dichromate may be used, but I prefer 5 includes that metal in every degree of purity and a solution of sodium carbonate and potassium 60 all alloys thereof containing sufficient aluminum dichromate containing about 0.5 to 6 per cent of to permit the formation of a suitable oxide coatthe carbonate and about 0.1 to l per cent of the ing on the surface of the article, as explained dichromate, and! have had excellent results with hereinafter, that is to say, alloys in which the about 2 per cent of the former and about 0.5 10 aluminum content is 50 per cent, approximately, per cent of the latter. Simple immersion of the 65 or more. piece to be coated in the treating solution, or The many and varied uses of aluminum in both spraying it with the solution, is in general sufthe practical and decorative arts have made very ficient without the application of any external desirable the development of suitable process by electrical energy. which aluminum surfaces may be colored, and the After the desired oxide coating has been formed 7c I provision of such a process is one of the objects on the aluminum surface I treat the coated metal, of my invention. A further object is to provide say by immersion or spraying, with a solution a process which is simple in operation and which of a soluble salt of permanganic acid. While I may be practiced .on a large scale with reasonable prefer to use potassium or sodium permanganate, cost and a minimum of difiiculty. any soluble salt of permanganic acid may be used is In the course of an extensive investigation f r h p rp T concentration of h p directed toward the development of suitable procma ga Solution (1085 ot appear to be a 65595 and th d for th coloring f th critical factor, as I have found that solutions faces of aluminum and its alloys, 1 have 115- containing as 11131316 as 1 per cent Of the soluble covered that certain colors are particularly dif- Compound Compounds used, and Solutions 80 ficult to obtain on aluminum. Thus the pro which are completely-saturated, will produce the duotion of a, brown color, which color is often COlOI'S desired. I prefer to use concentrated so1udesired on aluminum surfaces, is one which p tions, however, since I have observed that the gents particular difiioulty S h @1013 h adsorption of the solution by the oxide coating can be readily obtained by my present i ti is more rapid than with dilute solutions. I have 5 which, briefly stated, comprises first treating the further determined that the temperature of the a1uminum 31131913 to provide on its surface a, solution (if the salt Of permanganic acid at the hard and to a substantial degree adsorbed oxide e at W h the Oxide-coated metal is introcoating and thereafter treating this coating with du therein is not a governing m t r and that a solution of a soluble salt ofpermanganic acid. Satisfactory c010rs may be P e Whether the on According to the preferred practice of th solution be cold or hot. The use of a hot solution invention the aluminum article is first treated to facilitates d y f the article afterwards. produce upon its surface an oxide coating which As has hereinabove been mentioned, the color is hard and dense and which has sufficient adpr d d on h l m n m r al mi um all y sorbent qualities to retain, when immersed in or urf c in h pr t of my novel method is e equivalently treated with a liquid, an apprebrown or some shade thereof, and l have found ciable quantity of such liquid within and upon that the depth of color and the particular shade it. The term oxide coating, as used herein, desired may be regulated by varying the thiclz1- is a well known designation in the art to deness of the oxide coating which is originally 5 scribe a layer of aluminum oxide artificially proproduced on the aluminum or aluminum alloy mg duced on the aluminum or aluminum alloy sursurface. If the aluminum, in the oxide-coating faces by chemical treatment, with or without process, is immersed in the solution for a brief the use of externally applied electrical energy, period, a thin film of oxide coating will be obbut the term does not include the thin film of tained. With longer immersions, the thickness 0 aluminum oxide which is naturally formed upon of this oxide coating increases and in thisway 105 the metal by contact with the air. a satisfactory adherent, adsorbent oxide coating In the various methods of producing oxide of the desired thickness may be produced, adeeper coatings, there are certain reagents which i have color and darker she de being, in general, profound particularly effective for the purpose duced with a heavy coating than with a thin of my present invention. These reagents are coating. m

As a specific example of the method in which my invention may be practiced, an aluminum article was immersed for 10 aqueous solution containing 20' grams per liter of sodium carbonate and 5 grams per liter of potassium dichromate. -At the end of this time, the metal was removed from the solution, washed, and while in a moist condition immersed in a hot saturated solution of potassium permanganate for a period of 2 to 5 minutes. The article, after removal from the permanganate solution and drying, had on its surface a brown color which, for all practical purposes, was stable and permanent and completely adsorbed in the oxide coating.

I am aware that it has been proposed to impart a brown or black color tov porous articles by successive treatments with separate reagents, one an oxidizable compound and the other potassium permanganate to oxidize the same. In my invention I produce the brown color by treating the oxide coating with potassium permanganate or other permanganic compound without prior, or subsequent treatment.

