US1729767A - Preparation for removing foreign substances from metal surfaces - Google Patents

Description

Patented Oct; 1, 1929 umrso STATES PATENT (me omamron r. DINLEY, or nnrnogr; mm. rnaraaa'rron iron nnnovmaroanreu ,sunsraitpas anon nearer. scar-eons ll'o Drawing. original application and February 11, 1925, Serial I'D/@538. Divided and um application filed November 30, 1927. Serial No. 236,884.

. K This invention relates to the treatment of metal surfaces, especially of fabricated steel, whereby said surfaces are freed from fore1 substancessuch as oil, grease and the li e, 6 along with rust, and all rust stimulants, and are left in a condition to receive and retain a protective coating of paint, enamel or the like. This a plication is a division of m W application Serial No. 8,538,filed Februar 11, H 1925, and is especially concerned with a material or composition for use in the treatment of metal surfaces as just set forth.

The present usual method of preparing such surfaces for painting is either y the use of a sand blast, or by treating the metal with suitable liquid acid of various kinds usually containing alcohol as an oil displacer or solvent. Sometimes the two are used in conjunction. I The sand blast method is very injurious to the workmen who apply the treatment. The liquid acid treatment involves mechanical difficulties in securing the even distribution of the reagent upon the surface to be treated. The thin liquid condition of the acid solution requires many applications to keep the metal wet during the sanding operation, and in addition to the above the acid solution penetrates all cracks and crevices from some of which it is impossible to completely remove it, and from which the acid later works out due to the action of the heat required to set the paint used. The acid which thus seeps out during the heating has a very deleterious 85 effect on the permanency of the finished protective coating. This condition exists in spite of the fact that a large excess of water is used to remove this acid. The water used for this purpose (the metal being in a fairly 40 clean condition) produces its usual effect and causes the metal to have a bronze discoloration, which is incipient rust; and while this condition may be overcome in the hands of an expert, it'is rather difiicult to eliminate this 4 discoloration in practice. 4

.My present invention involves the use of an inert aqueous paste in which are incorporated the rust and oil removing agents. This paste com osition may be sprayed or otherwise applied to the surface in a continuous layer or coating, which thus remains upon the surface, and which before drying absorbs much of the dissolved rust and grease, and which after drying clings tenaciously to any softened rust or rease remaining on the sur- 65 face, so that w on in its dry condition it is brushed or flaked oif, the complete removal of these substances from the metal surface is effected, thus calling for much less, if any, subsequent abrasion of the surface than 1n the previously described recess.

The aqueous paste ma e formed by add- 1n Water to any finely ivided inert mineral su stance, capable of producing the desired plastic mass. Various clays or similar substances may be employed, but I prefer to use cryolite, silica, alumina, powdered talc or fluor spar and the like.

As the rust-removing agent, I employ any of those acids which have'the capacity of readily dissolving, or rendering harmless to paint, the iron oxides, chlorides or iron salts liable ,to be found upon metal surfaces. Most of the mineral acids, and also oxalic, acetic, tartaric and citric acids have this 7 capacity. Phosphoric acid has long been used for this purpose. A mineral acid that forms water-soluble salts with iron may be employed singly or can be used in conjunction with organic acids capable of producing insoluble iron salts by double decomposition. For example tannic acid with sulphuric acid in the presence of iron results in the formation of insoluble iron tannate.

As a removing agent for the oil and grease which is usually found upon'the surfaces of metal, I may employ any of the alcohols, ketones or esters which possess the capacity of dissolving or displacing the oil or grease. Various aromatic hydocarbons also possessasimilar capacity.

In order that the aqueous paste may remain a homogeneous mass and maintain the finely divided material in suspension, I prefer to add a metallic salt which when preci itated by the oil solvent will produce a fioccuient coagulant having this effect. Many ferric and other metallic salts possess this quality.

' I will now describe a preferred method of preparing my material :To 250 cc. of water stance some of these materials while the rest I add 32 of til the There is then added'QOO rams of finely divided inert material, as fbr example a mixture of 125 grams of fullers earth with 75 gramsof kaolin. After this has been thoroughly stirred into the mixture there is added 250 cc. of denatured alcohol or other slmilar oil remover.

