US1565495A - Process by which aluminum metal and its alloys may be applied to ferrous metal - Google Patents

Description

Patented Dec. 15, 1925.

UNITED STATES PATENT OFFICE.

CARL W. PFEIL, OE GREENBANK, WASHINGTON.

PROCESS BY WHICH ALUMINUM METAL AND ITS ALLOYS MAY BE APPLIED TO FEIQBOUS METAL.

No Drawing.

To all whom it may concern:

Be it known that- I, CARL W. PFEIL, a citizen of the United States, residing at Grreenbank, in the county of Island and State of Washington, have invented Processes by Which Aluminum Metal and Its Alloys May be Applied to Ferrous Metals, of which the following is a specification.

My invention relates to the art of providing metals with a protective coating, as for instance, applying a coating of a rust and acid resisting metal to a baser metal.

The object of. my invention is to apply a metallic protective coating in such a manner as to secure a joining of the protective and the base metals in that close and intimate manner that the protective coating cannot be sealed off, the union between the metals being'more in. the nature of an alloying of the two, rather than an adhesive contactbe-' tween them. I

The process employed by me in carrying out my invention 'will be hereinafter described and the features thereof which are believed to be novel will be particularly defined by the claims.

. While the field for the use of my process is probably greater in the application of an aluminum coating to sheets of a ferrous metal for the 'manufacture of a product usable as a substitute for tin plate, it is nevertheless adapted to the application of protective alloys having an aluminum com-v ponent and also for application of such a protective metal coating to cast and wrought metals irrespective of their thickness and bulk. I will herein more specifically describe the application of my invention to providing an aluminum coating for sheet metal; it is, however, to be understood that this is not done as a'limitation to this use only, but only as illustrative of the principles to be employed and the manner of securing the ,desired results.

It has been rather generally held that proper welding or soldering of aluminum'to aluminum, or to other metals, is prevented by an oxide film which promptly forms upon a newly formed surface of aluminum. This theory of an oxide film may or may not be correct. I have, however, found that if aluminum be reduced to very fine powderlike particles and during such reduction'a- Application filed May 1,

- point 0 1922. Serial No. 557,705.

and the aluminum or aluminum alloy is ma-' terially facilitated or controlled by the electric relationship existing between the two and by electric action occurring when theyare brought into contact.- Such electrical action is also heat.

I have noticed that success irr getting a welding or alloying union between the base and coating metal appears to depend very much upon the base metal being electronegative to the coating metal. It would-appear probable that an action occurs which is of an electrolytical character and this supplements the ordinary fusing action of heat.

The surface thus formed has the protective and resistant qualities of the material formingthe coating and cannot by ordinary means be separated from the metal which forms the base.

As the protective material for the fine particles of the coating metal I have employed oils, fats, waxes, fatty acids, resins and the like, and other substances and combinations thereof capable of forming airexcluding films and of being volatilized or otherwise eliminated or dissipated by heat at tem eratures lower than the melting tithe coating metal used. The ideal is a substance or mlxture which will not be dissipated until the fusing temperature is nearly reached.

This protective material may be of animal, vegetable or' mineral origin. I have found a large number of products to be adapted for such use. The chief requirement appears to be their ability to coat the metallic particles with a thin film which excludes the air and the quality of being volatilized or dissipated by heat at temperaprobably intensified by the tures below that of fusing of the coating metal. I

Among the substances which I have found adaptedrto this use are the mineral oils, of which kerosene is a type; mineral waxes, of which para'fiin is, a type; vegetable. oils, of which palm oil is a type. Or I may use combinations of two or more of suchsubstances as the protective film forming material, this including chemicals such as ammonium chloride.

In preparing the metal for the coating material I finely divide and grind, or otherwise pulverize, it in a bath of the protective film forming material. The means employed in grinding the metal is immaterial if it will reduce it to fine particles. It is desirable that the particles be reduced as fine as possible. The result of this work is a colloidal-like sludge or paste which should contain the largest possible amount of metallic particles. I

In carrying out the coating process this product is heated to a temperature which will vary with the metal contained therein and with the kind of film forming material which has been used. The temperature should be as high as possible, less than that which will volatilize or otherwise eliminate the film forming material, or less than the fusing point of the metal, depending upon which is the lower.

The body of the metal to be coated is heated to a temperature in excess of that of the bath and is coated either by dipping the heated metal in the bath or by applying-the bath to the heated metal, as best suits the conditions. If the body to be coated isdipped in the bath, it is left therein only momentarily. The heat of the metal base, being higher than that of the bath'dissipates a portion of the film forming agent. The

metal content of the bath adheres as a thin coating to the base.

The metal body ,being coated is further heated after removal from the bath, thus completing the driving oif'of the film forming materials from the compound which has adhered to the base. This coating has apparently been alloyed with the base so as to secure the coating to be in effect an integral part of the base. There isno cleavage plane between the two which will permit separation.

