US2643176A - Compositions for protection of metals against corrosion - Google Patents

Description

Patented June 23, 1953 COMPOSITIONS FOR PROTECTION OF METALS AGAINST CORROSION Aaron Wachter and Nathan Stillman, Berkeley,

Calif., assignors to Shell Development Company, San Francisco, Calif., a corporation of Delaware 1 No Drawing.

Claims.

The present invention relates to novel compositions comprising a substantially solid material which contains, or is impregnated or coated with a vapor phase inhibitor which inhibits the corrosion of metals. More particularly stated, the present invention is concerned with various absorbent materials, e. g., cellulosic substances and their derivatives (modified paperacard-board, fibreboard, wood, cotton, cloth and the like) which are coated, impregnated, or otherwise contain one or more of the vapor phase inhibitors described below. I

Our copending applications Serial No. 663,608, filed April 1, 1946, Serial No. 668,015, filed May 7, 1946, and SerialNo. 675,886, filed June 1, 1946, disclose and claim variou methods of inhibiting corrosion by the introduction of certain types of vapor phase inhibitors; the present invention covers various substantially solid materials containing these vapor phase inhibitors, said materials being suitable for packaging or enclosing metals. 7

During storage, handling, transportation, etc. of objects having metal or metal-containing surfaces, especially those of various steels, aluminum, etc, it is often necessary to prevent the corrosion of these metals. Heretofore, the various methods used for this purpose have been unsatisfactory because of inadequate prevention of corrosion, ClliIlbElSOlIiGllBSS, and/or the necessity of using an excessive amount of labor and expenditure of time. v

Partially or completely enclosed metal parts are usually housed, packaged, boxed, enveloped, or placed in a container under such conditions that water vapor and air are either present, or are introduced to the metal parts at the time of their being disposed therein, or Water vapor with air enters through the enclosure walls after' the packaging. I

It is an object of the present invention to obviate the above and other defects, and to provide novel products or materials, which may be used as the'enclosing or packaging means per se, or therein, and which materials are capable of inhibiting corrosion of metal parts stored or disposed in such enclosing or packaging means and/or in said enclosure means containing said novel materials.

It has now been discovered that a product or Application October 28, 1946, Serial No. 706,098

composition comprising a substantially solid (particularly fibrous) material having disposed thereon or therein one or more vapor phase corrosion-inhibitors, the vapors of which have access to the contiguous, vapor space, prevents corroslon of corrodible metals disposed in the proximity of said compositions even in the presence of water vapor and oxygen. Suitable vapor phase inhibitors which are applicable according to this invention include salts of an organic nitrogen base with nitrous acid (organic base nitrites). Corrosion prevention was found to be effectively provided particularly by compositions comprising substantially solid covering materials containing organic nitrogen-base nitrites. It was also found that the vapor phase inhibitor should preferably have at least a vapor pressure of about 0.00002 mm. Hg at 21 C. Better results are obtainable with a vapor phase inhibitor having a vapor pressure greater than about 0.0001 mm. Hg at 21 C. while a more complete inhibition of corrosion is obtainable with avapor phase inhibitor having a vapor pressure greater. than about 0.001 mm. Hg at 21 C. The above mentioned compositions provide a highly satisfactory means for maintaining a corrosion-inhibiting atmosphere in the proximity of the metal.

The compositions of the present invention may be realized and/or utilized in a number of ways which may differ in detail but not in the essentialities of the invention. Thus, these compositions may be prepared: by impregnating various cellulosic formulations with the inhibitors, by impregnating any sheet, film, fabric, or other partially porous or absorbent material with the inhibitors. Preferably the solid material chosen for impregnation has at least a fibrous structure so as to allow for absorption of the vapor phase inhibitors between the individual fibers of the carrier material. Where a carrier material is not particularly absorbent, it may advantageously be coated with the present inhibitors.

It was found particularly effective to impregnate the vapor phase inhibitors into a kraft paper which is either substantially neutral or which may be rendered neutral or somewhat basic in reaction by incorporation or impregnation therein of basic-acting materials, preferably an organic amine or other organic nitrogenou base.