The proportions given above may be varied provided there be used a sufiicicnt amount of the reagentsto act upon the rust and grease, and provided also the materials be so pro )ortioned as to produce an aqueous paste 0 the proper consistency to permit of easy application to the surface in an even layer, whlch will not run down a vertical surface, and

grams of ferric phosphate andlicc. iosphoric acid. This is stirred un which may be readily dried by application of a moderate temperature, and which when thus dried does no adhere too tenaciously to the metal, but is flaky and friable and therefore readily removable. While the phosphoric acid in the foregoing formula has hygroscopic properties, yet it is present only in a decidedly minor proportion as compared with the finely divided material, so that the residue of it left from reaction with the rust does not prevent the paste from drying to a friable coating or deposit on the metal surface to which it is applied, nor render the coating deposit sensibly or materially hygroscopic. On the contrary, the coating remains substantially dry and friable indefinitely.

The suspending agent (ferric phosphate) keeps the composition homogeneous when first applied, and prevents it from running or sagging,notwithstanding the rather large proportion of liquid organic oil re- 'mover.

To apply this material to the surface of metal objects I prefer to employ a spray, but it may be otherwise applied, as with a brush. If there is no hurry it may be permitted to air dry, but for ordinary purposes I prefer to place the object thus coated in an oven heated to a noninjurious drying temperature, by means of which the drying may be effected in a comparatively few minutes. The heat is further serviceable in hastening the reactions, and rendering the oil more easily absorbed. When thus dried the paste which I have described will be found not tenaciously adhesive, but in a flaky condition,-quite friable and very readily removed by slight rubbing, as by steel wool.

During the drawing process the reagents have softened or dissolved the rust, oil and grease upon the surface to which they are applied, and the finely divided inert material will be found to have absorbed into its subare softened and are tenaciously adherent to the dried paste when rubbed off, so that the metal surface is left in the desired clean confbrric phosphate is fully dissolved;

dition. It may then'be slightly abraded and lightly wiped to remove dust, and is then ready for painting or other treatment.

The finely divided material erforms a combination of useful mechanica functions. It actsas the vehicle for securing the even application of the reagents to the surface of the metal and their maintenance in proper contact long enough for them to perform their function. It further acts as an absorbent taking to itself the dissolved materials which are to be removed. Further it clings with tenacity to softened, but unabsorbed articles of rust or grease, and when dry is riable and flaky, easily brushed off, carrying With it these adherent particles of foreign substances which it is desired to remove.

The finely divided substance or vehicle may be any finely divided mineral material which is not acted upon chemically by the other substances employed when mixed with them to form the paste, and is thus inert or compatible with respect to the other in redients. I have instanced a combination of fullers earth with kaolin. These substances differ in particle fineness and I find that it is advantageous to either choose or produce a material possessing different particle finenesses, as such mixtures appear to be more absorbent and tenacious than would otherwise be the case, and yet have the capacity to dry out into a friable, as distinguished from too dense and adherent a coating.

Having thus described my invention, I claim:

1. A coating and drying composition'for removing foreign substances such as rust and oil from metal surfaces preparatory to painting, the same comprising rust and oil solvents in combination with a finely divided vehicle and a metallic salt whichcooperates with the oil solvent to maintain the finely divided material in suspension.

2. A preparation as in claim 1 wherein the oil solvent is alcohol, the rust dissolving acid is phosphoric acid, and the metallic salt is ferric phosphate.

3. A coating and drying composition for removing foreign substances such as rust and oil from metal surfaces preparator to painting, the same comprising rust an oil 5. A coating and drying composition for removing foreign substances such as rust and oil from metal surfaces preparatory to painting, the same comprising rust and oil solvents in combination with finely divided material formin with the foreign substances to be remove when applied and dried on a metal surface to be cleaned, a loose, friable coating.

6. A preparation as in claim 4: wherein the finely divided material comprises inert material of difi'erent particle finenesses.

7. A preparation as in claim 4' wherein the finely divided material includes a flocculent coagulant for maintaining the rest of such material in suspension.

In testimony whereof, I have hereunto signed my name, at Philadelphia, Pennsylvania, th1s 29th da .of November 1927.

cLAimNcE F. DIiILEY.