AU607617B2 - Rust and corrosion protection - Google Patents

Description

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ATPU1CATION ACCEPTED AND AM*NDMENTS ALLOWED 0 Ir-.a 1 COMMONWEALTH OF AUSTRAIAM PATENTS ACT 1952 COMESfPlEI~Q NAME ADDRESS OF APPLICANT: ft ft #4

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1114 Avenue of the Americas New York New York 10036 United States of America NAME(S) OF INVENTOR(S): Nathan C. REDWINE David A. LITTLE John W. RUDOLPH Gary G. ENGSTROM ADDRESS FOR SERVICE: DAVIES COLLISON Patent Attorneys 1 Little Collins Street, Melbourne, 3000.

IThis document contains the anacndnients made undcr ISection 49 and is correct for printing.

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COMAPLETE SPECIFICATION FOR THE INVENTION ENTILED: Rust and corrosion protection The following statement is a full performing it known to me/us:description of this invention, including the best method of 1 i

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Insert place and date of signature.

Signature of declarant(s) (no attestation required) Note Initial all alterations.

4. The basic application...,,,.., referred to in paragraph 3 of 'this Declaration was the first application......... madein a Convention country in respect of the invention the subject of the application.

Declared at Columbia, MD USAhis tay of May, 1989 William W. McDowell, Jr.

Assistant Secretary DAVIFS (OLLISON, MELDOURNE and CANBERRA.

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ii Se t I FIELD OF THE INVENTION This invention relates to providing rust and corrosion protection for articles made from iron-based metals, and more particularly to treating articles having surfaces of iron, mild steel and the like with hydroxylamine compounds to inhibit the corrosion of said surfaces.

BACKGROUND OF THE INVENTION 10 a a Sa a a a a* oooo 15 a a Ct I e C a at S a a 6 2 The processing of metal articles from iron, mild steel and the like often exposes the cleaned surfaces of these articles to moisture and oxygen conditions which are favorable for rusting or corrosion of these surfaces.

For example, iron-based shipping drums are commonly cleaned of residue and stripped of paint for reuse, but processing and storage of the cleaned drums without further treatment can lead to their rusting, particularly when exposed in air to moisture or humidity. Similarly the cutting of steel parts from mild steel is often accompanied by cooling with an aqueous solution, and without treatment, rusting can occur for example during high-temperature exposure to the cooling solution, upon recondensation of water on the surfaces of the part during processing, or upon storage in a moist or humid environment.

Treatment for the prevention of rusting and corrosion has thus become an important aspect to processing of articles having exposed surfaces of iron, mild steel, or the like. Conventional treatments have used substances such as phosphate, nitrite, ethanolamines, oils, and -3soaps, alone or in combinations to chemically inhibit corrosion. However recent environmental regulations and performance standards have resulted in an industry search for alternative technologies which minimize disposal concerns for the treatment solution, and the amount of residual material which might be left on the treated article.

U.S. Patent No. 4,067,690 discloses that hydroxylamine has been used in certain anti-corrosion applications, and that hydroxylamines and their salts demonstrated an oxygen scavenging activity which could be used to control corrosion of iron and steel surfaces.

4 Ellis et al., "The Oxidation and Degradation Products of Volatile Oxygen Scavengers and their Relevance in Plant f Applications", "Corrosion 87" 1987, published by O Publications Dept., P.O. Box 218340, Houston, S. Texas 77218, discusses the passivating properties i oof diethylhydroxylamine including the gradual o oo establishment of a protective layer at high temperatures, 0 0 as well as the nature and significance of its oxidation and thermal decomposition products.

Of course the formation of protective layers at high j o* temperatures over a period of months would be unsuitable o for many metal processing operations, both from an energy and time standpoint. Moreover the relatively thick, °o black layers of deposit associated with long-term passivation can interfere with later coating or processing steps for metal articles.

