US2161104A - Metallic coating material and method of applying the same - Google Patents

Description

Patented June 6, 1939 METALLIC COATING MATERIAL AND METH- OD OF APPLYING THE SAME George S. Smith, Oakland, Calif.

No Drawing. Application November 13, 1936,

Serial No. 110,774

6 Claims.

The present invention relates to an improved metal-like coating material that may be applied by brush or spray, or in any manner suitable for the application of ordinary paints, to any type of surface capable of being painted. The present application is a continuation in part of my application entitled Metal coating, Serial No. 715,247, filed March 12, 1934.

Among the known methods of producing a 10 metal or metal-like coating are those in which the metals of the coating material are fused by the application of heat to the surface to be coated, electrically deposited, or rubbed onto the surface in compounds containing the metal to be deposited. These methods are limited in their application to metal surfaces only. They require the metal surface to which they are to be applied to be brightened or deoxidized through the use of a flux, or by sand-blasting, or other cleaning operation, and for this reason are impractical for many uses, and particularly where large surfaces are to be coated.

Other known methods include the application of a metal powder to a surface in a paint-like binding material, such as silicate of soda, varnish,

or organic binders. These methods have the disadvantage that the said binding material remains in dried state on the surface and co-mingled with the particles of powdered metal, with the consequence that the resulting coating has many of the undesirable characteristics of the binding substance, the endurance and resistance of which are inferior to those of pure metal coatings.

It is an object of the present invention to provide a metal-like inorganic coatingmaterial and a method of applying the same that is applicable to any type of surface, regardless of the texture thereof.

A further object of the invention is to provide a metal-like coating material and a method by which it may be applied in the manner of ordinary paints with a spray or brush, or otherwise. A still further object of the invention is the provision of a coating material having the char- 5 acteristics described hereinafterwhich may be applied to metal surfaces without the necessity of brightening or deoxidizing the surfaces.

A further object is to provide a coating material of relatively inexpensive ingredients which is adapted, through substitution of its specific components, to produce a coating of any desired nonnoble, non-ferrous metal.

Further objects and advantages of the invention will be made apparent in the following speciflcation, wherein it is described in greater detail.

A further object is to provide a coating material of metal-like characteristics which may be applied to produce a surface which is unaffected by moisture and unaffected even by the solvents used in the application of the material itself so 5 that it is as highly resistant to any solvent as the metal itself which is used in the manufacture of the coating material.

The invention, broadly stated, comprises the use of a metal dust mixed with a solution of a compound which, during evaporation, will result in the formation by chemical action of insoluble inorganic oxygen compounds to effect the binding together of the metal dust particles to produce a strongly cohering and adhering coating substance having many characteristics of the pure metal, itself.

In practising the invention, the metal dust, which may have been reduced to fine particles by grinding or any other suitable process, is mixed 20 with a solution, preferably aqueous or alcohol, of a salt as hereinafter described. The mixture is brought to a consistency suitable for application by brush or spray to the surface to be coated, and applied thereto in a thin film.- Upon. drying of the coating by evaporation of liquid therefrom, the oxygen in the solution and from the air combines with its soluble ingredients and forms insoluble reaction products of oxygen com pounds, surrounding and binding together the particles thereof and, at the same time, effecting a tenacious adherence of the resulting metallike mass to the surface to which it has been applied. The result is a coating having the appearance and characteristics of a solid film of the metal of which the dust is made.

It is an important feature of this invention that the quality and effectiveness of the coating does not depend on the characteristics of the surface being coated; that is to say, it may be applied effectively to surfaces of concrete, glass, wood, or cloth, and various other surfaces, painted or unpainted, as well as to the surface of any metal.

In its application to metal, the surface of the metal need not be first brightened, as is demon strated by the fact that my coating has been applied directly to the surface of rusty iron with perfect satisfaction. This is, of course, a great advantage as it permits the coating of large and complex structures which can not, as a practical matter, be treated by such methods as electroplating and fusing. I

My invention also makes possible the provision of a uniform metal-like coating on structures embodying several unlike materials, such as iron,-

concrete and wood, all such materials being highly receptive to the application of the coating.

In the following description certain specific examples are cited to illustrate the manner of practising the invention. These examples, however,.are to be taken as illustrative only, and not as limiting the invention to the particular ingredients specified or steps of the method recited.

The coating may be made with the dust of practically any non-noble, non-ferrous metal, such, for example, as zinc, tin, lead, magnesium, copper, cadmium, bismuth, aluminum, antimony and arsenic, and will, of course, upon being applied as specified herein, provide a surface having characteristics of the particular metal used. Various alloys or mixtures of these metals may also be used.