, Representative examples of solid materials which are suitable foruse in conjunction with the vapor phase inhibitors include: paper; textile fabrics, e. g. of cotton, wool, or silk; wood; modified or stiffened papers such as card-board, fibre-board, and laminated papers; synthetic fabrics or spun textiles such as rayons, polyamides, nylons, polyvinylbutyral, and polyethylene; asbestos, charcoal, activated charcoal, alumina gel, silica gel, etc. Any sheet or strip material made of the above fibrous substances may be used to prepare the novel compositions e. g. by coating. these substances with a solution, emulsion, or dispersion of the organic vapor phase inhibitofls) as IQl as the inhibitor may at least partially vaporize immune coating and thus be present in the contiguous atmosphere;

Impregnation or deposition of the vapor phase inhibitors described herein on any of the above solid materials is carried out by wetting, im-

mersion, or soaking of the material with a dispersion or solution of the inhibitoflsi prefer ably in a relatively volatile or'ganic solvent, in a mutual solution of water-e'oluble organic mate rial and Water, or in water alone. The impieg nation may also be effected by distributing a melt of the inhibitor(s) with or without a melt ing-point lowering agent, upon the surface of the solid carrier material. The fibrous materials may also be impregnated by contact with the vapors f e in ors,- I ?1.?? meth Q i pregnation, however, com rises deposition of the i ii ofl i fr m j rtlq i e SOB est. 9 l- Vnts used being evapor'ated by conventional methods, as by use of elevated temperatures, preferably not inegcess of abjout 120? F. with or without air-blowing or the l3 l;e. Suitable solvents include methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, acetone, methyl ethyl ketone, di-isopropyl ether, ihethyl acetate, andlike volatile p olar organic materials.

, I In many cases it is advantageous to treat or impregnate one or nore paper laminates with the vapor phase inhibitorts) and then fabricate these into finishedlaif'ninated fcomposition which contains outer layers (laminates) which are much less porous ondi stinctlyless impervious it the repo t .o t ein bi lo fif l ma ge t impregnatedlaminates which may be used for the interiorof a pa'ckage, or which are placed clo e to a corrodible metal, rn suchjeses, the outer laminate maybea metal foihsuch as tin or aluminum ,foil pi 'e'ferably ofsufficient thickiiessthat t contains rid m en Similar re sults have alsobeen obtainedby coating fo'ne side era vapor phase inhibitor-impregnated paper w ha fil b .waa ,w h'su ;h W x a r co taining the inhibitor(s)', it is possible to enclose a metal objec t with onelayer of the paper, and effectively preventcorrosion. In another embodimentof the invention, kraft paper waxed upon both sides wasw'armed to softenthe surface layer on one side thereof, and crystals or powder of an organic nitrogen base nitrite was then sprinkled upon the softened wax. The latter was thencooled, and excessvapor phase ine hibitor was shaken off. The resulting coated waxed paper, was found to bean effective supplier of corrosion-inhibiting vapors. Other wellknown coating ,materials may be used in place of waxv for dispersion or incorporation of the present. inhibitor(s) either before or after, disposal of the coating material upon suitable solid materials. As suchjco'ating materials, reference may. be made to: polyethylene blends of polyethylene with waxes, pol'yalkylene resins, alkyd resins j(e. g. of phthalicanhydride and glycerol), ethyl cellulose, polyamide resins, etc.

Vapor phase inhibitors which have been found applicable for use in the presentcompositions include salts of an organic nitrogen base with nitrous acid. Representative classes of nitrogenous bases which are suitable for preparing the present inhibitor-salts include such bases, for example, as: primaryamines, secondary amines, tertiary amines, cyclic secondary amines of the type of piperidine, oxazines, morpholine, thiazolines and pyrrolidine; and various nitrogenous bases such as urea, thiourea, hydrazines, hy-

droxylamines, amidines, and guanidine. In any ious substituent groups or atomic radicals may be present so long as the sum total basicity of the nitrogenous compound is approximately equal to or greater than the acidity of nitrous acid with which itforms a salt. Among the substituent groups, the alkyl ah'dcycloalkyl groups are preferred. Secondary amine nitrites, formed from nitrous acid and an amino nitrogen atom attached to a'sec'ondary earbon of an organic radical, as typified by 'di isobutyl amine nitrite, di-isopropylamine nitrite, dicyclohexylamine nitrite, piperazine nitrite, morpholine nitrite, or 2, i,e,6- tetraniethyl tetrahydro-3-oxazine nitrite are particularly effective vapor phase inhibitors.