SUMMARY OF THIS INVENTION It has now been found that articles having clean surfaces of iron, mild steel or the like can be protected 901205,immdat 901205,immdat070,a:\36318gra.res,3 c. I -r ~-il~u~uYII~l against rust and corrosion by short term exposure to an aqueous treatment containing between 0.001% and 98% by weight of certain hydroxylamine compounds.

It is an object of this invention to provide at least temporary corrosion protection for articles which have surfaces of iron-based metals which are suceptible to rusting.

It is another object of this invention to provide a rust protection program which employs an agent having minimal disposal concerns.

These and other objects of this invention will become apparent from the description of the invention provided herein.

DETAILED DESCRIPTION "so In accordance with this invention cleaned surfaces of articles made of iron, mild steel and like metals are o o0 contacted with an aqueous treatment containing certain O 0 o 20 hydroxylamine compounds. In general the treatment oo o compositions used in this invention include a N hydroxylamine compound having the structural formula ooo1

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o o| o0 o 0 So 25 N-OH SR and R 2 may be the same or different and are each selected from the group consisting of hydrogen, lower CCCC 30 alkyl, preferably having between 1 and about 8 carbon C 4i.

atoms, and aryl, preferably phenyl, benzyl and tolyl.

Said alkyl and aryl groups may optionally have one or more hydroxyl or halogen substituents.

Specific examples of hydroxylamine compounds usefully employed herein include hydroxylamine, nitrogen substituted derivatives thereof. N,N-diethylhydroxylamine is commercially available and is considered to be a particularly useful hydroxylamine compound. Water soluble salts of the hydroxylamine compounds of said structural formula may also be used, such as chlorides, sulfates, acid sulfates, phosphates, and sulfites.

In operation, the clean metal surfaces are contacted with the treatment composition within a short time after they are acquired, before substantial corrosion has begun and while the surfaces are still essentially free of rust.

SThis can be accomplished by immersing the article in a 4 solution containing at least about 0.001 weight percent about 10 ppm) of the hydroxylamine compound. For Smost applications a hydroxylamine compound concentration ,.20 of between 1000 ppm and 10,000 ppm is preferred, although 0 treatments using up to 98% hydroxylamine compound are considered to fall within the scope of this invention.

Without limiting the invention to a particular theory of operation, the exposure of the metal surfaces to the S#'425 hydroxylamine compound is believed to react with ferric oxide on the surface of the article in accordance with the 4 <cpublished reaction: (C2H 2NOH 6Fe203 4Fe304 CH CH=NOH +CH CHO+ H0 1 (j 4 1: '8i~ I t I I a oo o o 0 o o 00 000000 0 0 0 00 00 o 00 0 00 00 00 0000 00 00 000 00 O0 0 00 O 0 11 0 0 Od 0 00 0 0 a 0009

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ttOQ Accordingly, the hydroxylamine compounds of this invention are considered to be used in an amount effective to facilitate the formation of a thin protective layer comprising ferriferrous oxide on the surfaces of the treated article.

Exposure of the surfaces to treatment in accordance with this invention is shoit term, generally 1 hour or less. Accordingly, the relatively thick black magnetite deposits often observed with longer term high temperature exposure of mild steel surfaces to oxygen scavengers such as hydrazine and diethylhydroxylamine, can be avoided.

Indeed, the blackened surfaces of such long-term exposure are often considered undesirable, because the thick deposits can interfere with further processing of the article; and routine long term exposure of metal parts would itself generally be considered impractical for the processing of the metal parts. Nevertheless, the article surfaces treated in accordance with this invention are protected, at least temporarily, against rusting and 20 corrosion by exposing them to treatment with an effective amount of hydroxylamine compounds for about 10 seconds or more, preferably between about 30 seconds and 3 minutes, so that rusting and corrosion are inhibited. The treated article can be transported and stored for later finishing or further processing with its susceptibility to rusting and corrosion greatly reduced. Without treatment, the metal surfaces would continue to progressively react with oxygen, thereby corroding the article and forming corrosion products such as Fe 2 03 The invention may be practiced over a broad pH range, and the pH of the treatment solution is generally kept between 2 and 13. Preferably the pH is at least about 7,

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4: I L i most preferably at least about 9, especially where jhydroxylamine vaporization from solution is desired. The treatment systems are commonly at atmospheric pressure 0 psig) but can be pressurized as desired in conformance with the processing of the article, for example, up to about 50 psig, or sometimes more.