The soluble compounds which are used in an aqueous or alcohol solution to react with the surfaces of the metal dust to cause it to be readily receptive to oxidation and to the formation of the insoluble reaction products of oxygen compounds by which the particles are bound together, are, chosen from the soluble salts containing the ion or ions of halogens, sulphur, boron, carbonates,'citrates, tartrates, acetates, formates, oxylates, cyanide, nitrates and phosphorus, in salts of sodium, potassium, ammonium, magnesium, calcium, barium, strontium, aluminum, cadmium, bismuth, manganese, arsenic, antimony, mercury, tungsten, chromium, nickel, zinc, lead, tin, iron, copper, zirconium, molybdenum and titanium.

I have made over 5,000 different coatings using the metal dusts specified with solutions of the soluble salts specified containing the ions as specified. I find that any salt that has a tendency to cause the surfaces of a metal dust to be receptive to oxidation when in contact with water or alcohol and air, and especially when in the form of a thin coating exposed to the atmosphere, will result in binding the metal particles together when such reaction takes place. The reaction is either fast or slow depending on the character of the metal dust, the fineness of its particles and the character of the solution of a salt.

I prefer the easily obtainable salts that are comparatively cheap and can be obtained in the technical grades, such, for example, as the chlorides and chlorates, sulphides and sulphates, nitrates, acetates, carbonates, citrates, tartrates, phosphates and borates of ammonium, sodium, potassium, calcium, barium, antimony, nickel, aluminum, cadmium, zinc, iron, copper, chromium, cobalt, lead and tin; the sodium and potassium salts of lead, tin and antimony; the chloride of arsenic and its acids; the chlorides, chlorates, acetates, sulphates and nitrates of magnesium and manganese; and the chlorides and nitrates of mercury.

I have mixed with a mixture of metal dust and a solution of a salt, for the purposes oi color, texture and other effects, the non-caustic oxides and hydroxides of chromium, arsenic, antimony, boron, silicon, aluminum, iron, lead, zinc, tin, copper, nickel, bismuth, cadmium, magnesium, manganese, titanium, zirconium and molybdenum; the arsenates, arsenites, phosphides, sulphides, carbonates, and silicates of chromium. antimony, aluminum, iron, lead, zinc, tin, copper, nickel, cadmium, magnesium and manganese; the fluosilicates of sodium, potassium, ammonium, magnesium and zinc magnesium; and carbon, silicon, boron, sulphur, selenium, thallium, tanta- Example 1 Parts Zinc dust -I 100 15% to 20% of an aqueous solution of sodium chlori 25 These ingredients, in the proportions given, are mixed and form a liquid of a consistency that may be applied to a surface by spraying or brushing. The water is evaporated from the coating after it has been applied, while the coating is kept physically undisturbed until the reaction between the sodium chloride solution and the surfaces of the zinc dust and the oxygen in the solution and in the air form insoluble reaction prodnets of oxygen compounds.

The step of evaporation will, under normal circumstances, take place at the proper rate to effect the necessary chemical reaction in a suitable manner. This step may, however, be controlled if necessary. For example, when evaporation is too slow, as in humid weather, moderate heat may be applied, as by blowing warm or dry air over the surface; or, if the evaporation has a tendency to take place too rapidly because of warm or dry weather, the coating may be bathed with Water or alcohol to retard the action.

By keeping the coating physically undisturbed it is meant that rubbing or otherwise agitating the coating while it is hardening on the surface is not only unnecessary but undesirable. Furthermore, the heat generated by the chemical reaction or from any other source should be controlled at least to the extent that it will not cause turbulence of the coating in its fluid state and prevent its hardening to a smooth, even surface.

Earample 2 Parts Zinc dust 100 20% alcoholic solution of zinc chloride 50-75 Arsenic trioxide 2 These ingredients are mixed and applied as described in connection with Example 1. This formula is particularly adapted for the production of coatings to be immersed in water, and the purpose of the arsenic trioxide is to produce an antifouling compound or to prevent the adherence of marine growth to the surface of the coating.

' Zinc chloride-20% solution in methanol plus 1% of glycerin 50 Arsenic trioxide l5 Arsenic sulphide (red arsenic) 7 Titanium oxide 4 Chloride of nickel 2 Chloride of chromium 2 The above ingredients are mixed and applied in the manner described in connection with Example 1. More of the methanol ormore of the 20% solution of zinc chloride and methanol may with water or a solution of one of the soluble salts specified herein to prepare the same for any suitable method of plating, such as electric deposition, to produce the desired effect. It is also possible to apply mercury to form an amalgam with the surface of the coating applied in the manner of the present invention.

The reactions which take place to produce the oxidation which effects hardening of the coating may be controlled so that they are retarded or prevented within the mixture to give an extended time for its application to a surface. This is desirable as a convenience to facilitate the handling and the application of the fluid and so that it may be applied before other reactions take place in the container. This factor is controlled by the proportioning of the soluble salt in its solvent, and also by the proportion of the salt solution mixed with the metal dust. As is evidenced in the examples given above, when using a zinc salt dissolved in water or alcohol, I find that a 15% to 20% solution of the salt is suitable.

