US1729766A - Cleaning of metal surfaces - Google Patents

Description

Gil

Patented Oct. 1, 1929 PATENT OFFICE CLARENCE F. DINLEY, OI DETROIT, MICHIGAN CLEANING OF METAL SURFACES No Drawing. Application filed August 14, 1926, Serial No. 129,278. Renewed December 7, 1927. Y

My invention relates to the cleaning of metal surfaces, particularly of fabricated steel. and involves a new cleaning agent or compound as well as a new cleaning method or technique. -The invention is especially useful in preparing the surfaces of metal vehicle bodies for painting, enamelling, orthe like, and I have hereinafter described and explained it with special reference to this use. Surfaces cleaned in accordance with my invention are left in a high state of cleanliness, free from all deleterious foreign substances such as oil, grease, and the like, as well as from rust (even in the incipient stage repre-.

sented by so-called yellow bloom) and from rust stimulants, and in excellent condition for the immediate, direct application of lacquer or the like. Hence the employment of my invent-ion maks it practicable to dispense with oil primer and other under coats between the metal and the lacquer; and this, in view of the fact that my process can be carried out very quickly and conveniently, greatly reduces the time consumed from the stage where the cleaning is begun. until the lacquer is applied. The invention materially reduces the cost of cleaning, and is free from danger or injury to the workmen engaged in the treatment,such as is involved in the use of the sand blast for such purposes.

How these and other advantages can be r ialized through my invention will be apparentfrom my description hereinafter of selected and preferred modes of practicing it. In practice, I apply to the metal surface to be cleaned a. coating of a composition such as hereinafter described, in a liquid state. While this can be done with a brush, or in any other convenient way, I generally prefor to employ a spray gun for the. purpose, using the'ordinary spray gun equipment, including a pressure tank equipped with an agitator. with an air pressure of about 20*30 lbs. A little while after the application of this coating, as soon as it has had opportunity to act on the foreign matter to be removed and to penetrate the pores of the me tallic surface, I-dry it by subjecting the coat ed article. to a moderate degree of heat for a short time. This not only dries the coating in preparation for removal, but also, preferably, produces other effects: particularly, it neutralizes any excess of the rust-removing agency of the composition, so that the same cannot subsequently attack the metal; and it causes the coating to become-friable and flaky, and, in large measure, to peel off of itself. This peeling effect is largely due to the reaction of the ingredients rapidly brought about by the heat,-though naturally favored by the drying of the coatin ()r,

if time is not so important, I obtain the same result by exposure of the liquid to room temperatures for say from one to three hours. Any residue of the coating is removed mechanically, as with sand paper, steel wool, or long rotary fibre brushes. The cleaned article is then preferably given an. alcohol bath and wiped dry, which leaves it ready for its protective coating or subsequent finishing, as lacquer, enamel, or-paint.

Aside from its cleaning action, my composition such as referred to above is a very effective preservative against rust. In some cases, therefore, it may be applied for this purpose and left on the article indefinitely; the ingredients being varied somewhat so as to prevent its peeling off of itself as above described. Subsequently, when the time 7 comes for lacquering or enamelling the ar-- ticle, this preservative coating may be removed by an application of the composition in its self-peeling form.

The composition which I prefer to employ comprises rust and oil removers or solvents, in combination with finely divided or powdered substances which act as a vehicle to give the liquid composition body and weight it to prevent it from sagging" when applied to the surface to be cleaned; re-act with the rust remover, as above described, to eliminate any excess thereof; and,

when present in suflicient quantity, render the dry coating highly friable, flaking, or self-peeling.

For direct and. immediate cleaning, where it is desired to have the dried coating flake and peel off spontaneously, I may employ the following ingredients in substantially the proportions indicated:

Ingredient. Amount Function Pound: Water 229 Ortho-phosphoricacid (75%). 105 Rust remqvlng and cleans- Ethyl-methyl-ketone 67 Grease solvent. Raw sienna 135 a Vehicle, etc., reacting with phos horic acid. Powdered amorphous ab- Cush nning and flaking sorptive carbon willow agent;absotbent;coloriug; charcoaL 5 etc.

Lampb eolL In cases where the composition is to be applied and left on the metal as a preservative against rust, I may employ the ingredicuts in the following proportions:

Amount Ingredient Function Pounds Water 229 Ortho-phosphoric acid(75%). 120 Rust remotving and cleansg agen Ethyl-methyl-ketone 81 Grew: solvent. Raw sienna 135 Vehicle, etc., reacting with phosphoric acid. Powdered amorphous ab- Cushioning agent; absorsorptive carbon, willow bent; coloring; etc.

charcoaL", 48

ferrous metal: e. g., selenic, oxalic, acetic,

tartaric, and citric acids have this capacity. Inlieu of the ethyl-methyl-ketone as a remover or solvent for oils and grease, I may use any organic solvent of such substance that is miscible with water, such as any of the alcohols, ketones, esters, etc, which posmove the grease by even though in quite an impure state. The

-' paints), any metallic oxide that is commersess such capacity. Necessarily the oil solvent used for this purpose must e compatible with the rust-removin agent. I have followed colloquial usage in referring to the oil and grease remover as a solvent, without strict regard as to whether suchagents redisplacement or by solution in the strict sense.

