US1607676A - Process for obtaining metal coatings on articles of aluminum and aluminum alloys - Google Patents

Description

the action of a weak electric current in an dipping in a solution of the fluoride of the:

Pasta Ne 1926.

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PROCESS FOR OBTAINING METAL COATINGS ON ARTICLES. 01 ALUMINUM All!) ALUMINUM ALLOYS.

No Drawing; Application filed January 15. 1926, Serial No. 81,580, and in Germany October 29, 1924.

It is known to coat aluminum articles very thinly with copper, on which a thicker coating of nickel'or the like can be electrically deposited without the danger of the peeling Off which occurs when the nickel is deposited directly on to the aluminum. To effect such thin coating with copper the aluminum articles, after they have been separately freed rom grease, are exposed to acid bath of a copper salt.

' In the art of coating. metals it has also been proposed to coat aluminumwith a preliminary layer of copper, zinc, or tin, by

coating metal and potassium tartrate. It has been further proposed to coat-aluminum preliminarily with zinc by dipping the aluminum in sulphate of zinc and ammoniuin tartrate.

-' muth, silver,

',mixture of the salts- It has, also been proposed to coat alumi- 1 num directly with a desired metalbydipping ,in'a bath, which maybe heated to hasten the action,' "composed of ammonium coating metal,the bath being rendered alka line by the addition of liquid or aqua animonia, or ammonium carbonate. A mixed coating may' be obtained by using asuitab'le of the coating metals. According to the present invention a usable metal coating is obtained on alumi num both without preliminary freeing from grease and without employment of electric current byimmersion in a bath-oi hot. salt solution of alkaline reaction, which contains salts of copper, nickel, cobalt andzinc,

bisgold and tin and in addition only potassium carbonate and potassium bicarbonate alone, or mixed with a. corresponding salt or salts of sodium. Watersoluble-oxygen liberating compounds in parmanganese, iron and-chromium, lead,

.ticular water-soluble chromate canbe added- 45 to the bath.

dropper coatingv obtained in the presence of alkaline-carbonate has a dark colour. A bright andlclean metallic deposit is obtained- ,if an oxidizing agent, in particular otassiumbiohromate, 1s added to the bat A bath which has chloride and the chloride or the salt of the coating duralumin,

proved extremeigegood m use contains in' 2.5 litres of water 25 gms.

.of crystalline copper sulphate, 25 gms. of potassium carbonate, 25 gms. .of sodium bicarbonate and 10 gms. of potassiumbichromate. Instead of 10 gms. of potassium bi- .chromate up to 25 gms. of a 3% solution of hydrogen peroxide can" be used. Instead of potassium carbonate and sodium bicarbonate a correspondingly greater quantity'of potassium bicarbonate alone can be used.

In this bath the copper. sulphatecan'be replaced by, eqiiivalent quantities of inorganic salts of heavy metals, so that a firmly adhering deposit can he obtained direct, that is without preliminary deposit of a layer of copper.

In this way it is possible by using the sulphate of nickel. cobalt,or manganese, iron, chromium, ing metal'coatings on aluminum. The same method succeeds with nitrates of lead. bismuth or silver. The silver coatin is at first bright, but with longer boiling ta es on theknown as so-called oxidized 'tained without the use of oxidizing agents.

The above mentioned metallic salts can also be used mixedto obtain mixed coatings. For example a mixed deposit of chromium or zinc to. produceffirmly adher-.

obtained, which however bright appearance of the and silver can be obtained on soft aluminum by using a solution containing in 1 litre of water, 10 gms. of chromium sulphate, 2 gms. of silver nitrate, 10 gms. of ,potassium oars bon'ate, 3.3 gms. of sodium bicarbonate, and 3.3 gms.. of potassium bichromate. For three times the quantity of each constituent lv n (e. g. 10;2o, is added. to the metallizin'g baths, Y

Instead of articles of pure aluminum,- those made of aluminum alloys, e. g.- dura-' lumin, can be coated.

It will be noted from theabove descripis used per litre. It has been found that the coatings are brighter written description theprocess hasth advantageithat neither the electric current nor prior cleaningis necessary.

In certain of the claims the term a substantial amount of has been used before the name of certain ingredients or compounds. Such terms have been used to distinguish from cases in which mere traces of ('orinconsequential amounts of) the said substances may. possibly havebeen present asimpurities in other substances used.

What I claim is: 1. The process for producing'metal coating on aluminum or an aluminum alloy without substantial previous cleaning which comprises subjecting a surface thereof without application of electric current to'the'action which comprises subjecting a surface thereof without application of electric current to 4 electronegative vto aluminum.

of an aqueous liquid togwhich has been added a bicarbonate of an alkali metal and a simple salt of a metal which is electronegative to aluminum.

' 2.- The process for producing metal coating on aluminum or an aluminum alloy which comprisessubjecting a surface thereof to the action of an aqueous liquid to which has been added a bicarbonate of an alkali metal and a salt of a metal which is. 'electronegative to aluminum. a

' 3. The process for. producing; metal coating on alumin or an aluminum alloy the action of an aqueous liquid to which has been added an alkali carbonate, 'an alkalibicarbonate and a salt of a metal which is to the action of an aqueous liquid containmg potassium bicarbonate and a salt of a a metal whichis electr'onegative'toialuminum.

' ing on aluminum or an;

6. The process for producing metal coataluminum alloy 'which' comprises subjgting, a surface thereof to'theaction of an aqueous liquid to which has-been added carbonate ,of an alkali metal, a substantial amount of bicarbonate of an alkali metal,'at least-one of said alkali metals being potassium, and a salt of a metal which is electronegative toalumiilinnf.

