MXPA00012129A - Methods of inhibiting corrosion using isomers of chloro-methylbenzotriazole - Google Patents

Abstract

The use of halo-benzotriazoles as corrosion inhibitors in aqueous systems is disclosed. Specific isomers of chloro-methylbenzotriazole were found to be more effective corrosion inhibitors than tolyltriazole in the presence of chlorine.

Description

c * METHODS FOR INHIBITING CORROSION USING CHLORINE-METHYLENE BENZOTRIAZOL ISOMERS FIELD OF THE INVENTION The present invention relates to the control of corrosion in aqueous systems More particularly, the present invention relates to the corrosion inhibition of steel and copper alloys in aqueous systems through the application of chloromethyl and lbenzotpazoles to the aqueous system.

BACKGROUND OF THE INVENTION The use of triazoles to inhibit corrosion of copper and iron alloys in a wide variety of aqueous and non-aqueous systems is well known. In industrial water cooling systems, benzotpazol and tolyltriazole are frequently used. Preferred due to its internal cost Triazoles are film-forming materials that provide efficient coverage of metal or metal oxide surfaces in a system thus providing protection against corrosive elements present in an aqueous system In addition to the tendency to form various film azoies, also precipitate soluble ions, divalent copper The - precipitation prevent the transport of copper ions to ferrous surfaces where the galvanic reactions between copper ions and iron atoms leads to the corrosion of the ferrous metal. = While the use of azoies for corrosion inhibition is extensive there are disadvantages in its use specifically with tolyltriazole The most important disadvantages are experienced when azoies are used in combination with halogen oxidizers Halogens n oxidants such as chlorine bromine elemental hypohalose acids or alkaline solutions, ie solutions of hypochlorite or hypobromite ion) are the most common materials used to control microbiological growth in cooling systems of water When copper or iron alloys that have previously been protected with azoies are exposed to an oxidizing halogen, corrosion protection is interrupted. After the interruption it is difficult to form new protective films in cooling systems treated with toliltpazole which are chlorinating particularly continuously chlorinated Very high tolyltriazole dosages are frequently applied in an effort to improve performance frequently with limited success ^ 5 Degradation of film protection *. 'j * .. ^ Ssaatv »i &A% a &js? ¡SL. *» r-i sfeCi -. - < . » - J • ^ «te '» azol in the presence of oxidative halogens is well documented in the literature. For example, R. Holm, et al. Concluded that hypochlorite penetrates an intact triazole film, leading to superior corrosion regimes, and that secondly, hypochlorite attacks the trial surface previously with film, interrupting or degrading The film (53rd Annual Meeting of the International Water Conference Paper No. IWC-92-40, 1992), Lu and colleagues also studied interactions of triazole films with hypochlorite on surfaces of copper and copper alloy ("Effects of Halogenation in Yellow Metal Corrosion: Inhibition by Triazoles ", Corrosion, 5JD, 422 (1994)). Lu. and col, concluded (a) a triazole previously formed in film on copper and brass surfaces is subjected to decomposition during chlorination; (b) the stability of the tpazol previously formed in film on copper and brass to NaOCI was improved when tolyltriazole was added to the hypochlorite solution; (c) clean copper surfaces (ie, without prior film application) did not develop good protective films when placed in solutions containing mixtures of toliltpazole and NaOCI Thus, the combination of toliltpazole with NaOCI did not produce a composition capable of efficient film formation or corrosion inhibition The nature of the reaction products when azoies are exposed to oxidant halogens in a cooling water system is not clear The literature teaches that a