US2045932A - Coating composition - Google Patents

Description

Patented June 30, 1936 PATENT OFFICE 2,045,932 COATING COMPOSITION Percival Thee], Janettown, Pa.

No Drawing. Application September 4, 1930, Serial No. 479,809

10 Claims. (CI. 91-70)" This invention relates to a method for applying compositions designed to protect against corrosion and to the compositions themselves. It is particularly directed to the application of compositions to iron, steel and other surfaces apt to corrode rapidly at high temperatures, such as when used on locomotive fronts and blast furnace piping and for similar purposes.

So far as I am aware, there has not been devised a paint capable of withstanding corrosion for long intervals when used on locomotive fronts, blast furnace pipes and like structuresor under similar conditions. The principal qualities desired of such a coating arecheapness of com- 1 ponents and ease of combining them, ease and smoothness of application, formation of a continuous film of protecting material and maintenance of the continuous film through a wide temperature range, with suflicient cohesion to resist contact of air and other weathering agencies with the surface to be protected.

The principal object of my invention is accordingly to provide an improved process and composition for such purposes. Further objects, features and advantages will more clearly appear 1 from the detailed description given below wherein the preferred embodiment of my improvements is specifically described.

In the composition which I have discovered, I employ 1) a binder such as tar which may be readily spread to produce a coating and at the same time will hold another component or com-' ponents of the coating in place, and (2) a fusible material to be mixed with the binder and having a fusion temperature somewhere near the point that the binder decomposes or breaks up on heating, capable of forming a protective film when fused. With these two ingredients I usually prefer to employ a vehicle to carry the binder and fusible material and to aid in the application of the composition to the surface to be protected.

To the composition I also add a suitable pigment or pigments to change the color of the coating,

but these pigments may ofv course be omitted where not so required.

As a binder and film-forming material, I may use tars or similar materials which substantially retain their film-forming and binding characteristics up to elevated temperatures and a fluxing material which I shall designate as a frlt in the ,specification hereafter and in the claims. I use a fusible material having a relatively low melting point and preferably having a melting point in the neighborhood of the temperature at which the binder decomposes and begins to lose its protective qualities. I preferan inorganic material such as afusion product of litharge and boric acid for the frit. The decomposition points of the tars or other binders and of the frit may be varied considerably according to the use to which 5 the paint is to be put. It is important that the protective film be maintained throughout the range of heat and under the other conditions to which the paint is subjected in use.

I believe that the chemical character of the frit 10 chosen should be such as to superficially attach to the scale or surface of the iron or steel and form therewith in the presence of the organic binder and heat a sort of metallic boro ferrite or other mixed ferrite which is almost integral with 15 the iron or steel and adapted to wet the surfaces thereof and spread into a thin glaze thereon and unite therewith. The ingredients including the binder and frit should be selected with this point in view. The vehicle selected may be such as 20 merely dissolves or thins the binder, or may have the property of forming by itself a film as well as to dissolve or disperse the binder. On the other hand, of course, the binder may itself require no thinning but may be used as such with the frit 25 to form a satisfactory paint for certainfpurposes. As a vehicle I prefer 'to employ pine oil or a mixture of pine oil and turpentine together with a small amount of alcohol and mineral oil.

In carrying out my invention I prefer to use 30 a coal tar which is aproduct of the Barrett Company having a specific gravity of about 1.17 at ordinary temperature, which on being heated cracks or decomposes at about 340-400 C. I have selected this tar as giving the desired results when 35 used in the formula given below, but it will be understood that this tar is one of a number of like compositions which may be used and it is important to remember that the tar or binder selected will vary with the conditions under which 40 the paint isto be employed and in'accordance' with the melting point of the frit used.

- For the .frit I prefer to employ a material containing a fusion product of litharge and boric acid. 45

Frit A.-For a frit having a melting point of about 360-370" C. and suitable for the manufacture of an aluminum paint, I mix:-

4516 parts by weight of litharge,

82 parts by weight of boric acid.

