Method for inhibiting corrosion of ferrous metals with 1-hydroxybenzotriazoles

Abstract

A corrosion inhibiting composition which comprises an aqueous medium having dissolved therein an effective amount of at least one of water-soluble 1-hydroxybenzotriazole compounds and water-soluble salts thereof, said water-soluble 1-hydroxybenzotriazole compound having the formula of ##SPC1## Wherein X and Y are respectively one member of the group consisting of hydrogen atom, a lower alkyl group having 1 to 3 carbon atoms, nitro group, halogen atom, sulfo group, methoxy group, carboxy group and cyano group.

Description

This invention relates to an aqueous corrosion inhibiting composition and a method for inhibiting corrosion of ferrous metals, such as iron, steel and iron alloys.

In the prior art sodium nitrate and amine-based surfactants are known as water-soluble corrosion inhibitors and have been extensively used for protecting ferrous metals from corrosion. However, such known inhibitors are not sufficient in practical uses. Although sodium nitrate displays an excellent corrosion inhibiting effect on ferrous metals which are brought into contact with water having dissolved therein said inhibitor, for example, the effect reduces markedly when ferrous metals coated with the inhibitor is placed in the air. Further, the nitrite has a considerable toxicity, causing water pollution when exhausted to water system without post-treatment. Amine-based surfactants are insufficient in corrosion inhibiting effect in air as well as in water and will sometimes disturb cooling and washing operations due to marked foamability thereof. Ferrous metals treated with the amine-based surfactants, moreover, can not be subjected to parkerizing treatment or coated with paints without removing the surfactants attached thereto. When the surfactants are to be removed, a complicated procedure such as electrolysis is necessary, since it can not be washed off with an alkali solution.

An object of the invention is to provide a composition and method for inhibiting corrosion of ferrous metals which are free from the drawbacks of the conventional inhibitors.

Another object of the invention is to provide a corrosion inhibiting composition which displays an excellent corrosion inhibiting effect on ferrous metals not only in water but also in air.

Another object of the invention is to provide a corrosion inhibiting composition which is low in toxicity and can be exhausted free from water pollution.

Another object of the invention is to provide a corrosion inhibiting composition which has no foamability and therefore can be added to cooling or washing water without adversely affecting cooling or washing operation.

Another object of the invention is to provide a corrosion inhibiting composition which makes it possible to directly subject ferrous metals treated therewith to parkerizing treatment or coating with paints.

Another object of the invention is to provide a corrosion inhibiting composition which can be easily removed from the surface of ferrous metals treated therewith, as desired.

These and other objects of the present invention will be apparent from the following description.

The corrosion inhibiting composition of the present invention comprises an aqueous medium having dissolved therein an effective amount of at least one of water-soluble 1-hydroxybenzotriazole compounds and watersoluble salts thereof, said water-soluble 1-hydroxybenzotriazole compound having the formula of ##SPC2##

wherein X and Y are respectively one member of the group consisting of hydrogen atom, a lower alkyl group having 1 to 3 carbon atoms, nitro group, halogen atom, sulfo group, methoxy group, carboxy group and cyano group; preferable X and Y being hydrogen atom, a lower alkyl group having 1 to 3 carbon atoms or nitro group.

According to the researches of the present inventors it has been found that when ferrous metals are treated with the 1-hydroxybenzotriazole and its derivatives specified above, they are effectively protected from corrosion not only in water but also in air. Such effect can not be expected from benzotriazole per se, as known in the art, which displays a corrosion inhibiting effect only on copper and its alloys but little or no effect on ferrous metals. The reason why the 1-hydroxybenzotriazole and its derivatives can display such marked effect on ferrous metals has not been made clear yet, but is supposedly attributable to the fact that the surface of ferrous metals is covered with a monomolecular film of chelate compound formed between iron atom and 1-hydroxybenzotriazole or its derivatives to be shut off from air and/or water, whereby the ferrous metals are effectively protected from corrosion.

Moreover, ferrous metals treated with the present composition can advantageously be subjected to parkerizing treatment or coated with paint without removal of 1-hydroxybenzotriazole or its derivatives therefrom. When ferrous metals treated with the present composition are to be chemically or electrically plated, 1-hydroxybenzotriazole or its derivatives attached thereto can easily be removed from the metal surface by simple procedures, for example, by washing with an alkali solution.