Application temperatures are relatively low, generally between 10 0 C and 120 0 C. It may be desirable for many process applications to limit treatment exposure times to say, roughly about two minutes, and for practical as well as performance reasons contact temperatures of between about 500C and 100°C may thus be preferred so that a corrosion-inhibiting treatment dosage may be provided at relatively low concentrations of hydroxylamine compound.

As indicated above the articles may be contacted with the aqueous treatment by immersing them in a solution *o,0 0 containing the hydroxylamine compound. Alternatively, an aqueous solution containing the hydroxylamine compound may 0 0 be sprayed onto the surfaces of the article for the 0 0 0o 20 requisite treatment period. It is noted however that the hydroxylamine compounds used in this invention are oo oo generally volatile, and it is considered within the scope of this invention to contact the article surfaces with an oooo aqueous vapor containing the hydroxylamine compound or 0o 025 with a condensate thereof.

0 0 4 After contacting the surfaces with the aqueous o treatment containing hydroxylamine compound in accordance with this invention, the surfaces are preferably dried.

Drying may be conveniently accomplished by evaporation cc( 30 either at room conditions, or by heating the articles.

7 1 1 I I I Other corrosion inhibiting compounds may be used in combination with the hydroxylamine compounds of this invention provided they do not interfere with the protective effect achieved hydroxylamine compound. For example nitrites and certain amines are believed compatible with the hydroxylamine treatment of this invention, as are molybdates which can be advantageously employed in combination with the hydroxylamine. It is noted however that hydroxylamine compounds such as diethylhydroxylamine are considered to be generally non-toxic, and thus when used alone provide minimal handling and disposal concerns.

As noted above the invention is practiced with iron-based metals which have surfaces that, when cleaned, are susceptible to rusting. Accordingly metal surfaces of iron or mild steel may be advantageously treated in accordance with this invention; while metal surfaces of stainless steel and the like, which are already 00o o rust-resistant, would not normally be treated in 0 0 0 20 accordance with this invention. The clean surfaces may be ,O 0o acquired by physical or chemical treatment of unclean 0 surfaces, or by providing new surfaces as by the cutting of steel sheet into smaller pieces.

Practice of the invention will become further 00 i o o0 25 apparent from the following non-limiting examples: a a a EXAMPLE I To simulate the contact of steel parts with a spray ic- 30 or splash of cooling water, two clean ASTM D-1384 steel Scoupons (SAE 1020) were sprayed with drops of water having a total hardness of about 310 ppm as CaCO 3 The coupons Swere observed shortly after spraying to have rust spots.

The coupons were stacked to simulate stacked steel parts -21 formula ~llii~ i' ii :1

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and observed again after 4 days. Several rust spots were observed after 4 days. Additional runs were made in which various treatment compositions were added to the water sprayed onto the coupons. The results are shown in Table

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TABLE I Treatment Coupon Appearance After After Spraying 4 days clean clean C IC 6 0 0 4r o0 0 60 6 6 6 o c 4 00 4 to 4 4' C 44 4 64 (t