compound is formed when chlorine and tolyltriazole are combined in cooling waters and that it responds to analytical tests such as chlorine. For example Vanderpool, and col, you state that chlorine reacts reversibly with tolyltriazole to produce N-chloro-toliltpazole. They specifically state "probably this compound itself is not an inhibitor" rather they teach that it hydrolyzes easily to the original tpazol and hypochloric acid so that tolyltriazole Free is made available for corrosion inhibition "Improving the efficiency of Toliltpazole Corrosion Inhibitor in Presence of Chlorine and Bromine" NACE Corrosion 787. Paper No 157 (1987)) Hollander and May stated that they were able to isolate 1-chloro- tol? l tpazol of stored solutions, more highly concentrated. but they also teach that "at low concentrations (less than 20 mg / L) rapid hydrolysis made it impossible to isolate the chlorine adducts." Based on the proton NMR analysis, the isolated Hollander and May material was chloro-tolyltriazole. Another observation ... is that a very characteristic odor is present whenever tolyltriazole and chlorine are combined in cooling water. In contrast, chloro-toliltpazole does not respond to analytical tests like chlorine, despite prolonged boiling. And the chloro-tolyltriazole solutions, surprisingly. they do not produce the characteristic smell. In this manner, the chloro-tolyltriazole is clearly different from the reaction product of tolyltriazole-chlorine which is formed in situ in cooling water systems. There are also references in the literature to 5-chlorobenzotriazole (ie, CAS number [94-97-3]). In "The Water Drop", Volume 1 No. 2, 1985, Puc orius &; Associates state that chlorinated toliltpazole is effective as a corrosion inhibitor and cite R.P Carr as a reference. A work literature journal published by Carr indicates that it actually teaches that reactions between tolyltriazole and chlorine do not occur under cooling water conditions ("The Functioning of Toliltriazole in the Presence of Sodium Hypochlocide under Simulated Field Conditions", NACE Corros ? on / 83. document No. 283, 1983) U? Sfei - ^ "J- ^" In this document from Corros? On / 83, Carr discusses the action of inhibiting a chloro-azole but it is a reference to previous literature, and specifically to the action of 5-chlorobenzotpazole and azoies substituted with related aryl 5 in solutions of sulfuric acid ("Effects of Substituted Benzotpazol on the Electrochemical Copper Behavior in H? S04." Wi et al. Corrosion Volume 37, No. 4, 223 (1981)) From the 1985 Puckorius reference , there has been extensive use of 10-tolyltriazole in chlorinated cooling systems with well-established performance difficulties indicating a continuous problem, not solved in the technique. Other problems are well known when combine toliltpazole and oxidant halogens in cooling waters These include a loss in the precipitation extent of transition metal ions such as copper leading in this way to improved transport and galvanic corrosion a change in the response of the conventional spectrophotometry test for tolyl triazole, which leads to unintentional overfeeding and the objectionable odor mentioned above. This odor can be perceived even when the cooling water originally contained 1 ppm of toliltpazole or less since the water of cooling often passes through cooling towers, evaporation and scum release objectionable odor to the local environment It is believed that the odorous material is N-chloro-toliltipazole, which forms OCI reversibly with tolyltriazole in dilute solution and which is absent in the final product when the reaction is carried in concentrated solution ie tolyltriazole + OCI - > N-chloro-tolyltriazol- (intermediate) - > chloro-toliltpazole There is no evidence of reversion of chloro-tolyltriazole to either the odorous intermediate or toliltpazole. Nor is there any evidence of reactions between hypochloro and chloro-tolyl triazole in dilute aqueous solutions.