I do not claim herein broadly the coloring of aluminum by adsorbing, in an adsorbent oxide coating on the surface of the metal, successive reagents which react in the coating to precipitate a colored inorganic compound, but .do so in my copending application Serial No; 474,665, filed August 11, 1930.

It is to be understood that the invention is not limited to the specific details herein described M No- 1.911.240.

to 15 minutes in an CERTIFICATE OF CORRECTION.

but may -be carried out in other ways without departure from its I claim- 1. The method of permanently coloring the surfaces of aluminum or aluminum alloy articles, comprising treating the metal surface with a solution containing an alkali carbonate and a soluble dichromate to form thereon an adsorbent oxide coating, and thereafter without further treatment impregnating the coating with a soluble salt of permanganic acid.

2. The method of permanently coloring the surfaces of aluminum or aluminum alloy articles, comprising forming onthe metal surface an adsorbent oxide coating, and thereafter without further treatment treating said surface with a solution of potassium permanganate, for the purpose herein described.

3. The method of permanently coloring the surfaces of aluminum or aluminum alloy 'articles, comprising treating the metal surface with a solution containing an alkali carbonate and a soluble dichromate to form thereon an adsorbent oxide coating, and thereafter without further treatment treating the coating with a solution'of potassium permanganate, for the purpose herein described.

4. The method of permanently coloring aluminum or aluminum alloy by impregnation of an spirit.

adsorbent oxide coating previously formed on the surface of the metal, which consists in immersing the article in a solution of a salt of permananic acid. MARTIN TOSTERUD.

magnet 21.

MARTIN TOSTERUD.

It is hereby certified that error appears in the printed specification oftheabove numbered patent "adsorbed" read adsorbent; this correction therein that the Patent Office.

requiring correction as mum: Page 1, line": 33.1w

and that the" said Letters Patent should be read with the same may conform to the record ofthe case in Signed and sealed this- ZSthday of septelnber, A. o. .1934. l

(Seal) 4 Leslie Frazer Acting Commissioner of Patents,

As a specific example of the method in which my invention may be practiced, an aluminum article was immersed for 10 aqueous solution containing 20' grams per liter of sodium carbonate and 5 grams per liter of potassium dichromate. -At the end of this time, the metal was removed from the solution, washed, and while in a moist condition immersed in a hot saturated solution of potassium permanganate for a period of 2 to 5 minutes. The article, after removal from the permanganate solution and drying, had on its surface a brown color which, for all practical purposes, was stable and permanent and completely adsorbed in the oxide coating.

I am aware that it has been proposed to impart a brown or black color tov porous articles by successive treatments with separate reagents, one an oxidizable compound and the other potassium permanganate to oxidize the same. In my invention I produce the brown color by treating the oxide coating with potassium permanganate or other permanganic compound without prior, or subsequent treatment.

I do not claim herein broadly the coloring of aluminum by adsorbing, in an adsorbent oxide coating on the surface of the metal, successive reagents which react in the coating to precipitate a colored inorganic compound, but .do so in my copending application Serial No; 474,665, filed August 11, 1930.

It is to be understood that the invention is not limited to the specific details herein described M No- 1.911.240.

to 15 minutes in an CERTIFICATE OF CORRECTION.

but may -be carried out in other ways without departure from its I claim- 1. The method of permanently coloring the surfaces of aluminum or aluminum alloy articles, comprising treating the metal surface with a solution containing an alkali carbonate and a soluble dichromate to form thereon an adsorbent oxide coating, and thereafter without further treatment impregnating the coating with a soluble salt of permanganic acid.

2. The method of permanently coloring the surfaces of aluminum or aluminum alloy articles, comprising forming onthe metal surface an adsorbent oxide coating, and thereafter without further treatment treating said surface with a solution of potassium permanganate, for the purpose herein described.

3. The method of permanently coloring the surfaces of aluminum or aluminum alloy 'articles, comprising treating the metal surface with a solution containing an alkali carbonate and a soluble dichromate to form thereon an adsorbent oxide coating, and thereafter without further treatment treating the coating with a solution'of potassium permanganate, for the purpose herein described.

4. The method of permanently coloring aluminum or aluminum alloy by impregnation of an spirit.

adsorbent oxide coating previously formed on the surface of the metal, which consists in immersing the article in a solution of a salt of permananic acid. MARTIN TOSTERUD.

magnet 21.

MARTIN TOSTERUD.

It is hereby certified that error appears in the printed specification oftheabove numbered patent "adsorbed" read adsorbent; this correction therein that the Patent Office.

requiring correction as mum: Page 1, line": 33.1w

and that the" said Letters Patent should be read with the same may conform to the record ofthe case in Signed and sealed this- ZSthday of septelnber, A. o. .1934. l

(Seal) 4 Leslie Frazer Acting Commissioner of Patents,