The 1-hydroxybenzotriazole and derivatives thereof to be used in the invention are 1-hydroxybenzotriazole compounds having the formula (I) before and water-soluble salts thereof. Representative examples of the 1-hydroxybenzotriazole compounds are 1-hydroxybenzotriazole, 1-hydroxy-4-methyl-benzotriazole, 1-hydroxy-6-nitro-benzotriazole, 1-hydroxy-5-chloro-benzotriazole, 1-hydroxy-6-sulfo-benzotriazole, 1-hydroxy-5-methoxy-benzotriazole, 1-hydroxy-5-cyano-6methyl-benzotriazole, 1-hydroxy-6-carboxy-benzotriazole , 1-hydroxy-5-isopropyl-benzotriazole, etc. Also employable in the invention are water-soluble salts of the above 1-hydroxybenzotriazole compounds. Such salts include, for example, ammonium salts, alkali metal salts, hydrazine salts and amine salts.

In the invention it is preferable to use the water-soluble salts, since they have no acidity and display higher water-solubility. Such salts can easily be prepared by adding ammonia, alkali metal hdyroxides, hydrazines or amines to an aqueous solution of 1-hydroxybenzotriazole compounds to produce the solution having a pH adjusted. Employable amines include various amines capable of producing water-soluble salts by the reaction with the 1-hydroxybenzotriazoles. Examples thereof are alkanol amines such as monoethanolamine, diethanolamine, etc., alkylamines such as ethylenediamine, propylenediamine, dicyclohexylamine, etc.

Of the above 1-hydroxybenzotriazole and derivatives thereof preferable are 1-hydroxybenzotriazole, 1-hydroxy4-methyl-benzotriazole, 1-hydroxy-6-nitrobenzotriazole and water-soluble salts thereof.

The 1-hydyroxybenzotriazole compounds to be used in the invention are known in the art and can be prepared, for example by the reaction of hydrazine with o-chloronitrobenzene having or not having one or two substituents.

Ferrous metals to which the present composition is applied include iron and its alloys such as carbon steel, mild steel, stainless steel, cast iron, etc.

The 1-hydroxybenzotriazole and derivatives thereof to be used as corrosion inhibitor in the invention are water-soluble, so that they can be applied to the ferrous metals in the manner conventional to water-soluble corrosion inhibitors. For example, ferrous metals may be brought into contact with the present corrosion inhibitor by coating them with an aqueous solution of the inhibitor, followed by drying, or by adding the inhibitor to water to be brought into contact with the ferrous metals. In the latter case, the present inhibitor is added to water such as cooling water in the rolling of ferrous metals, cooling water in a cooling system, washing water for pickled or degreased ferrous metals, etc. Since the present inhibitor is thermally stable, it displays an excellent corrosion inhibiting effect in various temperature conditions, for example, in primary cooling water of near 0.degree.C in winter as well as in cooling water of about 60.degree. to 80.degree.C in rolling operation.

The effective concentration of the present inhibitor varies over a wide range depending on the application method, kind of ferrous metals to be treated, etc., but it displays a sufficient effect in such a small concentration as 0.05 wt.%. Since the present inhibitor has little or no toxicity, it can be used in any large amount. But it is preferable to use the inhibitor in a concentration of 0.05 to 10 weight percent from economical view point. Particularly, when the present inhibitor is used in the form of an aqueous solution for coating ferrous metals, preferable concentration of the inhibitor in solution is in the range of 0.5 to 5 weight percent. When the present inhibitor is added to water with which ferrous metals are brought into constant, preferable concentration thereof in the water system is in the range of 0.05 to 1.0 weight percent.

Various additives can be added to the present composition in order to improve the properties thereof. For example, water-soluble high molecular weight substances are added thereto to further improve the corrosion inhibiting effect on ferrous metals. Examples thereof are polyvinyl alcohol, polyvinyl pyrrolidone, carboxymethyl cellulose, starch, polyacrylic acid, styrene-maleic acid copolymer, etc. Further, surfactants are added in order to improve wettability of ferrous metals to be treated with the present composition. Examples of such surfactants are nonionic surfactants such as polyoxyethylene alkylphenyl ether, polyoxyethylene lauryl ether, polyoxyethylene oleyl ether, polyoxyethylene nonylphenyl ether, etc.; cationic surfactants such as quaternary ammonium salts, etc.; anionic surfactants such as ammonium salt of alkylbenzenesulfonate, sodium salt of polyoxyethylene nonylphenyl ether sulfate, etc.