These two ingredients in powder form are mixed thoroughly and then fused in an electric cru cible furnace at-a temperature upward or 900 C. When fused in a crucible of, zirconiml prefer to add 25 parts by weight-of borax before-Tplac- .the zirconia of the and boric acid as given above in A, Before fusion,

however, there is added parts by weight of black oxide of cobalt. The fusion point-of this frit is about 360C.

Frit (L-For use in black paints for extreme heats where the metal surface to be protected reaches a temperature where it glows with the heat, I make up the frit as foliows:-

446 parts by weightof' litharge,

62.5 parts by weight of boric acid,

30 parts by weight of silica,

20 parts by weight of black oxide of cobalt.

The ingredients in powder form are mixed thoroughly and then fused in an electric crucible furnace as above. The fusedmass is then poured into water for pulverization and then ground in a mill. The ground mass has a fusion'point of about 410-420 C.

Instead of the frits melting at. 360-420 C. mentioned above as Frits A, B and C, Ihave made frits with different melting points as follows for example:---

'Frit D.--A frit made with 190 parts of litharge to 240 parts boric acidwhen fused together will produce a product having a melting point of On the other hand I make a higher melting point frit, for example as follows:

Frit E.-446 parts of lithage,

168 parts of boric acid,

40 parts of silica, 20 parts of black cobalt oxide,

are melted and a frit having a melting point of 480 C. is obtained. In this formula the addition of silica andcobalt oxide somewhat reduces the fusibility of the resulting mass. I

titles as desired:-- a,

For green chromic sesquioxide For r Ferric oxide I'br gray Stannous oxide For blue Cobalt oxide orcopper oxide The following are formulae of paints combining preferred binders and frits for aluminum finish and black paints:

Aluminum finish paint-Thecomposition of this paint is preferably as follo 10 parts by weight of coal tar. about 340-400 C.,

Cracking point 15 parts by weight of m A (fuses about sen 8.6 parts by weight pine oil or mixture of pine oil and turpentine equal parts,

0.5 part by weight of alcohol denatured, 0.5 part-by weight of mineral oil B. P. 360 C. To this is added just before painting 10% by weight of powdered aluminum.

replaced by aluminum paint and If aluminum is added when the other ingredients are mixed it will not flake properly when painted after standing 24 to 48 hours and the result will be an aluminum gray.

Black paint.- -The composition of this paint 5 is as follows:-

12 pounds Frit B.

0 pounds Frit C,

1 pound copper oxide black,

0.5 pound black cobalt oxide, 10 pounds of coal tar. Decomposition point about 340-.400 C.,

1 pint pine oil,

1 pint turpentine,

0.5 pint alcohol, denatured,

1.5 pints of mineral oil. I The two frits, and the copper and cobalt oxides, in the proportions stated above are mixed and added while stirring to the other ingredients.

The pine oil mentioned in these formulae is of the hydrocarbon type and contains fractions around -170 C., although the major proportiondistills at about C. The turpentine is steam distilled. It is preferred but may be a corresponding quantity of benzol. The alcohol employed is ordinary denatured alcohol, denatured with wood alcohol and benzine (No. -l formula). The mineral oil employed is the type made by Atlantic Refining Company and distilling at about 400 C.

These paints are appliedin the ordinary manner with a brush or spray and when applied resist corrosion resulting from various agencies including weathering and heating through wide temperature ranges. They are preferably applied while the metal to be protected is at a low temperature.

Paints including the above compositions have been employed for the protection of incinerator stacks, producer stacks, smoke boxes on locomotives, bleeder pipes of blast furnaces, for cement kilns and other similar uses. Incinerator stacks often become so hot that'they glow with a dull light at night but the black paint formula given above has been satisfactorily employed to give a protective coating on these stacks. I believe that the temperature of these stacks when glowing is approximately 500 C.