'The basicity of'the yariousbasic nitrogenous constituents of the class of salts disclosed herein is de scribed, forle xaiiiple, the The Organic Chemistry of Nitrogen by V.'Sidgwick, 1937 edition. The many various organic nitrogenous bases are also described in fOrganic Chemistry byiaul Karrer, i938 edition v V More specifically and preferably, organic nitrogen base saltsof nitrous acid include the following nitrite salts of 1. Primary amines such as t (a) primary amines in which the amine group is attached to a secondary or a tertiary aliphatic carbon atom as in the following structural forles:

whereinR'i, R2 and Rs are hydrocarbon radicals which are aliphatic, alicyclic, heterocyclic, aromatic, or alkylated cyclic radicals, and may, if desired, fc ontai'n preferably not more than one olefinic double bond, or R1 and R2 are joined in the form of'a cyclo aliphatic or hetero-cyclicalip-hatic ring radical R3.

(D) primary amines in which the amine group is attached to an aralkyl group as in the following structural formula;

wherein R4 is an aromatic hydrocarbon radical, preferably a phenyl or allgyla'ted phenyl radical andnis an integer which is preferably 1 or 2;

(c) primary aliphatic amines, such as methyl amine, which react with nitrousacid in the p'res ence 'ofan excess of the amine to give a primary amine nitrite salt (as distinguished from a primary aliphatic amine which reacts with nitrous acid to yield nitrogen, an alcohol, or other reaction product's).

2. Secondary amines, such as secondary amines ,inwhich the amine group is attached to an aliphatic carbon atom, preferably a secondary or tertiary carbonatom, as represented by the following structural formulas:

wherein R; and Re are hydrocarbon radicals as in l (ci'and wherein R; and R2 may be joined in the form of a ring forming A R: NH

which is either N-alicyclicor contains in the R3 portion of the organic ring, atoms of the type of oxygen and/or sulfur.

3. Tertiary amines.

4. Quaternary ammonium bases pyridinium bases.

Specific examples of organic nitrogen bases suitable for preparation of the organic nitrogenbase nitrite salt vapor phase corrosion inhibitors of the present invention include:

Primary amines: methylamine, isopropyl amine, Z-amino-butane, tertiary butyl amine, 2- amino-l-methyl-pentane, various amyl, hexyl, heptyl, octyl, and higher homologous primary amines wherein the amine group is attached to a secondary or tertiary carbon atom; .cyclopentyl amine, alkylated cyclopentyl amines, .cyclohexylamine, mono-methyl cyclohexylamines, dimethyl cyclohexylamines, trimethyl cyclohexylamines, otheralkylated cyclohexylamines, bornyl amine, fenchyl amine, cycloterpenyl amines, pinyl amine, benzylamine, betaphenylethylamine, alkylated benzylarnines, tetrahydrobetanaphthylamine, allyl amine, betamethyl allyl amine, beta.- chloro allyl amine, and their homologs and analogs.

Secondary amines: di-methyl-, di-ethyl-, di-npropyl-, di-isopropyl-, di-butyl-amincs; various secondary amines derived from amyl, hexyl, heptyl, octyl, and higher homologous alkyl groups; methyl isobutyl amine, N-methy1 N- tertiary butyl amine, N alkyl N cyclohexyl amine, N-alkyl N-bornyl amine, di-bornyl amine, N-methyl N-cycloterpenyl amine, N-isopropyl N- l) -menthyl amine, N-alkyl N-benzyl amines and their homologs and analogs; dicyclopentyl amine, dicyclohexyl amine, alkylated dicyclohexyl amines; diphenylamine, dibenzylamine, di- (beta phenyl ethyl) amine; piperidine, piper azine, alkylated piperidines or piperazines; 1,4- alkylated and unalkylated oxazines such as morpholi-ne and 2,4,4,6-tetramethy1 tetrahydrol-1,3- oxazine; alkylated-L3-thiazine such as 2,4,4.,6- tetramethyl tetrahydro-3-thiazine.