For a better understanding of the present invention examples are given below.

EXAMPLE 1

Various amounts of 1-hydroxybenzotriazoles shown in Table 1 below were respectively dissolved in water at 60.degree.C, and the resulting solutions were adjusted with monoethanolamine to a pH of 7.5 to prepare compositions having varying concentrations according to this invention.

Corrosion inhibition test and toxicity test were conducted using the compositions thus obtained.

I. Humidity Cabinet Test

Cold-rolled steel sheets (JIS-G-3141, Class 1), each measuring 60 mm .times. 80 mm .times. 1.2 mm, were polished by polishing paper (JIS-R-6252, No. E240), washed with kerosene at 50.degree.C and further with methanol at 50.degree.C. The resulting steel sheets were then immersed in the abovementioned compositions for 30 seconds respectively, dried and thereafter placed in humidity cabinets according to JIS-Z-0228 to inspect corrosion produced in predetermined periods of time. The results are given in Table 1 which also shows the results of treatments likewise conducted using a 1 wt.% aqueous solution of sodium nitrite as sample No. 6 and water as sample No. 7 respectively.

Table 1 __________________________________________________________________________ Sample Corrosion inhibitor used Corrosion.sup.1) No. 24 72 120 168 240 hrs. hrs. hrs. hrs. hrs. X Y Amount used (wt. %) __________________________________________________________________________ 1 --H --H 0.5 A A B C D 2 " " 1.0 A A A A B 3 " " 5.0 A A A A A 4 4--CH.sub.3 " 1.0 A A C C E 5 " 6--NO.sub.2 1.0 A A A B C (Sodium -- -- -- C E -- -- -- nitrate) 7 (Water) -- -- -- E -- -- -- -- __________________________________________________________________________ Note: .sup.1) The resulting corrosion was evaluated according to JIS-Z-2912 based on the following criteria: Symbol Degree of corrosion (%) __________________________________________________________________________ A 0 B 1 - 10 C 11 - 25 D 26 - 50 E 51 - 100 __________________________________________________________________________

II. Indoor Weathering Test

Various test pieces shown in Table 2 were polished and washed in the same manner as in test (I) and then immersed in the present compositions having varying concentrations for 30 seconds. The test pieces thus treated were suspended indoors at a temperature of 25.degree.C and humidity of 70%. The resulting corrosion was measured according to JIS-Z-2912 upon lapse of predetermined periods of time. The results are listed in Table 2, which also shows the results obtained by using a 1 wt.% aqueous solution of sodium nitrite as sample No. 20 and water as sample No. 21 respectively.

Table 2 __________________________________________________________________________ Sample Test piece Corrosion inhibitor used Corrosion.sup.1) No. 24 72 120 168 240 360 hrs. hrs. hrs. hrs. hrs. hrs. X Y Amount used (wt.%) __________________________________________________________________________ 8 CRS.sup.2) --H --H 0.5 A A A A B C 9 " " " 1.0 A A A A A A 10 " " " 3.0 A A A A A A 11 HRS.sup.3) " " 1.0 A A A A A A 12 " 4--CH.sub.3 " 1.0 A A A A B C 13 " 5--Cl " " A A A A B D 14 " --H 6--SO.sub.3 H " A A A C E -- 15 " " 6--NO.sub.2 " A A A A A A 16 CI.sup.4) 5--OCH.sub.3 --H " A A B B C C 17 CI.sup.4) 5--CN 6--CH.sub.3 1.0 A A A A B B 18 " --H 6-COOH " A A A B B B CH.sub.3 19 " CH-.angle.CH.phi. --H " A A B B C E CH.sub.3 20 CRS.sup.2) -- -- -- A B D E -- -- 21 (Water) " -- -- -- B E -- -- -- -- __________________________________________________________________________ Note:- .sup.1) Criteria of corrosion are the same as in test (I). .sup.2) CRS is cold-rolled steel of JIS-G-3141, Class 1, measuring 60 mm .times. 80 mm .times. 1.2 mm. .sup.3) HRS is hot-rolled steel of JIS-G-3131, measuring 60 mm .times. 80 mm .times. 8 mm. .sup.4) CI is cast iron of JIS-G-5501, Class 3, measuring 60 mm .times. 8 mm .times. 5 mm.