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1000 ppm morpholine, 400 ppm molybdate and 280 ppm benzotriazole 500 ppm morpholine, 200 ppm molybdate and 15 140 ppm benzotriazole 250 ppm morpholine, 100 ppm molybdate and 70 ppm benzotriazole 1000 ppm morpholine 20 500 ppm morpholine 100 ppm morpholine 1000 ppm N,N-diethylhydroxylamine 25 500 ppm N,N-diethylhydroxylamine 100 ppm N,N-diethylhydroxylamine 10,000 ppm sodium nitrite 7 ppm orthophosphate 3.5 ppm orthophosphate clean clean clean clean clean clean clean clean clean clean clean rust spot rust spot rust spot rust spot rust spot clean rust spot rust spot clean rusting rusting F ';t 1 i 'i -L 1 TABLE I Treatment Coupon Appearance After After Spraying 4 days ppm orthophosphate and 1000 ppm morpholine clean rusting ppm orthophosphate and 1000 ppm morpholine clean rusting ppm orthophosphate and and 1000 ppm N,N-diethylhydroxylamine clean clean 7 ppm orthophosphate and 1000 ppm N,N-diethylhydroxylamine clean clean 1000 ppm morpholine, 400 ppm molybdate, clean clean 200 ppm benzotriazole Sand 1000 ppm N,N-diethylhydroxylamine 1000 ppm morpholine, clean clean 400ppm molybdate, and a 20 280ppm benzotriazole SIt will be evident from Table I that the hydroxylamine compound could be used to provide immediate rust protection; and that 1000 ppm of diethylhydroxyla- Smine, either alone or in combination with other agents S° 0 a0 acould be used to provide rust protection over several Sdays. It is noted that the spray used in this example 7. provided a treatment of limited intensiveness. It is considered that higher temperatures, lower water corrosivity, and/or longer exposure times to treatment 4ii would enable even the lower levels of the hydroxylamine compound 100 ppm and 500 ppm) to achieve greater corrosion protection.

EXAMPLE II To simulate the processing of steel parts in a humid environment, two clean ASTM D-1384 steel coupons (SAE 1020) were placed over the top of a beaker of water having a temperature of about 760 C for about 15 minutes. The coupons were then turned over, and placed in the humid environment over the beaker for another 15 minutes. The coupons were observed to have overall rusting of their surfaces. The coupons were stacked to simulate stacked steel parts and observed again after 4 days. Overall rusting was again observed after 4 days. Additional runs o 00 o o. were made in which various treatment compositions were added to the water in the beaker. The results are shown 0 0 o"0 in Table II.

0 o 0 So TABLE II o 0 1 Sj 000 a o a Soo 25 0 0 0 0 00

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Treatment Coupon Appearance After After Exposure 4 days 1000 ppm morpholine, 400 ppm molybdate and 280 ppm benzotriazole 500 ppm morpholine, 200 ppm molybdate and 140 ppm benzotriazole clean light rust rust specks rust specks i i.

'i 1 I a; '1 1 0 Treatment TiABLE II Coupon Appearance After After Exposure 4 days rust specks rust specks

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(i t, .i I at t t I a. C (acr ca a 250 ppm morpholine, 100 ppm molybdate and ppm benzotriazole 1000 ppm morpholine 500 ppm morpholine 100 ppm morpholine 1000 ppm N,N-diethylhydroxylamine 500 ppm N,N-diethylhydroxylamine 100 ppm N,N-diethylhydroxylamine 10,000 ppm sodium nitrite 20 7 ppm orthophosphate 3.5 ppm orthophosphate 3.5 ppm orthophosphate and 1000 ppm morphjline 7 ppm orthophosphate and 1000 ppm morpholine 3.5 ppm orthophosphate and 1000 ppm N,N-diethylhydroxylamine 7 ppm orthophosphate and 1000 ppm N,N-diethylhydroxylamine rust specks overall rust specks overall rust specks overall rust specks overall rust specks overall rust specks tiny rust specks overall rust overall rust rust specks rust specks tiny rust specks tiny rust specks rust specks rust spots rust spots rust spots rust spots rust spots rust specks heavy rusting heavy rusting rust specks rust specks clean clean

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t, 11 3~~n TABLE II Treatment Coupon Appearance After After Exposure 4 days 1000 ppm morpholine, 400 ppm molybdate, 200 ppm benzotriazole and 1000 ppm N,N-diethylhydroxylamine 1000 ppm morpholine, 400ppm molybdate, and 280ppm benzotriazole 1000 ppm inorpholine, 400 ppm molybdate, and 280 ppm benzotriazole tiny rust specks clean rust streak clean except for rust streak faint rust dots faint rust dot on a ti, 4) 00 P' a 0 ,2 0L 0 .1.0(I 1,3O It is noted that the diethylhydroxylamine used in these runs was volatile, and it is accordingly believed that some of the hydro..ylamine volatilized and condensed along with the water in these runs, thereby providing some corrosion protection even where the parts were exposed to rucondensed water. However, no measurements were made of the concentration of hydroxylamine in the vapor which contacted the coupons during the various runs.