Secondary amine type derivatives of alkylene diamines, such as: R1NH--R.:iNH-R3 wherein R1 and R3 may be like or different aliphatic, alicyclic, aralkyl, alkarylalkyl, heterocyclic, terpenic radicals, and wherein R2 is an alkylene or cycloalkylene radical. These R1 and R3 radicals for instance, may be isopropyl, butyl, cyclohexyl, benzyl, and/or bornyl radicals. The R2 radical is preferably an ethylene or propylene radical.

Tertiary amines: trimethyl amine, triethylamine, tri-n-propyl-amine, tri-isopropylamine, tributylamine, higher homologous and isomeric trialkylamines, variously N-substituted tertiary including amines having different organic radicals on the amino nitrogen atom, e. g., alkyl, alicyclic, bornyl,

'ienchyl, aralkyl, and like homologs and analogs;

and tertiary amine type derivatives of alkylene diamines.

Various organic nitrogenous bases particularly guanidine, alkylated guanidines, alkylated thioureas, and also diazoles, imidazoles, imida zolines, e. g., 2-heptyl-2-imidazoline, die-zines, pyrimidines, and the basic derivatives of these and other organic nitrogenous-base nuclei.

Quaternary ammonium bases; tetramethyl and higher tetra-alkyl ammonium bases; trimethyl benzyl, trimethyl cycloheXy1-, tributyl' decyl ammonium bases; various quaternary N-substituted ammonium bases having various organic radicals (of the type described above) on the quaternary nitrogen atom; pyridinium and alkylated pyridinium or qulnolinium quaternary ammonium bases having an alkyl, cycloalkyl, or aralkyl group on the quaternary nitrogen atom,

including methyl, butyl, cyclohexyl, benzyl groups basic in character.

The amount or concentration of the vapor phase inhibitor(s) which may be present in the compositions of this invention may vary within wide limits, but it is preferred to use them in the smallest efiective concentrations. These are usually between about 0.05 gm. and about 5.0 gm. of the inhibitor per square foot of the surface of the substantially solid material employed therewith. Especially satisfactory results are attained when the inhibitor concentration is such as to allow between about 1.0 gm. and about 15 gm. (or for average conditions about 6 gm.) of the inhibitor for each cubic foot of enclosed vapor space.

Stability of the present vapor phase inhibitors, particularly the stability of organic nitrogen base nitrite salts, is usually adversely affected when they are present in a composition or an environment which, on contact with or dispersion in water, yields an aqueous phase having a pH value of less than about 6. Also this stability is frequently adversely affected by elevated tempera tures, e. g., of the order of F. or F. These undesirable effects may be materially lessened or even entirely obviated by the simul taneous presence of a basic-acting agent, i. e. of an alkaline agent or a compound which reacts as a base in the presence of acidic-reacting materials. Preferably, it is advisable to use organic or inorganic compounds which, when dispersed in water, yield an aqueous phase having a pH value of at least 7. As such stabilizers, reference may be made to amines, guanidine, alkaline and alkaline earth metal hydroxides, carbonates and bicarbonatesand the like basic materials. The amount of such stabilizer should be between about 0.1% and about 25% by weight of the vapor phase inhibitor, although larger or smaller amounts may also be used.

In cases where the absorbent, substantially solid material has a demand or chemical affinity for an organic base, particularly for the amine employed to prepare the nitrite salt thereof as the inhibitor, it is preferable to treat such solid absorbent material with the amine until this demand is satisfied.

The present compositions are improved, at least for certain corrosion-inhibiting purposes, by having them contain a mixture of vapor phase corrosion-inhibitors, at least one of which has vapor pressure which is sufficiently high to pro vide immediate protection against corrosion while at least another inhibitor has a relatively low vapor pressure, which provides long-term corrosion-inhibition. The inhibitor with the low volatility is retained substantially in the vicinity gem-1 7s 7 of the inetalte be protected and does not escape to any material degree through the covering materials. In manycases; as with waxed paper or a metal foil enclosure, the high vapor pressure corrosion-inhibitor is also retainedeffectively in the vicinity of the metal.