, In lieu ofthe sienna (which is an earth containing iron oxides) I may employ as a vehicle to weight and give body, etc., to the liquid composition .(like zinc or lead in cially available in sufiicient quantity and at sufficiently low cost, and possemes the prop city of reacting with the rust-removing acid,as for example, the iron oxides, such as F8 0,, and manganese oxides, or both,-

point to be observed with reference to this ingredient is that while it is to react with the acid, it must not do so at too low a tem-' perature, but only at the atmospheric (or higher) temperaturds reached in the drying; since otherwise it would convert all of the phosphoric acid before the latter had an opportunity to act on the rust. Sienna, for

'igpurities.

The carbon also absorbs the products resulting from the. action of the solvents and acids on the impurities to be removed, as well as the impurities themselves. It also acts to prevent the sienna from 'cohering and adhering too well, and thus contributes 'as a cushion to give the composition its friable, self-peeling character: without the sienna, on the .other hand, the coating would remain pasty and would not peel. 4 The reaction of the sienna with the acid, indeed, tends tocause peeling. As a pigment, also, the charcoal colors the sprayed coating of the composition black, so that any bare spots of uncovered metal are at once apparent.

In the routine of automobile body manufacture, the bodies are brought to the cleaning line from the assembly line. In cases where a considerable interval exists between these processes, the preservative form of my composition describedabove may be brushed on as the bodies leave the assembly line. It quickly forms a hard, black coating which prevents any rusting and serves as a seal for an indefinite period and remains in place I notwithstanding the subsequent application of my composition next to be described.

Whether this preservative has been used .or not in the assembly line, the procedurev at the cleaning line is the same: theselfflaking form of my composition is sprayed on the bodies as above described. Owing to the influence of the finely divided matter in the composition, the sprayed liquid coating shows no tendency to sag. After the spraying is completed, a period of at leastten minutes should elapse before the body enters a drying oven, to permit rapid action of the cleaning agent-in the wet state and penetration of the minute pores of'the metallic surface. At the end of this ten minute interval, the body should be placed in the usual oven, heated to a temperature of 150 200 F., and allowed to remain there for at least ten minutes. The type of oven used for pyroxilin enamels (consisting of a composition board enclosure heated by steam coils) is ve satisfactory.

Un er the heat of the oven, the action of the-cleaning ingredient is stimulated for a shortperiod, before the drying is actually completed, and the excess of rust remover is also neutralized. As the cleaner dries, the

flaking influence of the charcoal makes itself felt. If the film sprayed'on is too thin, this labor saving action is impeded: the thicker the film, the more readily the friable action occurs. The film both expands and contracts inlthe drying process; i. e., where the oil and grease are absorbed, their addition expands the dr ing film, while where solids such as rust, t ux etc. are picked up, the film shrinks. 'VVhere the grease on the body is thick, the cleaner film rises in a bubble and finally drops off. Where the body is very clean, or only contaminated by soldering flux, the cleaner shrinks and curls up, and then drops off. As such portions of the cleaner drop off, they carry with them all the dirt, grease, flux etc., and leave an absolutely clean surface, entirely free from powdery residue. Usually, about of the film or coating drops off in the progress through the oven and out to the next station, where the residue is removed.

The removal of the small patches of adhering film which remain after the body leaves the oven is not a tedious operation, as the flaky character of the film faciltates the cleaning out of corners and the like. If any of the cleaner remains under the edges of beads, etc., no damage or disadvantage can arise therefrom, inasmuch as the heat of the drying oven brings about neutralization of the rust-remover by the sienna or the like.

After passing through the treatment, the metal has a dull silver or satin finish, such as associated with etching. The etching action of the phosphoric acid in the cleaner is less energetic, however, than that of the soldering acids employed in the mauufzucture of bodies: accordingly, the clean body shows bright streaks where the soldering acid has been, surrounded by a satin surface,imlieating complete removal and neutralization of all acid. The slightly etched condition of the metal surface affords a good base for the direct application and adherence of primer, or lacquer, or other finish.

The alcohol bath leaves the body very clean, with a neutral surface ready for the lacquer or other final operations. Such a bath ofi'ers advantages over the usual hot water or steam bath heretofore used in such cases. First, the boiling water or steam may get into the inside of composite bodies and all'ect the wood frame. Second, no matter how thoroughly the body may be cleaned, discoloration always follows the hot water or steam bath: i. e. in the boiling or steaming bath the metal acquires the characteristic yellow bloom so well known to finishers, which in the last analysis is incipient rust or oxide of iron. Its presence necessitates the use of oil primer and under coats to cover the metal incipiently rusted over the entire body, and these must be thoroughly oxidized breaks in the water'film on its surface will be observed,such breaks being a sure indication of grease, even though invisible to the naked eye before testin On the other hand, panels cleaned. by my process are entirely free from breaks in the waterfilm when subjected to such a test. Moreover, panels cleaned in accordance with my invention and coated with transparent varnish withstand a fadeometer test must longer than those cleaned by present methods.

