US2756120A - Process and sheet packaging material for inhibiting corrosion - Google Patents

Description

I atent 2,75%,120 Patented July 24, 1956 fine PROCESS AND SHEET PACKAGING MATERIAL FOR INHIBITING CORROSION Robert L. Lothringer, Homewood, Ill., assignor to Sinclair Refining Company, New York, N. Y., a corporation of Maine No Drawing. Application November 12, 1952, Serial No. 320,131

6 Claims. (11. 21-25 My invention relates to corrosion inhibition and more particularly to vapor phase corrosion inhibition in which the inhibiting agent vaporizes to deposit a protective coating on metal surfaces.

Internal corrosion occurs in natural gas gathering lines and in natural and water gas transmission mains and distribution lines, storage tanks, etc., because of traces of moisture inevitably present in the gas. This corrosion is a major problem to the gas industry and has two main aspects, i. e., replacement of corroded equipment and service calls to adjust and clean consumer appliances. combat internal corrosion of pipe lines, the gas industry has resorted to oil fogging which consists of injecting an oil of low volatility as a fog into the gas stream in the lines to form a thin coating of oil on the metal surfaces. This expedient is disadvantageous however because the oil fogs will not be carried for long distances, for exam ple, in the fingers of a distribution line, wherein flow rates are low enough to allow even the finest fogs to settle, and the oil must be fogged into the gas stream at numerous points throughout the system to obtain adequate protection.

In addition to the corrosion problems of the gas industry there are the problems of transportation and storage of ferrous metals and ferrous metal products such as sheet steel, iron pipe, petroleum products storage tanks, machine parts etc. These metal objects are usually quite susceptible to the corrosive action of water vapor contained in the atmosphere. Where size permits it has been customary to wrap and seal them in moisture-proof wrappers or packages but this is impracticable in many cases. Even where practicable such precautions have not been wholly successful for despite the best efiorts corrosion still occurs since some water vapor is usually trapped in the wrapping or packaging when it is sealed, and additional moisture penetrates to the interior of the wrapping or packaging after it is sealed.

These and other problems are overcome according to my invention by providing an atmosphere containing vaporized ammonium naphthenate in contact with the metal surfaces to be protected from which atmosphere the corrosion inhibiting vaporized ammonium naphthenate deposits on the metal surfaces as a protective film. When injected into gas pipe lines, the vaporized ammonium naphthenate is carried, for example, in the case of natural gas, along with the gas stream from the gas field to the ultimate consumer and eventually coats and protects the interior surfaces of all metal in the entire system whether it be in the gathering lines, storage vessels, transmission mains or in the many fingers of distribution lines. Similarly the protective film deposited from an atmosphere containing vaporized ammonium naphthenate surrounding metal objects to be protected makes absolute sealing of the metal objects in moisture-proof wrapping or packaging unnecessary and negates the corrosive effect on the metal objects of the moisture trapped in the wrapping or packaging when it is sealed.

In one aspect of my invention an atmosphere containing vaporized ammonium naphthenate may be provided in gas gathering, storage, transmission and distribution equipment by fogging the ammonium naphthenate, preferably dissolved in a suitable solvent, directly into the appropriate gas pipe line. Either cold fogging, which consists of atomizing the inhibitor by a gas jet into the gas stream, or hot fogging, which consists of bubbling the gas through hot inhibitor contained in an externally heated tank, may be employed. I prefer the cold fogging procedure since I have found that there is some possibility of decomposition or at least darkening of the inhibitor from high temperature storage. Similarly an atmosphere containing vaporized ammonium naphthenate may be provided in closed containers by distribution in the liquid state.

The total amount of ammonium naphthenate required for gas line protection will vary with conditions such as the average line temperature, the amount of moisture present, and the amounts of pro-rust impurities. The quantity'of inhibitor required to be adsorbed on interior surfaces of the pipe will also vary depending on the pipe condition. For example, tests indicate that a monomolecular film would be adequate on clean steel. Pipes coated with a heavy rust layer, however, will require enough inhibitor to coat both the rust and the steel surface before corrosion is arrested. Inhibitor use at a high concentration followed by concentration reduction to a minimum amount is therefore recommended. Initial dosage may go as high as 10 pounds of ammonium naphthenate per million cubic feet of gas but after the interior pipe surfaces have been coated protection might be maintained using at little as 0.01 pound per million cubic feet.