The novel compositions of the present invention may be employed in a variety of ways for preventing corrosion of metals normally corrodible in the presence of air and water. The broad class of covering materials described herein containing the inhibitor(s) may be advantageously wrapped over, cloaked around, inserted near, draped over, or otherwise disposed in the immediate vicinity of the metal parts, so long as at least suflicient exterior "covering is "provided tokeep an effective corrosion-inhibiting amount of the vapors arising from the present compositions in the proximity of 'the'metal to be protected. -As illustrative examples, a layer of vapor phase inhibitor-containing paper was inserted between every six or seven layers of steel ball bearings. About 16 sq. ft. of vapor phase inhibitor pa'per was used per paper box containing approximately 2'50 steel bearings. The paper contained about 1 gm. of di-cyclohexylammonium nitrite per sq. ft. of paper. Inspection after one month showed the bearings were completely protected from rust, whereas the hearings in a control test were badly rusted. Also, a paper divider impregnated with di-isoproipyl or di-cyclohexyl ammonium r'ii'trite and used inside each package of two large steel half-bearings was found to keep the steel free from rusting. Also, a small piece of vapor phase inhibitor-containing paper was enclosed within a kraft-asphaltkraft laminate paper package containing bright bar steel stock. The latter remained unrusted, while like steel stock packaged in the same type of a package, but without the present compositions, became rusted. Many forms of steel military equipment including artillery guns, tanks, etc. have been draped loosely with vapor phase inhibitor-containing paper, and kept within storage rooms. The equipment was found to have retained its initial rust-free condition -during several months'of such storage. On the other hand, like equipment stored in the same manner, but without the presence of the present compositions, was found to have corroded.

For purposes of further illustration, reference will now be made to the following examples, it being understood that there is no intention of being limited to the specific conditions disclosed therein.

Example '1' Flat by 3 inch strips of thoroughly cleaned steel were wrapped in strong kraft paper which had been impregnated with di-cyclohexylammo nium nitrite from a solution containing 20 weight percent of the amine nitrite in a mixture of 75 weight percent methyl alcohol'and weight percent water. The thus-wrapped pieces of steel were placed in an envelopemade of kraft-asphaltkraft laminated paper and then exposed in a humidity cabinet to a temperature of 100 F. and 100% humidity fora period of seven days. At the end of this time the packages were opened including those of control tests (in which 'kraft paper unimpregnated with a vapor ph'aseinhibitor was employed). The steel strips wrapped with paper impregnated with the amine nitrite were found to be free of corrosion and shiny.

The steel in the control test was very badly corroded with rust over practically its entire surface. A like test was carried out in exactly the same manner except 2 percent by weight of di-cyclohexylamine in addition to the 20 weight percent .of the di-cyclohexylammonium nitrite in the impregnating solution was used to impregnate the wrapping paper. In this test the steel was also protected perfectly from rusting. Independent experiments indicated that the life of the dicyclohexylammonium nitrite was increased materially by the impregnation of the paper with di-cyclohexylamine.

. Example II 0.1 gm. pieces of 60 lb. kraftpaper were immersed-in a 2% by weight solution of *dicyclo hexylamine-in methanol-25% water solvent mixture for 10 seconds and then dried 5 minutes with warm air. One drop of 0.01 N sulfuric acid solution added to an entire extract of such treated paper changed phenoiphthalein indicator over to the acid side. A sample of the described amine-impregnated paper was then tested in a sealed glass tube stability test wherein 0.1 gm. of the paper onto which was deposited 0.05 gm. of dicyclohexylammonium nitrite, was subjected to the vapors from 0.50 ml. of water. A tube for a control test was prepared using a sample of the untreated paper. After the testing periods indicated below, the contents of the tubes were analyzed for nitrite content, and the following results were obtained:

Percent of Nitrate Ions resent Duration at 212 F. lnfl'ours Amine Treated g g i Paper Example 'II I The presence of guanidine nitrite in paper placed in the proximity of a strip of steel within an enclosure, completely prevents rusting and maintains the metal shiny. This test was carried out under conditions of humidity at a temperature of 150 F. for a period of seven days. Similarly, .it was found that a strip of brass was preserved free from corrosion when subjected to the co'nditionsdescribed herein. In the control tests the steel was badly rusted and the entire surface of the brass was covered with a blue-gray corrosion film.