The protective coating may be applied to the base or article to be coated, by brushing or flowing it thereon. The conditions as to temperatures should, however, be essentially the same. The heat and temperature needed to evaporate or drive off the protective" film must be applied, in part at least, after the film has been a plied. The fundamental temperature con itions which are desirable or necessary are, first, that the temperature of the metal bath be less than that which will volatilize or drive off the protective film forming material and that of the metal base after the application of the film be such as will volatilize or drive ofi this film forming material. 7

The temperature of the bath and of the metal base at the time of a plying the coating contributes to the perf ction of the union between them, a higher temperature producing better results than a lower temperature. I also prefer that the metal base be of a temperature somewhat above that at without immersion, or by partial immersion,

it is possible to apply a protective coat locally. The surface after coating may be rolled, burnished or given any treatment which may be given to metals coated by other processes.

I have found a coating thus applied to be more perfect in its continuity than an ordinary tinplate coating. It does not seem to ossess the microscopical uncoated points or holes in the protective layer through which acids may act upon the metal base and rust take place. I 1 'i I have found this process to be applicable to applying coatings of aluminum or alloys in which aluminum forms a material part. The process is, however, not limited to use with these metals alone. One of the chief applications of this process is the applicaties against the action of acids, corrosive agents and heat is superior to that of tin plate, both by reason of the superior resistant quality of aluminum to such agents and by reason of its superior mechanical condition in its freedom from minute erforations and its higher resistance to eat and also its non-poisonous qualities.

Such coatings are superior to tin plate in this that heating to a temperature less than the melting point of aluminumm will not cause loosening of the coating from the base as may be done with tin plate. There ap pears to be an inter-penetration or alloying of the-coating and base metal which prevents separation and is not affected by any heat whlch will not actually melt the coating metal. c

The essential feature in the success of welding where at least one of the metals is aluminum or an aluminum alloy appearsto be the provision of a fresh surface on the aluminum and protecting it from the action of the air by giving it a protective film, as of an oil or wax or other air-excluding substances which has a hi h dissipating point, and then eliminating t is film at the time of joining the surfaces, whereby the aluminum or a uminum alloy is presented to the visible film formed thereon by the action of air whereby it readily forms atrue welding union.

While I have chiefly herein dwelt upon the application of a very thin coating of the protective metal and by the use of the protective metal in the form of powder, the

same principle is believed to apply to the union. of distinct sheets, the surfaces to be welded being first treated by grinding or otherwise removing a surface film and protecting this by a protective film until the welding action occurs.

Commercial aluminum powder -may be used by my process but the results are not as satisfactory. A coating made by using commercial aluminum powder will scale, especially when plates so coated are bent or seamed.

' What I claim as my invention is i 1. The process ofproducing a protective coating of one metal upon another which consists in very finely dividing the coating metal in a bath of a film producing material 'which may be driven off by heat, applying the product thus formed to the metal to be protected and heating to a temperature which will drive off the protective film and fuse the coating and base metal.

2. The process of applying an aluminum coating to a base metal which consists in very finely dividing the aluminum in a bath of an air-excluding film-producing material,

applying the compound thus formed to the metal, to be coated and heating.

'3. The process of giving a metal a protective coating of another metal'which consists in grinding the coating metal while subjected to a film producing agent, heating the-product thus produced to a temperature below that which will dissipate the film, heating the metal to be coated to a temperature higher than that required to dissipate the film and then applying the coating product to the metal to be coated.

4. The process ofapplying an aluminum alloy coating to'another metal which consists in finely reducing the aluminum alloy metal while subjected to an air excluding film-producing agent, heating this product to a temperature below that-which -will dissipate the film producing'agent, heating the metal base which is to be coated to a temperature sufficiently higher to dissipate the film and applying the coating product to the base. V

5. The process of applying an aluminum alloy coating to a ferrous metal which consists in finely dividing the coating metal under air-excluding conditions and while still subject to such air-excluding conditions heating it and the metal to be cdated and bringing the two together.

6. The process of coating a ferrous metal with aluminum which consists in grinding the aluminum under a bath of an air-extion temperature, applying a coating of the resulting mixture to the metal to be coated and heating to -a temperature which will volatilize the air-excluding medium used eluding medium having a high volatilizaing film and causing the coating metal to adhere to the base by the action of heat.

8. The process of applying a protective aluminum coating to a base metal which consists in simultaneously finely dividing the aluminum and applying thereto as divided an air-excluding film, applying said product to the metal tobe coated and then eliminating the coating film and causing the aluminum to adhere to the base by the application of heat'thereto;

9, The process of securing welding union with aluminum which consists in removal of a surface film from the aluminum and at the same time providin with an' air-protective film of a material which can be disposed of by heat at a temperature not exceeding the melting point of aluminum, applyin the aluminum to the surface to which it is to be joined and heating to a temperature sufiicient to dissi ate said protective film and to produce wel ing umon.

10. The process of securing welding union with aluminum which consists in giving the aluminum a fresh surface by abrasion andat the same time giving it an airprotective film which may be dissipated the new surface by heat at a temperature slightly lower than the welding heat for aluminum, applying the aluminum to the surface to whichit is :GARL- w. PFEIL,