Accordingly, the beaker tests of this example which utilized diethylhydroxylamine may not have all successfully simulated the protective conditions intended; and the results of the beaker tests in Table II may thus not all be representative of the rust-inhibiting effectiveness which can be achieved in accordance with this invention by contacting clean steel parts with a rust-inhibiting dosage of an aqueous vapor containing 64 4 1 I

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'2 i where R 1 and R 2 may be the same or different, and are selected from the group consisting of hydrogen, lower alkyl, and aryl, and water soluble salts thereof; and

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drying said article.

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hydroxylamine comound or a condensate thereof. Indeed the improved results in Table II where the hydroxylamine was used in combination with other agents may at least in part be attributable to improved volatization of the hydroxylamine after addition of those other agents.

EXAMPLE III A field study was made at a facility where metal parts were produced from sheet metal using robotic cutting torch tables. During a typical cutting operation a cleaned piece of steel, about 0.25 to 1.5 inches thick and a a. C up to about 6 feet long and 10 feet wide, is placed on a .1 grate table) above a reservoir of about 2,000 V 15 gallons of cooling water, and is flame cut to the desired shape. As cutting proceeds metal slag falls through the grate into the reservoir where it is quenched. The slag causes evaporation from the cooling water reservoir as it is quenched, and the impact of the slag on the surface of 20 the reservoir can also cause splashing of the cooling i G°o water toward the parts supported on the grate. In addition, the cooling water is circulated to the cutting 4 1 C torch apparatus which sprays the cooling water in a i circular pattern around the torch flames to cool the metal and to prevent its warping.

Cleaned steel surfaces exposed to moisture during the metal cutting process are susceptible to rusting.

L C Rust-bearing parts must often be cleaned and reconditioned before other process steps such as painting may be effectively practiced. Accordingly, in order to inhibit rusting during the cutting process, corrosion inhibitors 14 i 4.I_ T 1, 4*.

i~ar 4, ri 0 9 14 4 t 0 1 SO 00 0r 0 00 0 0 00 00 9 49 9 4 are added to the cooling water. For example, the cooling water was treated with a mixture of about 200 ppm of molybdate, about 25 ppm benzotriazole, and about 900 ppm morpholine. However, this treatment did not prevent rust formation on the underside of the metal which was not sprayed and was exposed to evaporation from the reservoir.

Further addition of about 1000 ppm of N,N-diethylhydroxylamine along with this mixture prevented flash rusting of the metal, including its underside. The parts produced using the mixture containing the hydroxylamine compound were sufficiently clean for further processing.

EXAMPLE IV 15 Laboratory studies were made using samples of mild steel which had been cut from new standard steel shipping drums. The protective oil on the surfaces of the coupons was cleaned therefrom using l,l,l-trichloroethane, and the observed coupons were allowed to air dry. Some of the samples were treated by immersing them in an aqueous wash having a pH of between 9 and 10 and a temperature of about 82 0 C for about 23 seconds, followed by immersing them in a treatment solution containing about 0.1 weight percent N,N,-diethylhydroxylamine and having a temperature of 25 about 82 0 C for about 61 seconds, and then immersing them in a treatment rinse containing about 0.025 weight percent N,N-diethylhydroxylamine and having a temperature of about 82 0 C for about 23 seconds. The treated coupons were then dried in an oven for about 3 minutes at about 1210C.

Other samples were similarly processed except that the treatment solution step and the treatment rinse step did not contain any hydroxylamine compound.