Advantages which follow from the use of my process, as thus described, are great permanency of the finish subserpiently applied and ease of application, the materials not being injurious to the hands of those applying it. If acleanser of this character is liquid, and if small quantities of it remain concealed in crevices until after the finishing of the surface, the cleanser ultimately works out and mars'the surface, whereas my material,- it thus lOL'O-lVOtl into crevices, merely dries and remains harmless.

Having thus described my invention, I claim:

1. A coating and drying composition for removing foreign substz'rnces such as rust and oil from metal surfaces preparatory to painting; comprising compatible.rust and oil solvents in combination with a finely divided vehicle and a finely divided absorptive agent cooperating with other ingredients to render the composition friable and self-peeling when dried.

2. A coating and drying composition for removing foreign substancessuch as rust, rust stimulants, and oil from metal surfaces preparatory to painting; comprising compatible solvents for the said substances in combination with a finely divided vehicle and powdered absorptive, amorphous carbon.

3. A coating and drying composition for removing foreign substances such as rust and oil from metal surfaces preparatory to painting; comprising compatible rust and oil solvents in combination with a finely divided vehicle substantially inert at ordinary temperatures, but reacting with the rust solvent under moderate heat to cause the composition to peel off when dried.

4:. A coating and drying-(-omposition for removing foreign substances such as rust and oil from metal surfaces preparatory to painting; comprising compatible rust and oil solvents in combination with a finely divided vehicle substantially inert at ordinary temperatures, but reacting with the rust solpainting;

vent under moderate heat, and a finely dividedv absorptive agent.

5. A coating and drying composition for removin foreign substances such as rust and oil frommetal surfaces pre aratory to comprising compatib e rust and oil solvents in combination with a finely divided vehicle substantially inert at ordinary temperatures, but reacting with the rust solvent under moderate heat, and a finely divided absorptive agent cooperating with said vehicle to render the composition friable and flaking when dried.

6. A coating and drying composition for removing foreign substances such as rust and oil from metal surfaces preparatory to painting; comprising an oil solvent, sienna, and a rust-solvent acid compatible with the oil solvent and reacting with the sienna under moderate heat to cause the composition to peel off when dried.

7. A coating and drying-composition for removin" foreign substances such as rust and oil from metal surfaces preparatory to painting; comprising an oil solvent,.sienna, a finely divided absorptive agent cooperating with the sienna to'render the composition friable and fialEing when dried, and a rustsolvent acid compatible with the oil solvent and reacting with the sienna under moderate heat.

8. A coating and drying composition for removing foreign substances such as rust and oil from metal surfaces preparatory to painting; comprising an oil solvent, sienna,

' powdered. amorphous, absorbent carbon, and

a rust-solvent acid compatible with the oil solvent and reacting -with the sienna under moderate heat.

9. A method of removing foreign substances such as rust and oil from metal surfaces preparatory to painting, which method comprises coating the surfaces with a liquid composition comprising rust and oil solvents in. connection with a finely divided vehicle substantially inert at ordinarv temperatures, but reactingwith the rust solvent under moderate heat, and a finely divided absorptive agent cooperating with said vehicle to render the dried coating friable and flaking; allowing the wet coating to act on the foreign substances; and heating and drying the coating under a heat sufficient to cause reaction between said vehicle and said rust solvent.

10. A method of removing foreign substances such as rust and oil from metal surfaces preparatory to painting, which method comprises coating the surfaces with a liquid composition comprising an oil solvent, sienna, powdered amorphous, absorbent carbon, anda rust-solvent acid reacting with the sienna under moderate heat; allowing the wet coating to act on the foreign substances;

(:5 and heating and drying the coating under a heat suflicient to cause reaction between said vehicle and said rust solvent.

11. A method of removing foreign substances such as rust and oil from metal surfaces preparatory to painting, which method comprises coating the su'rfac es with a liquid composition comprising compatible rust and oil solvents in combination with a finely divided vehicle substantially inert at ordinary temperatures, but reacting with the rust solvent under moderate heat; allowing the wet coating to act on the foreign substances;

and heating and drying the coating under,

a heat suflicient to cause reaction between said vehicle and said rust solvent.

12. A method of removing foreign substances such as rust and oil from metal surfaces preparatory to painting, which method comprises coating the surfaces with a liquid composition comprising an oil solvent, sienna, and a rust-solvent acid compatible with the oil solvent and reacting with the sienna under moderate heat; allowing the wet coating to act on the foreign substances; and heating and drying the coating under a heat sufiicient to cause reaction between the sienna and said rust solvent.

In testimony whereof, I have hereunto signed my name at Detroit, Michigan, this 9th day of August, 1926.

CLARENCE F. DINLEY.