. I have obtainedsimilarly good results for the same composition on producer stacks, the bottom of which I estimate to be at'about 450 C. In the bleeder pipes of blast furnaces the heat to which these pipes are subjected leads to a complete destruction by corrosion of the pipes and the consequent loosening of the fire clay lining. These pipes when coated with the above mentioned formulae have been found to resist this corrosion with consequent saving in the expense of replacement not only of the metal pipe itself, but also of the lining. On the forward end of locomotives, the practice is to use a graphite coating which requires replacing in about 10 days and affords imperfect protection to corrosion of the metal beneath it. An ber of locomotives which have been painted with my composition 65 have been running for 5 to '1 months without replacement of the paint. I have found that the other compositions made according to my invention behave in a similarly excellent manner.

when applied to the surfaces of locomotives, incinerator stacks, bleeder pipes, etc. mentioned above, thes'paint compositions give a substantially uniform film over the metal surface and as long as the temperatures are relatively low and While I have described my improvements in detail and with respect to certain preferred forms, I do not desire to be limited to such details or forms since, as will be noticed by those skilled in the art, after understanding my invention, many changes and modifications may be made and the invention embodied in widely different forms without departing from the spirit and scope thereof in its broader aspects, and I desire to cover all modifications, forms and improvements coming within the scope of any one or more of the appended claims.

What I claim as new and desire to secure by Letters Patent is:

1. The process of protecting surfaces of iron and steel subjected to wide variations of tem perature from atmospheric corrosion and rusting which comprises applying thereto in the form of a paint a binder substantially composed of decomposable organic material forming a hard,

substantially water-insoluble skin which is weather resistant at relatively low temperatures up to about 400 C. but which will burn oil! or otherwise cease to protect it at high temperatures, and a fusible frit which whenit fuses will give a water-insoluble surface glaze to the metal to protect it at both low and high temperatures, and subjecting'the metal to a high temperature to remove at least part of the binder and to cause some melting of the frit, the decomposition point of the binder and the melting point of the frit overlapping to provide a' composition for protecting the metal at temperatures ranging from ordinary temperatures to red heat and above.

2. A process according to claim 1 in which and a fusible material which when it fuses will the metal the decomposition of the binder and the melting point of the fusible material overlapping to give a paint composition which will protect metal at temperatures ranging from ordinary temperatures to red-heat and above.

4. A paint composition according to claim 3 in which the binder is a weather-resistant waterinsoluble organic material having a decomposing temperature of about 340400 C. and in which give a water-insoluble surface glaze to protect S the fusible material is a water-insoluble-metal t borate having a melting point a little below the decomposition point of the organicmaterial the composition serving to protect metal orsimilar substance in a range of temperature from ordinary temperature to red heat or above.

5. A paint ,composition according to claim 3 in which thebinder is a tar, and the fusible material is a water-insoluble metallic borate.

6. A paint composition according to claim 3 in which a volatile organic solvent is employed as a vehicle.

7. A metallic structure subjected from time to time to high temperatures and variations in temperatures and to corrosive agents coated with a hard, substantially water-insoluble skin of an organic binder composed substantially of decomposable organic material weather resistant at relatively low temperatures up to about 400 C., but which will decompose at high temperatures, and a fusible material which when it fuses will give a water-insoluble surface glaze to protect the metal at low and high temperatures the decomposition temperature of the binder and the 35 fusion point of the fusible material overlapping to give a coatingfor protecting the metal at temperatures ranging from ordinary temperature to red heat and above.

8. A paint composition comprising coal tar, leadborate and a vehicle containing turpentine, alcohol and an oil.

9. A paint composition according to claim 8 I in which the coal tar has a decomposition range of about 340-400" C. and the'lead borate has melting range of 360-420" C.

10. A paint composition for metallic structures having a tar binder with a decomposition range of about 340-400 degrees C. and lead borate having a melting range of about 315-420 degrees C., the paint being adapted to protect metal structures at temperatures ranging from ordinary temperatures to red heat and above.

PERCIVAL THEEL.