In another aspect of my invention an atmosphere containing vaporized ammonium naphthenate is provided by vaporization of the inhibitor from a coating or impregnating composition applied to a wrapping or packaging material on the surface to be placed adjacent the metal surfaces. The coating or impregnating composition may consist essentially ofammonium naphthenate although materials such as, for example, urea and sodium bicarbonate may be added for pH control where required. The wrapping or packaging material advantageously is a fibrous material such as paper, cardboard, textile, wood, fibreboard, etc. With particular advantage, the wrapping or packaging material comprises a laminated fibrous material, for example, a crepe style kraft paper stock, the

laminar sections of which are laminated together by means of a fl xible moisture resistant laminant for example, asphalt, resinous type laminants, etc. The surface of the wrapping or packaging material to be placed adjacent the metal surface is coated or impregnated with ammonium naphthenate. The coating or impregnating composition may also consist essentially of a hydrocarbon vehicle and. ammonium naphthenate. The hydrocarbon vehicle must be inert, capable of forming a dispersion or solution of the ammonium naphthenate and capable of being applied to a packaging material. For example, the vehicle may be an oil of a suitable viscosity and flash point such as a kerosene, a gas oil cut, or a lubricating oil fraction. For example, desired concentrations of ammonium naphthenate may be dispersed in a bright stock or a neutral, e. g., a conventionally refined neutral of about SSU at F. The vehicle may comprise a wax such as a paraflin wax, a petrolatum or a microcrystalline wax, or a bituminous product such as an asphalt. The composition is applied as a coating to the wrapping or packaging material by an suitable means.

I The actual amount of inhibitor employed in coating compositions is ordinarily directly related to the amount of sealing of the wrapping or packaging material, the type of metal to be protected, the degree of exposure to'which the packaged metal will be subjected, and the period of time during which it is to be protected. enclosed or open air transportation or storage with constantly varying temperature and humidity are capable of affecting corrosion considerably. A coating composition containing ammonium naphthenate applied to a packaging material carrier should contain in general ammonium naphthenate in amounts of about A to grams and preferably 1 to 2 grams per square foot of treated carrier. Froman economic viewpoint, it is generally unnecessary to use more than about per cent by weight of ammonium naphthenate in the coating composition.

Ammonium naphthenate is a material the preparation of which is conventional. The commercial product generally is produced by adding ammonia to a mixture of naphthenic acids with acid numbers from about 180 to .300. Such acids are described in the literature as being .carboxylic acids containing a cyclopentane nucleus. I have found that ammonium naphthenates made from mixtures of acids having acid numbers of 230 and 260 have particular utility as vapor phase corrosion inhibiting agents. Ammonium naphthenates are generally in the form of a liquid or a soft gel. For purposes of injection into gas lines, however, they may be admixed witha suitable diluent such as kerosene to achieve a desired viscosity.

A corrosion test apparatus was designed to simulate gas pipe lines for testing the effectiveness of ammonium naphthenate as a vapor phase corrosion inhibitor. The apparatus included a unit containing oil well brine, a unit containing cotton, a first test chamber, a unit containing ammonium naphthenate, a second test chamber, a vacuum trap and a caustic absorber. The outlet end of the apparatus was attached to a vacuum line and a mixture of air and hydrogen sulfide was drawn slowly through the apparatus at a pressure of approximately 10 centimeters of mercury. The gas mixture was saturated with moisture in the brine containing unit and any moisture drops present were absorbed in the cotton containing unitprior to passage of the saturated gas mixture to thefirst test chamber. This test chamber contained a small metal test coupon which could be removed at time intervals for determining weight loss. The saturated gas mixture then passed through the inhibitor containing unit, a second test chamber identical with the first containing a similar removable test coupon, the vacuum trap, and the caustic absorber for removal of hydrogen sulfide and inhibitor before passage into the vacuum line.

Ammonium naphthenate dissolved in 50 per cent PD kerosene was tested in the apparatus for 21 days. The test coupon in the first test chamber weighed 24.1000 grams prior to the test and 24.0728 grams after cleaning at the end of the test, a 0.0272 gram loss in weight representing 0 per cent corrosion protection. The test coupon from the second test chamber, on the other hand, which was exposed to ammonium naphthenate, weighed 24.0860 grams prior to the test and 24.0850 grams after cleaning at the end of the test, a 0.0010 gram loss in weight representing 97 per cent protection.

In additional tests, samples of ammonium naphthenate, ammonium naphthenate containing compounds, and kraft papers coated with ammonium naphthenate and such compounds were tested for vapor phase corrosion inhibitor properties. The various samples tested were prepared in the following mannen,

Sample A A 440 gram portion of a commercial naphthenic acid with an acid number of 230 was partially neutralized to 72 per cent of the acid number with 2000 cc. of 2 per cent sodium hydroxide solution. This mixture was extracted with 500 cc. of pentane to remove unreacted acids and inert materials. The remaining soap solution was then acidified with sulfuric acid and was allowed to stand In particular,

until an acid and a water layer formed. The water layer was drawn oii and discarded. The acid layer was washed three times with 1000 cc. portions of water and the remaining acid weighed 250 grams which represented a 57 per cent yield. The purified acid was neutralized with a slight excess of ammonium hydroxide solution after which the mixture was heated until excess water and ammonia were removed.

Sample B A 100 gram portion of a commercial naphthenic acid with an acid number of 230 was heated and mixed with 20 grams of charcoal. The charcoal was removed by filtration while the mixture was still warm. The treated acid, which was much lighter in color, was heated to 150 F. and anhydrous ammonia was bubbled through the vigorously stirred acid until the solution was neutral to litmus paper. The neutralized acid was then mixed with urea and sodium bicarbonate to give a mixture containing by weight per cent ammonium naphthenate, 10 per cent urea and 5 per cent sodium hydrogen carbonate.