Example IV Kraft paper was passed twice through methyl alcohol containing 20 weight percent of di-cyclohexylammonium nitrite and 3 weight percent of di-cyclohexylamine. The solvent was removed by then passing the paper over a metal drum dryer internally heated by infra-red lamps. Flat machined pieces of steel were wrapped in the thus-treated paper, and then placed in separate paper envelopes, the edges of which were sealed with wax. These envelopes were then suspended in a cabinet under conditions of 100% humidity and a temperature of F. After 300 hours of such exposure, only a few minute rust specks were present on the steel protected by the im- .pregnated paper. On the other hand a like machined piece of steel in the control test was covered with rust specks over its entire surface.

Example V The projecting outer surfaces of U-shaped machined steel strips were wrapped with kraft paper containing about 1 gm. of di-cyclohexylammonium nitrite per sq. ft. of the paper, and then overwrapped with aluminum foil having 0.005 inch thickness, the lapped edges of the foil being sealed with wax. A control sample of steel was wrapped in exactly the same manner except that plain unimpregnated kraft paper was used. These samples were then suspended in a cabinet having 100% of humidity, and maintained at 120? F. for 1000 hours. At the end of this period of time, there was no visible rust on any portion of the steel pieces packaged in the containers hav-v ing the inhibitor. On the other hand, the steel of the control sample was badly rusted over more than 75% of its surface.

percent solution of di cyclohexylammonium nitrite in methyl alcohol, and was found to contain 1.6 grams of this organic nitrite salt inhibitor. A third tube (as a control) contained no inhibitor.

A 5-inch section of each of said three tubes was placed in a 1 inch by 6 inch Pyrex test tube. A inch by 5 inch steel strip was placed inside each paper tube and the glass container test tube thereof was stoppered and maintained one hour at 120 F. Just before testing, the steel strip was polished with No. 2/0 emery paper. The tests were continued for one hour at 120 F., and then the solid stopper was replaced by a cork stopper having a inch diameter hole, the test tube being then suspended open end down in a standard humidity cabinet held at 100 F. and 90% humidity. The results obtained are summarized in the following table:

. Appearance at Time in Hours Paper Tube Containing- Di-isopropyl ammonium nitrite no rust. no rust n ust no rust no rust no rust. D i-cyclohexyl ammonium nitrite. undo-.. mdo

do Do. None (control) rusting fine rust on faces, lightly more very little 11ttlechange httlechange.

on edges progressive rust. change.

edges. rusting;

B The lower one inch of tubes were moist.

Example VI rusted. For further comparison, like steel parts were first covered with a coating of a petroleum oil and then maintained at room temperature for eleven months. These steel parts showed a considerable number of rusted areas.

Example VII By impregnating two parts by weight, of asbestos fiber with one part of di-cyclohexylammonium nitrite and then using this composition as dunnage for packaging steel articles, it is possible to keep the steel surfaces of such articles free from rust.

Example VIII Four-ply spiral-wound kraft paper tubes, 18 inches long and 0.75 inch outside diameter were used in the following tests. The layers of the paper tubes were held together with casein glue, the pH of the tube was 9.4 and titration to a pH of 7 of the water extract of these paper tubes before impregnation showed that on the averageeach one of them contained approximately 0.002 equivalent of basic-reacting material.

One of these tubes was impregnated with a solution formed by dissolving 40% by weight of di-isopropylammonium nitrite in a 50 weight percent aqueous solution of isopropyl alcohol. The tube was found to contain 3.5 grams of diisopropylar'nmonium nitrite. Another one of these times was impregnated with a 20 weight specimens.

Example IX Two steel bolt specimens were prepared by solvent washing, followed by wire brushing and then screwed into the fitting nut just far enough that the latter actedas a. supporting base in which the bolt stood in avertical position. Each of the prepared bolts was placed upright upon, the respective bottom of each of two 2-ounce sample bottles. In a prepared recess in the cork of the bottle containing the first of these specimens there was placed a small piece of cotton which had absorbed thereon 0.2 ml. of distilled water and 0.1 gm. of morpholine nitrite. The same amount of distilled water but without any vapor phase inhibitor, was absorbed in the same manner on a piece of cotton inserted into a prepared recess of the cork of the other of the two bottles. The respective bolts were not in contact with the cotton or the materials absorbed in the cotton. These corked bottles were allowed to stand at normal room temperature for a period of 76 days. At the end of this test period, the steel specimen which was subjected to the action of morpholine nitrite vapors was free from rust. The surface of this steel specimen was shiny as it had been at the start of the test. On the other hand, the other steel specimen was so severely rusted that the surface of it had a rusty appearance and had lost its original shiny polished surface.