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L- 11 l Samples which had been processed with and without hydroxylamine compound were each exposed to the open room environment. Other samples which had been processed with and without hydroxylamine ccnpound were suspended in air within a container having standing water to simulate a humid storage environment. The samples were visually observed for 14 days. Rust appeared within 24 hours on the sample in the humid environment which had been processed without exposure to hydroxylamine compound.

After about 72 hours traces of rust began to form on the sample in the open environment which had been processed without exposure to hydroxylamine compound. After about 7 0 00 o o to 10 days traces of rust began to form on the sample in 0 o 0. the humid environment which had been contacted with 15 N,N-diethylhydroxylamine. No rusting was observed during o 0 ao 0 the test on the sample which had been contacted with the .o hydroxylamine compound and left in an open environment.

The laboratory studies of this example confirmed field studies which had shown that entire drums which had .0.o 20 been cleaned of grease, oil, paint, chemical residues, 0o 0 *oo. etc., commonly by using caustic, could be protected by immersing them for short periods in solutions containing 0o° N,N-diethylhydroxylamine. These field studies used drums 0000 having steel surfaces which exhibited rust formation during and after the drum cleaning process unless a "o0S corrosion inhibitor was employed. Use of Sa.a64 N,N-diethylhydroxylamine alone, or in combination with sodium nitrite inhibited the formation of rust between the stages of the cleaning process and thereafter. During the studies, the N,N-diethylhydroxylamine was generally applied by immersing a drum for about 1 minute in a soak 16 901205,immdaO70,a:\36318gra.res,3

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a- -Y tank having a water temperature between about 800C and 100°C and a concentration of N,N-diethylhydroxylamine between about 1000 ppm and 3000 ppm. The treated drums I were usually passed through drying furnaces and then onto further processing steps such as drum painting.

The examples described herein include various embodiments of the invention. Other embodiments will be apparent to those skilled in the art from a consideration of the specification or practice of the invention disclosed herein. It is understood that modifications and variations may be practiced without departing from the spirit and scope of the novel concepts of this invention.

It is further understood that the invention is not 0 a0 confined to the particular formulations and examples /15 herein illustrated, but it embraces such modified forms thereof as come within the scope of the following claims.

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Claims (15)

1. A method of treating articles having surfaces of iron, mild steel, or the like to protect said surfaces from corrosion comprising the steps of cleaning the surfaces; and contacting said surfaces for a period of from 10 seconds to 1 hour with a corrosion-inhibiting dosage of an aqueous treatment containing between 0.001 and 98 percent by weight of hydroxylamine compounds having the formula: R N-OH R 2 Swhere R, and R 2 may be the same or different, and are selected from the group consisting of hydrogen, lower t alkyl optionally substituted with one or more hydroxyl or halogen groups, and aryl optionally substituted with one or more hydroxyl or halogen groups, and water soluble salts thereof. 0 0 o0 o* 2. The method of claim 1 wherein the hydroxylamine 0. compound is N,N-diethylhydroxylamine. 0 00 0 o0 0 3. The method of claim 1 or claim 2 wherein the aqueous treatment contains between 1000 ppm and 10,000 ppm of the hydroxylamine compound. 00

4. The method of any preceding claim wherein R, and R 2 ji' Iare selected from hydrogen, lower alkyl groups having between 1 and 8 carbon atoms, phenyl, benzyl and tolyl. The method of any preceding claim wherein the temperature of the aqueous treatment is between 50°C and 1000C. (4 901205,immdat070,a:\36318gra.res,18 ii I I 6 '3 1W-1 0 0 f S: i f c i t C 0 000 oe o0 o o o o o 0000 0 0 ooo 0-0 0 -19-

6. The method of any preceding claim wherein the pH of the aqueous treatment solution is between 7 and 13.

7. The method of any preceding claim wherein the surfaces are contacted with the aqueous treatment by immersing them in a solution containing said hydroxylamine compound or by spraying them with an aqueous solution containing said hydroxylamine compound.