The results of the tests (I) and (II) indicate that the compositions of this invention exhibit outstanding corrosion inhibiting effects on steel and iron.

III. LD.sub.50 Test

The test was conducted using male Wistar rats after 24 hours' fasting weighing 150 g, each 10 rats as a group. An aqueous solution containing 25% by weight of 1-hydroxybenzotriazole ammonium salt ##SPC3##

was forcible administered orally to the rats and the rats were raised for 1 week in a constant temperature and constant humidity chamber at a temperature of 22.degree.C and humidity of 65%. The LD.sub.50 as determined by Litchfield Wilcoxon method was 16,330 mg/kg which is about 1/180 the LD.sub.50 of 85 mg/kg for sodium nitrile as determined in rats. This indicates that the present composition is very low in toxicity.

IV. Acute Toxicity Test

1-hydroxybenzotriazole was dissolved in water at varying concentrations, and ten killifishes measuring 2.5 to 3 cm in length were placed into each solution and raised for 24 hours. The median tolerance limit (TLm) as determined according to JIS-K-0102 was about 800 p.p.m. The TLm for sodium nitrite as determined by the same procedure was 10 to 13 p.p.m. This shows that the present compositions were very low in toxicity to fishes and almost free of water pollution.

EXAMPLE 2

1-hydroxybenzotriazole was dissolved in water at room temperature, at varying concentrations and the solutions were adjusted to pH of 8 with NaOH to prepare compositions of this invention.

Containers of cold-rolled steel sheet (JIS-G-3141, Class 1) polished and washed on the inner surface thereof in the same manner as in Example 1 (I) were filled with the compositions thus prepared and sealed. Corrosion produced in the inner surface of the container was measured upon lapse of predetermined periods of time according to JIS-Z-2912, with the results given in Table 3, which also shows the results obtained without using a corrosion inhibitor. Criteria of corrosion are the same as in test (I) of Example 1.

Table 3 __________________________________________________________________________ Sample Concen- Corrosion No. tration 24 48 72 96 120 240 360 480 (wt.%) hrs. hrs. hrs. hrs. hrs. hrs. hrs. hrs. __________________________________________________________________________ 22 0.03 A A A B B B B B 23 0.1 A A A A A A A A 24 0.3 A A A A A A A A 25 -- E -- -- -- -- -- -- -- (Water) __________________________________________________________________________

Table 3 above indicates that the present compositions are very effective in inhibiting corrosion in the surface of ferrous alloy in contact with still water.

EXAMPLE 3

A steel tube (JIS-G-3452), 300 cm in length and 4.16 cm in inner diameter, was washed with 5 wt.% acetic acid and then with water. The same composition as Sample No. 23 in Example 2 was circulated continuously through the steel tube, and the resulting corrosion was inspected upon lapse of predetermined periods of time. The results are given in Table 4.

Table 4 ______________________________________ Sample Concen- Corrosion No. tration 24 120 240 360 480 600 (wt.%) hrs. hrs. hrs. hrs. hrs. hrs. ______________________________________ 26 0.1 A A A A A A ______________________________________ Note: Criteria of corrosion is the same as in test (I) of Example 1.

Table 4 shows that the present composition is very effective in inhibiting corrosion in the surface of ferrous alloy in contact with circulating water. What we claim is: 1. A method for inhibiting corrosion of a ferrous metal which comprises contacting a ferrous metal with a composition containing an effective amount of at least one of watersoluble 1-hydroxybenzotriazole compounds and water-soluble salts thereof, said water-soluble 1-hydroxybenzotriazole compound having the formula: ##SPC4##