Example X Two inch low-carbon steel plates were machined to a inch by 3 inch strip and wire brushed to a bright metallic sheen. An inner wrap of neutral kraft paper and an outer wrap of laminated metal foil paper provided with an internal coating of a thermoplastic resin was provided around one of the described steel-plate The outer laminated metal foil wrap was heat sealed. The other steel plate was packaged in the identical manner except that the inner wrap of the neutral kraft paper, which in each instance measured 2 inches by 4 inches, was impregnated by dipping it in a 50% (by weight) 11 aqueous solution of morpholine nitrite. After dipping, the paper was dried by suspension'for about 10 minutes in an air blast maintained at approximately 50 C. After such drying, the kraft paper contained approximately 0.1 gm. of the inhibitor.

Both specimens, after packaging, were inimersed in synthetic sea water prepared according to U. S. Bureau of Ships Specification 14-0-45 (INT) (1934), for a period of 26 days, the water being maintained at a temperature of approxi mately 30 C. during the test. At the end of the test period these packages were opened. Itwas discovered that the steel plate wrapped in paper which did not contain any amine nitrite was badly corroded with rust. On .the other hand. they steel plate packaged with the amine nitrite in theinner wrap retained its original. polished and unblemished condition and appearance.

Example XI Vapor phase corrosion tests were made with di-- isopropylammonium nitrite to determine the effects on specimens of S. A. E. 1020 steel and 24 ST aluminum in coupled combination and also on the S. A. E. 1020 steel attached to asteel bolt. A one-half by one inch specimen of the metal alloy, coupled by a steel bolt through holes in each metal sample, was suspended in the vapor space of an 8 oz. wide-mouth bottle by means of a wire hook in a parafiined cork stopper of the bottle. A 16 sq. inch piece of kraft paper impregnated with approximately 0.2 gm. of diisopropyhammonium nitrite, was placed on the bottom of a bottle of one series to be tested, while duplicate bottles cont'aining the metalsfor control experiments were prepared containing the same amount of untreated. kraft paper. .To each of the containers was added 012ml. of distilled water. All of thebottles were maintained at 30 C. for '73 days, after which time the specimens were removed, uncoupled, inspected and the weight loss determined after removal of any corrosion product, when present. It was found that, in the cases where ,di-isopropylammonium nitrite was used, there wasno corrosion on either metal on the aluminum couple, and no corrosion (rust) on t e A. 02, t l d n the oi ltha d; in the control experiment (in which no di-isopropylammonium nitritewas used) there was bad and uniform rusting of the steel and some corrosion of the aluminum on the S. A. E. 102 0 steel-24 genome 12 line of Organic Nitrogen Compounds, University Lithoprinters, Ypsilanti, Michigan (1945), page 59, namely, to designate a radical obtained by the loss of a hydrogen atom from any hydrocarbon.

The present application is a continuation-in part of the copending application Serial No. 557,358, filed October 5, 1944, now abandoned.

We claim as our invention:

1. A substantially solid material capable of inhibiting corrosion of a metal by an atmosphere containing oxygen and water vapor, which comprises paper containing between about 0.05 gram and about 5.0 grams per square foot of the sur-' face of said paper, of di-isopropyl amine nitrite and a stabilizing amount of a basic-reacting agent.

2. A substantially solid material capable of inhibiting corrosion of a metal by an atmosphere containing oxygen and water vapor, which com-.

prises paper containing between about 0.05 gram and about 5.0 grams per square foot of the surface of said paper, of di-cyclohexyl amine nitrite and a stabilizing amount of a basic-reacting agent.

3 A material capable of "inhibiting corrosion of a metal by an atmosphere containing oxygen and Water vapor, which comprises a substantially solid fibrous material containing between about 0.05 gram and about 5.0 grams per square foot of the surface of said fibrous material, of dicyclohexy amine nitrite and a stabilizing amount of a basic-reacting agent. A

4. A material capable of inhibiting corrosion of a metal by an atmosphere containing oxygen and water vapor, which comprises a substantially solid fifrous material containing between about 0.05 gram and about 5.0 grams per square foot of the surface of said fibrous material, of diisopropyl amine nitrite and a stabilizing amount of a basic-reactingagent. I

5. A material capable of inhibiting corrosion of a metal by an atmosphere containing oxygen and Water vapor, which comprises a substantially solid fibrous material containing between about 0.05 gram and about 5.0 grams per square foot ST aluminum couple, and fine rush specks over the entire surface of the steel.