8. The method of any one of claims 1 to 6 wherein said article is contacted with an aqueous vapor containing said hydroxylamine compound or with a condensate thereof.

9. The method of claim 8 wherein the hydroxylamine is vaporized from a solution having a ppm of between 9 and

13. An improved method of treating articles made of iron-based metals which have cleaned surfaces that are susceptible to rusting, to inhibit said rusting, the improvement comprising the step of exposing the cleaned surfaces of said articles for a period of from 10 seconds to 1 hour to an aqueous treatment containing hydroxylamine compounds having the formula: N-OH where R, and R 2 may be the same or different, and are selected from the group consisting of hydrogen, lower alkyl, and aryl, and water soluble salts thereof, in an amount, between 0.001 and 98 percent by weight, effective to facilitate the formation of a thin protective layer comprising ferriferrous oxide on said surfaces. i 00 0 0 0 0 0 00 000001 0 0 0 0 9 t «e IM 90l205,immdatO7O,a:\36318gra.res,19 qa' o C Ir"i ur~ w~Rnr r r t r c C 0t o 0 oQ o O 0000 o 0 0 0 0 0 0 11. The improved method of claim 10 wherein the hydroxylamine compound is N,N-diethylhydroxylamine. 12. The improved method of claim 10 or 11 wherein the aqueous treatment contains between 1000 ppm and 10,000 ppm of the hydroxylamine compound. 13. The improved method of any one of claims 10 to 12 wherein the lower alkyl group has between 1 and 8 carbon atoms, and the aryl is selected from the group consisting of phenyl, benzyl and tolyl.

14. The improved method of any one of claims 10 to 13 wherein the temperature of the aqueous treatment is between 10*C and 100 0 C, and the pH of the aqueous treatment is between 2 and 13.

15. The improved method of any one of claims 10 to 14 wherein the surfaces are contacted with the aqueous treatment by immersing them in a solution containing said hydroxylamine compound or by spraying them with an aqueous solution containing said hydroxylamine compound.

16. The improved method of any one of claims 10 to 14 wherein said article is contacted with an aqueous vapor containing said hydroxylamine compound or with a condensate thereof. o 0 0 0 oo aO 0 a 0 0 0 00 0 4 l 0 0 I c's

17. A method of treating a clean mild steel article to inhibit rusting and corrosion thereof comprising the step of contacting the surface of said article for a period of from 10 seconds to 1 hour and at a pressure of between 0 psig and 50 psig with an aqueous solution having a pH between 2 and 13 and a temperature between 10 0 C and 120°C and containing an effective amount, between 0.001 and 98 weight percent, of hydroxylamine compounds having the :i d i 4 B 901205immdatO7O,a:\36318grares,20 The coupons were stacked to simulate stacked steel parts 8 I; I- Irr~r~r~ l~i.U19P* rj 7--~L ii: ii :i 1 -21 formula R1 N-OH R 2 0 C 0r 4 4e 04 00 0 00 4 0 where R, and R 2 may be the same or different, and are selected from the group consisting of hydrogen, lower alkyl, and aryl, and water soluble salts thereof; and drying said article.

18. The method of claim 17 wherein the aqueous solution has a pH of at least 7, and a temperature of between and 100 0 C, and contains between 1000 ppm and 10,000 ppm of the hydroxylamine compound.

19. The method of claim 17 or 18 wherein R, and R 2 are selected from hydrogen, lower alkyl group having between 1 and 8 carbon atoms, phenyl, benzyl and tolyl.

20. The method of claim 18 wherein the hydroxylamine compound is N,N-diethylhydroxylamine.

21. A method of treating articles according to claim 1, claim 10 or claim 17, and substantially as hereinbefore described with reference to the examples. 0000 0D o 4 00 4 0 0* 0 I 0 t t (CCr DATED this 5th day of December 1990. W.R. GRACE CO.-CONN. By Its Patent Attorneys DAVIES COLLISON 901205,immdat.O7,a:\36318grares,21 ii i