Sample C A kraft paper was coated by dipping the paper into a portion of Sample B and removing the excess with a piece of cloth.

Sample D stirred vigorously while anhydrous ammonia was bubbled through the solution for one hour. The reaction product was tested with litmus paper and it indicated a neutral soap. Four drops of mask odor was added for odor improvement.

Sample E A portion of Sample D was applied to a kraft paper using a conventional paper coating machine. The coating machine passed the paper through the inhibitor at 150 F., over a metering rod, and then over two rolls at 212 F. The hot rolls served to force the material into the paper. 14.4 pounds per ream or 2.3 grams per square foot.

The various samples were tested for vapor phase corrosion inhibition properties using the following procedure. A 200 milligram portion of the inhibitor or inhibitor containing compound was coated on the walls of a 4 ounce bottle, or a 2 inch by 2 inch strip of butcher paper coated with 60 milligrams of the inhibitor or inhibitor containing compound was placed therein. A freshly polished mild steel strip was suspended within the bottle from a hook attached to a cap andthe cap was screwed tightly into place. The assembly was then placed in an oven at F. for twenty-two hours to allow the inhibitor to precoat the test strip. At the end of the precoat period the bottle was removed from the oven and placedin an ice box at 40 F. for an additional two hours. Five milliliters of distilled water was then added and the bottle replaced in the oven for twentyfour hours after which the test strip was removed, dried and rated as follows:

A, Perfect.

13+ Less than A of total surface covered with rust. 13+, to 5% of total surface covered with rust.

B, 5% to 25% rust.

C, 25% to 50% rust.

D, 50% to 75% rust.

E, Over 75% rust.-

The results of these additional tests using the 4 ounce bottle test described above are indicated in the data given below. It should be noted, however, that the tests were conducted under extreme conditions of temperature and The compound was meter on the paper at humidity. In commercial use of my inhibitor these conditions are not likely to exist.

Sample Rust Test Results 1 a 85%, Medium to Heavy Rust.

13+, B+, 1% light rust. B+, 1% light rust.

B+, B+, %%light rust. B+, 13+, light rust.

1 Number of results indicate number of tests.

I claim:

1. A method of inhibiting corrosion of enclosed ferrous metal surfaces which comprises maintaining an atmosphere containing vaporized ammonium naphthenate in contact with the metal surfaces in amounts such that at least 0.1 pound of ammonium naphthenate is present for each million cubic feet of enclosed space.

2. A method of inhibiting internal corrosion of ferrous metal surfaces of gas gathering, storage, transmission and distribution equipment which comprises injecting into the gas stream flowing in such equipment from 0.1 to 10 pounds of ammonium naphthenate per million cubic feet of gas.

3. An article of manufacture which is useful in the packaging of metal objects in order to prevent their corrosion, said article being a sheet packaging material to which has been applied in amounts of about 0.5 to 5 grams per square foot of material a vapor phase corrosion inhibiting composition consisting essentially of ammonium naphthenate.

, 4. An article of manufacture which is useful in the 6 packaging of metal objects in order to prevent their corrosion, said article being paper to which has been applied in amounts of about 1 to 2 grams per square foot of paper a vapor phase corrosion inhibiting composition consisting essentially of ammonium naphthenate.

5. An article of manufacture which is useful in the packaging of metal objects in order to prevent their corrosion, said article being a material to which has been applied a vapor phase corrosion inhibiting composition consisting essentially of a hydrocarbon vehicle and ammonium naphthenate, the ammonium naphthenate being present on the coated material in amounts of about 0.5 to 5 grams per square foot.

6. An article of manufacture which is useful in the packaging of metal objects in order to prevent their corrosion, said article being paper to which has been applied a vapor phase corrosion inhibiting composition consisting essentially of a petroleum wax and ammonium naphthenate, the ammonium naphthenate being present on the coated paper in amounts of about 1 to 2 grams per square foot.

References Cited in the file of this patent UNITED STATES PATENTS 2,185,954 Ryner Jan. 2, 1940 2,587,249 Ulmer Feb. 26, 1952 2,629,649 Wachter Feb. 24, 1953 2,643,176 Wachter June 23, 1953 OTHER REFERENCES Ind. and Eng. Chemistry for December 1948, pages 2338 to 2347.

Claims (1)

1. A METHOD OF INHIBITING CORROSION OF ENCLOSED FERROUS METAL SURFACES WHICH COMPRISES MAINTAINING AN ATMOSPHERE CONTAINING VAPORIZED AMMONIUM NAPHTHENATE IN CONTACT WITH THE METAL SURFACES IN AMOUNTS SUCH THAT AT LEAST 0.1 POUNDS OF AMMONIUM NAPHTHENATE IS PRESENT FOR EACH MILLION CUBIC FEET OF ENCLOSED SPACE.