When using an aqueous solution of a salt, as for example sodium chloride, I mix 25 cc. of a 15% to'20% aqueous solution of the sodium chloride with about 100 grams of zinc dust. When using an alcohol solution of a salt, for example zinc chloride, I mix 50 or 75 c. c. of a 20% alcohol solution of zinc chloride with about 100 grams of zinc dust. These proportions give ample time for application; a controlling agent or compound may be used if a longer time is desired for application after mixing. However, when using an alcohol solution of, say, 15% zinc chloride and nickel chloride, 100 c. c. of such solution being mixed with 100 to 200 grams of zinc dust, a controlling compound is desirable to extend the time for application. Any. suitable controlling agent may be added; for example, glycerin in any amount, preferably in small amounts, say 1% or less of the volume of the salt solution, retards the reaction of the nickel salt in the completed mixture, giving an extended time aftermixing for its application.

Mixtures in which the soluble alkali salts and alkaline salts are incorporated in the proportions suggested in water solutions havethe advantage of cheapness, and where the time of evaporation and completion of the hardening is not considered of importance, these water solutions may be used. Where rapid evaporation and hardening is desired, as, for example, in cases where a surface is to be coated two or more times, or where the coating is to be immersed in water Within a short time after hardening, the mixtures including salts soluble in alcohol are preferred, although more than one coating may be applied with the water mixtures if sufficient time is given for hardening of the first coating before the second coating is applied.

I have found that the dust of non-ferrous metals, when used in accordance with thispresent invention, results in the prevention of corrosion of the iron or steel surfaces to which it is applied, even though the surface is more or less rusty when the coating is applied.

The soluble ingredients contained in any of the several mixtures of my invention maybe disapplication. Likewise all of the solids of. the

mixture may be first mixed and the solvents there.-

after added to the mixture before application.

As an alternative to the methods of applying the coating as described above, the metal dust may be mixed with water or a weak solution of an adhesive and applied to the surface to be coated, and thereafter washed or painted with an appropriate solution of a salt to produce the reaction which forms the coating of 'my invention, oragain the metal dust may be mixed with a solution of caustic alkali such as sodium or p0- tassium hydroxide applied to the surface and thereafter washed with an acid to produce a salt for the purpose ,of the reaction. While these methods of applying the'dust to the surface first 'and thereafter applying the reaction agent are desirable for some purposes, the other method hereinbefore described, wherein the dust is first mixed with a solution of the salt and then painted on the surface, constitutes the preferred form of my invention.

From the foregoing description it will be apparent that I have provided a metal-like coating material and method of applying the same that are adaptable to forming coatings of many kinds of metals and the application of which is not limited to any particular kind of surface or to the preparation of the surface before it is applied; and that the coating of my invention has the characteristics of the metal contained in it and yet may be applied as easily and as readily as any ordinary paint.

While I have, in the description of my invention, specified certain amounts and proportions and other details, it is to be understood that these may be varied to a great extent within the spirit of the invention, the scope of which is not limited by these details but is defined in the appended claims.

Having thus described my invention, what I claim and desire to secure by Letters Patent is- 1. The process of coating a surface which comprises applying thereto a mixture consisting of zinc dust, zinc chloride solution in an alcohol, arsenic trioxide, red arsenic, titanium oxide, chloride of nickel and chloride of chromium.

2. The process of producing a metal-like coating comprising metal particles bound by insoluble inorganic oxygen compounds which comprise mixing zinc dust with a solution of inorganic salts in such proportion as to be capable of reacting with the zinc and oxygen to form the said compounds on a surface, coating the mixture onto the surface, and then exposing the coated surface to the air while maintaining the coated surface under conditions favorable to the formation of the aforementioned oxygen compounds until the coating is formed.

3. The process of producing a metal-like coating comprising metal particles bound by insoluble inorganic oxygen compounds which comprise mixing zinc dust with an alcohol and water solution of inorganic salts in such proportionas to the coated surface under conditions favorable to the formation of the aforementioned oxygen compounds until the coating is formed.

4. The process of producing a metal-like coating comprising metal particles bound by insoluble inorganic oxygen compounds which comprise mixing zinc dust and a solution of sodium chloride in such proportion as to be capable of uble.inorganic oxygen compounds which com-V prise mixing zinc dust and a solution of zinc chloride in such proportion as to be capable of reacting with the zinc and oxygen to form the said compounds on a surface, coating the mixture onto the surface, and then exposing the coated surface to the air while maintaining the coated surface under conditions favorable to the formation of the aforementioned oxygen compounds until the coating is formed.

6. The process of producing a metal-like coating comprising metal particles bound by insoluble inorganic oxygen compounds which comprise mixing zinc dust with an alcoholsolution of inorganic salts in such proportion as to be capable of reacting with the zinc and oxygen to form the said compounds on a surface, said solution containing a small proportion of glycerine, coating the mixture onto the surface, and then exposing the coated surface to the air while maintaining the coated surface under conditions favorable to the formation of the aforementioned oxygen compounds until the coating is formed.

GEORGE S. SMITH.