Example XII A by 3 inch specimen of. aluminum was wrapped in 2 by 4 inch pieces of kraft paper im' pregnated with di-isopropylammonium nitrite which was then placed in another envelope made by folding 5 by 5 inch pieces of Grade A paper; the last envelope was then sealed with a pressure-sensitive,. waterproof tape. Another aluminum specimen was similarly prepared, the only difference being thatitwas wrapped in an untreated piece of the said kraft paper. The envelopes or packages thus produced were suspended over water at 30 C. for 2 months, whereupon it was found that, whereas the aluminum specimen wrapped in the paper treated with diisopropylammonium nitrite was not corroded, the aluminum specimen wrapped in the untreated paper had considerable white corrosion.

The term hydrocarbyl is used herein in accordance with the definition in Degering, Outof the surface of said'fibrous material, of dicyclohexyl amine nitrite.

6. A material capable of inhibiting corrosion of a metal by an atmosphere containing oxygen and water vapor, whichcomp'rises a substantially solid fibrous material containing between about 0.05 grainandabout 5.0 grams per square foot of the surface of said fibrous material, of a dicycloalkyl amine nitrite salt having a vapor piessure of at least about 0.00002 mm. Hg at 2 C.

7. A material capable of inhibiting corrosion of a metal by an atmosphere containing oxygen and water vapor, which comprises a substantially solidfibrous material containing between about 0.05 gram and about Sgrams'per square foot of the surface of said. fibrous material, of diisopropyl amine nitrite.

8. A material'capable of inhibiting corrosion of a metal by an atmosphere containing oxygen and water vapor, which comprises a substantially solid fibrous material containing between about 0.05 gram and about 5 grams persquare foot of the surface of saidjfibrous material, of a secondary amine nitrite salt having a vapor pressure of at least about 0.00002 mm. I-Ig at 21 C.

9. A material capable of inhibiting corrosion of a metal by an atmosphere containing oxygen and water vapor. which comprises a substantially solid fibrous material containing a corrosioninhibiting amount; of an organic nitrogen-base nitrite salt of an unsubstituted hydrocarbyl amine, said salt having a vapor pressure of at least about 0.00002 mm. Hg at 21 C.

10. A material capable of inhibiting corrosion of a metal by an atmosphere containing oxygen and water vapor, which comprises a substantially solid fibrous material containing a corrosioninhibiting amount of an organic nitrogen-base nitrite salt having a vapor pressure of at least about 0.00002 mm. He at 21 C.

AARON WACHTER. NATHAN STILLMAN.

References Cited in the file of, this patent 14 UNITED STATES PATENTS Number Name Date 1,387,132 Decherd Aug. 9, 1921 1,847,711 Calcott et al Mar. 1, 1932 2,148,862 Kern Feb. 28, 1939 2,304,950 Parker et a1 Dec. 15, 1942 2,323,369 Briggman July 6, 1943 2,344,404 Giloy Mar. 14, 1944 2,416,734 Boggs et a1 Mar. 4, 1947 OTHER REFERENCES Ex parte Appeal Number 5286, April 4, 1947, (Case Number 213) 29 J. P. O. S. 456.

Corrosion Handbook by Herbert H. Uhlig. Published by John Wiley and Sons, Inc., New York, New York. in 1948. V V

Claims (1)

10. A MATERIAL CAPABLE OF INHIBITING CORROSION OF A METAL BY AN ATOMSPHERE CONTAINING OXYGEN AND WATER VAPOR, WHICH COMPRISES A SUBSTANTIALLY SOLID FIBROUS MATERIAL CONTAINING A CORROSIONINHIBITING AMOUNT OF AN ORGANIC NITROGEN-BASE NITRITE SALT HAVING A VAPOR PRESSURE OF AT LEAST ABOUT 0.00002 MM. HG AT 12* C.