7 The process for prjoduciiig metal coating on at umfor aluminum alloy which comprises subjecting a surface thereof a without application of electriccurrent to the metal which is electronegative to producing-metal coatmg onv alummumor an aluminum to which has been added a bicarbonate of an alkali metal and a salt of a metal which is electronegativeto aluminum.

8. The process for producing metal coating on aluminum or an aluminum alloy -which compr ses subjecting a surface thereof to the action of an aqueous liquid to which has been added a' substantial amount of bicarbonate of an alkali metal, and oxygen liberating compound and a simple salt of a metal which is elec'tronegative to aluminum.

9."The process for producing metal. coating fon aluminum or an aluminum alloy Ywithout substantial prior cleaning which comprises subjecting a surface thereof to the action of added a substantial amount of bicarbonate of potassium, an oxygendiberating agent,

and salt-0f a metal which is electronegative to aluminum.

10. The process for producing metal coating on aluminum or an aluminum alloy which-comprises subjecting a surface thereof to the action of an aqueous liquid to which has been added .a. substantial amount of potassium bicarbonate, an oxidizing agent and a salt of a-metal which is electronegative to aluminumr 11. Theprocess for producingmetal coating on aluminum. or an aluminum alloy .which comprises subjecting a surface thereof to the action of an has been added a carbonate of an alkali metaqueous li uid s which a1; a bicarbonate of an alkali -metal at least one of said alkali oxygen liberating compound 12. The-.process for producing metal coat- .ing on aluminum or an aluminum alloy which comprises subjecting a surface thereof to the action of an aqueous liquid to which has been added a. bicarbonate of an alkali metal, an oxygen liberating agent and a salt of ametal-electronegative to aluminum, p I p 13. The process for producing metal coatmg onaluminum or an aluminum alloy which comprises subjecting a surface thereof to the action of an aqueous liquid to which has been added a bicarbonate of an alkali metal. a carbonate of an alkali metal,

an oxygen liberating compound and a salt of a metal which is electronegative to aluminum. V

14. The process ior'producing metal coating on-jaluminum or analuminum alloy which comprises subjecting 'the surface thereof to the action of an aqueous liquid added potassium bicarbonate, an. oxidizing compound, glycerine and a saltof a metal which is electronegative to aluminum,

15.;The process for producing metal coats ing on 3 aluminum I which comprises subjecting a surface. thereof metals being potassium. an

, and a salt of a aluminum.

or an aluminum alloy an aqueous liquid to which'has been I H sium,-an oxygen liberating compound,

alkali bicarbonate and a H which is elect-ronegative to 20. A bath mixture for coating aluminum or. an aluminum alloy by contact with an aqueous mixture-thereof containing a carlbonate of an alkali metal, a substantial, g -famount of a'bica-rbona te of an alkali metal,

which comprises subjecting a surface thereof to the action of an aqueous liquid to which has been added a bicarbonate of'an alkali metal, an oxygen liberating agent, glycerine, and salt of a metal which is electronegative to aluminum.

17. A bath mixture for coatingaluminum or an'aluminum alloy by contact 'with an aqueous mixture thereof containinga sub-' stantial amountof a bicarbonate of an alkali 0 metal and a'salt of a metal which is electronegative to-aluminum. a

'18. A bath mixture for coating aluminum or an aluminum alloy by contact with an aqueous mixture thereof containing a substantial amount of potassium bicarbonate and a salt of a metal which is ele'ctronegative to aluminum.

19. A bath mixture for coating aluminum or an aluminum alloy by contact with an 0 aqueous mixture thereof containing-an alkali carbonate, a substantial'amount of an aluminum.

at least one of said alkali metals being potassium, and a salt ofa metal which is electronegative to aluminum. i

, .21. A bathv mixture for coating aluminum or an aluminum allog by contact with an I aqueous mixture thereof containing a bicary salt of a metal" bonate of an alkali metal, an oxygen liber. ating compoundand a salt of a metal which is electronegative to aluminum. I

22. A bath mixture for coating aluminum or an aluminum alloy by contact with anaqueous mixture thereof containing potassium bicarbonate, an oxygen liberating compound and a salt of a metal which is electronegative to aluminum.

23. A bath mixture for coating aluminum or an aluminum alloy by contact with an aqueous mixture thereof containing a substantlal amount of potassium bicarbonate, an

alkali chromate compound, and a salt of a metal which is electronegat ve to alumlnum.

, 24. A bath mixture for coating aluminum oran aluminum alloy by contact with an aqueous mixture thereof containing a carbonate of an alkali metal, a substantial amount of bicarbonate of an alkali metal, at least one of said alkalimetals being potassium, an oxygen liberatingcompound,

and a salt of a metal which is electronegao tive to aluminum. 7

25. Abath mixture for coating aluminum or an aluminum alloy by-c'ontactwith an aqueous mixture thereof containing a carbonate of an alkali metal, a substantial amount of bicarbonate of an alkali metal, at least one of said alkali metals being potassium, an alkali chromate compound, 7 and a salt of a metal-which is electronegative to aluminum.

2(5. A bath mixture for coating aluminum I or an aluminum alloy by contact with an. 80.

aqueous mixture thereof cont-ainin' acar bonate of an alkal metal, a su stantial amount of bicarbonate of an alkali metal,

an oxygen liberating compound and a salt of'a metal which is electronegative to aluminum.

' I In testimony whereof I aflix' my signature.

,BIOHUMIL JIR'OTKA.