wherein X and Y are each respectively one member selected from the group consisting of hydrogen atom, a lower alkyl group having 1 to 3 carbon atoms, nitro group, halogen atom, sulfo group, methody group, carboxy group and cyano group. 2. The method for inhibiting corrosion of a ferrous metal according to claim 1, wherein said X and Y are respectively one member selected from the group consisting of hydrogen atom, a lower alkyl group 1 to 3 carbon atoms and nitro group. 3. The method for inhibiting corrosion of a ferrous metal according to claim 1, wherein said benzotriazole compound is at least one of 1-hydroxybenzotriazole, 1-hydroxy-4-methylbenzotriazole, 1-hydroxy-6-nitro-benzotriazole, 1-hydroxy-5-chloro-benzotriazole, 1-hydroxy-6-sulfo-benzotriazole, 1-hydroxy-5-methoxy-benzotriazole,1-hydroxy-5-cyano-6-methyl-benzotriazole , 1-hydroxy-6-carboxy-benzotriazole and 1-hydroxy-5-isopropylbenzotriazole. 4. The method for inhibiting corrosion of a ferrous metal according to claim 3, wherein said benzotriazole compound is at least one of 1-hydroxybenzotriazole,1-hydroxy-4-methylbenzotriazole and 1-hydroxy-6-nitro-benzotriazole. 5. The method for inhibiting corrosion of a ferrous metal according to claim 1, wherein said effective amount is at least 0.05 wt.% in concentration. 6. The method of inhibiting corrosion of a ferrous metal according to claim 5, wherein said effective amount is in the range of 0.05 to 10 wt.% in concentration. 7. A ferrous metal treated for resistance to corrosion, said resistance to corrosion resulting from the application to said ferrous metal of a corrosion inhibiting composition containing at least one of water-soluble 1-hydroxybenzotriazole compounds and water-soluble salts thereof, said water-soluble 1-hydroxybenzotriazole compound having the formula of: ##SPC5##

wherein X and Y are respectively one member of the group consisting of hydrogen atom, a lower alkyl group having 1 to 3 carbons, nitro group, halogen atom, sulfo group, methoxy group, carboxy-group and cyano group.

Claims

What we claim is:

1. A method for inhibiting corrosion of a ferrous metal which comprises contacting a ferrous metal with a composition containing an effective amount of at least one of watersoluble 1-hydroxybenzotriazole compounds and water-soluble salts thereof, said water-soluble 1-hydroxybenzotriazole compound having the formula: ##SPC6##

wherein X and Y are each respectively one member selected from the group consisting of hydrogen atom, a lower alkyl group having 1 to 3 carbon atoms, nitro group, halogen atom, sulfo group, methody group, carboxy group and cyano group.

2. The method for inhibiting corrosion of a ferrous metal according to claim 1, wherein said X and Y are respectively one member selected from the group consisting of hydrogen atom, a lower alkyl group 1 to 3 carbon atoms and nitro group.

3. The method for inhibiting corrosion of a ferrous metal according to claim 1, wherein said benzotriazole compound is at least one of 1-hydroxybenzotriazole, 1-hydroxy-4-methylbenzotriazole, 1-hydroxy-6-nitro-benzotriazole, 1-hydroxy-5-chloro-benzotriazole, 1-hydroxy-6-sulfo-benzotriazole, 1-hydroxy-5-methoxy-benzotriazole,1-hydroxy-5-cyano-6-methyl-benzotriazole , 1-hydroxy-6-carboxy-benzotriazole and 1-hydroxy-5-isopropylbenzotriazole.

4. The method for inhibiting corrosion of a ferrous metal according to claim 3, wherein said benzotriazole compound is at least one of 1-hydroxybenzotriazole,1-hydroxy-4-methylbenzotriazole and 1-hydroxy-6-nitro-benzotriazole.

5. The method for inhibiting corrosion of a ferrous metal according to claim 1, wherein said effective amount is at least 0.05 wt.% in concentration.

6. The method of inhibiting corrosion of a ferrous metal according to claim 5, wherein said effective amount is in the range of 0.05 to 10 wt.% in concentration.

7. A ferrous metal treated for resistance to corrosion, said resistance to corrosion resulting from the application to said ferrous metal of a corrosion inhibiting composition containing at least one of water-soluble 1-hydroxybenzotriazole compounds and water-soluble salts thereof, said water-soluble 1-hydroxybenzotriazole compound having the formula of: ##SPC7##

wherein X and Y are respectively one member of the group consisting of hydrogen atom, a lower alkyl group having 1 to 3 carbons, nitro group, halogen atom, sulfo group, methoxy group, carboxy-group and cyano group.