SUMMARY OF THE INVENTION The present inventors have discovered that specific isomers of chloro-methylbenzotriazole are more effective than other chloro-tolyl t-pazol isomers in inhibiting corrosion in aqueous systems. The specific chloro-methylbenzotpazole isomers are substantially more effective corrosion inhibitors than the isomers of chloro-tolyltriazole in the presence of chlorine In addition, when the specific chloro-methylbenzotpazole isomers are exposed to chlorine, no objectionable odor is formed BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a graph of corrosion rate (mpy) versus time Figure 2 is a reaction sequence for the preparation of 6-chloro-5-methylbenzotriazole Figure 3 is a reaction sequence for the Preparation of 4-chloro-5-methobenzotpal Figure 4 is a reaction sequence for the preparation of 5-chloro-4-methobenzotrolol DESCRIPTION OF THE PREFERRED MODALITIES The present inventors have discovered that specific isomers of chloro-methyl-benzotpazole are significantly more effective than other chloro-tolyl-triazole isomers in inhibiting corrosion in aqueous systems. The specific chloro-methylbenzotriazole isomers are substantially an inhibit of corrosion more effective than other isomers of chloro-tolu-1-tpazol in the presence of chlorine The effectiveness of the specific chloro-met-l-benzotpazole isomers is surprising Furthermore, the chloromethane-isotropic isomers specific in the present invention are not subject to the formation of objectionable odors when exposed to chlorine such as tolyltriazole The ex-situ preparation of 4-chloro-5-methylenebenzotpal, 5-chloro-4-methylenebenzotpazole and 6-chloro-5-methobenzotpazole was found to provide an corrosion inhibitor that exhibited surprising and unexpected activity when compared to a treatment comprising and other chloro-tolll-1-triazole isomers The results of the studies of the present invention clearly show that 4-chloro-5-methyl-benzotpal 5-chloro-4-methyl-benzotrol and 6-chloro-5-methyl L-benzotrol azol are more effective corrosion inhibiting agents than other chloro-tolyl triazole isomers. 6-Chloro-5-methylenebenzotrol can be prepared by an appropriate medium. In the following examples the 6-chloro-5- Methenylbenzotpazol was prepared through the reaction sequence set forth in the Figure The reaction sequence set forth in Figure 2 is as follows 3-chloro-4-melacelaceilide was prepared from 3-chloro-4-methylanilma via acetylation of the aniline with acetic anhydride in a solution of aqueous methanol. The mixture of chloro-methylene isomers, troacetanilide, was then formed by nitration of the acetanide with sulfuric and nitric acid. The desired isomer (3-chloro-4-methyl-6-m-troacetanilide) was purified through recrystallization. of ethanol. 3-Chloro-4-met. 6-n? Troamlma through deprotection of acetanilide with hydroxide and potassium in an ethanol solution The reduction of nitros groups in 3-chloro-4-met? L-6-n? Troaniline was achieved with zinc dust in ethanol 6-chloro-5-methyl-benzotpazole was formed by reaction of 4-chloro-5-methyl-1, 2-benzene-d-amine with sodium nitrite and acid Acetic acid 4-Chloro-5-methobenzotnazole can be prepared by any appropriate means In the following examples, 4-chloro-5-methobenzotpazole was prepared through the reaction sequence set forth in Figure 3. The reaction set forth in Figure 3 is as follows: 3-chloro-4-met-1-acetamide was prepared from 3-chloro-4-met? lanilma through acetylation with the aniline with acetic anhydride in an aqueous methanol solution A mixture of chloromethyl-methylnitroacetanilide isomers was then formed by nitration of the acetanilide with sulfuric and nitric acid The desired isomer (3-chloro-4-methoxy) -2-m troanilide) was purified via rectalisation of ethanol. 3-Chloro-4-methyl-2-n-troanol was prepared by deprotection of acetamide with potassium hydroxide in an ethanol solution. of the nitros groups in the 3-chloro-4-met? l-2-m troanilma was achieved with zinc powder in ethanol 1 4-chloro-5-met? lbenzotpazol was formed by reaction of 3-chloro-4-met ? ll, 2-benzene-diamine with sodium nitrite in acetic acid 5-chloro-4-met? lbenzotpazole can be prepared by any appropriate means In the following examples 5-chloro-4-met? lbenzotpazole was prepared through the reaction sequence set forth in Figure 4 The reaction sequence set forth in Figure 4 is as follows 3-chloro-2-methylacetanilide was prepared from 3-chloro-2-methylamine 1 through acetylation of the aniline with acetic anhydride in an aqueous solution of methanol A mixture of chloromethane isomers The 1-nitro-acetam-1-ida was then formed by nitration of the acetanilide with sulfuric and nitric acid The 3-chloro-2-methyl-4-n-th isomer was removed by precipitation after addition of potassium hydroxide to the mixture of isomer in ethanol 3-chloro-2-met i 1-6-n? troacetan? The mixture was heated to reflux in an aqueous solution of sodium hydroxide. The solid that formed was 3-chloro-2-meth? -6-n? Troan? Lma. The reaction with a solution of stannous chloride in hydrochloric acid provided an precipitate of 4-chloro-3-met? ll-2-benzene? amma The reaction with sodium nitrite in acetic acid yielded a solid 5-chloro-4-methylbenzotpazol. In treating an aqueous system according to the present invention, the -chloro-5-methobenzotnazole 4-chloro-5-methyl-benzotpazole or 5-chloro-4-methobenzotrolol is preferably continuously fed into the water. A preferred treatment concentration ranges from about 0 2 to 10. parts per million However, continuous feeding is not a requirement The chloro-met-l-benzotpazole isomers are can feed at a sufficient concentration to form a protective film and then the feed can be discontinued for prolonged periods of time.

The chloro-methylenebenzotriazole of the present invention can be used in combination with other corrosion inhibition and / or deposit treatments known in the art including, but not limited to, phosphonates, homo- and acrylic chelating copolymers and copolymers.

Oximes The present invention will now be further described with reference to a number of specific examples that should be considered only as illustrative and not as restricting the scope of the invention. present invention EXAMPLE 1 The corrosion inhibiting activity of the treatment of the present invention was evaluated using a Picudo Weakness Corrosion Test Apparatus (BCTA). The BCTA consists of a weighted beaker equipped with an a? Re / C02 spray, an electrochemical probe of copper and a magnetic stirrer da The test solution was 1 9 liters Spraying A? re / C02 is continuous during the test The reference electrode and the counter electrode are constructed of Hastelloy C22 The beaker is immersed in a bath water for temperature control Electrochemical corrosion data were obtained periodically in the probe during the test using a polarization resistance technique All tests were conducted at 49QC (120SF) using a shaking regime of 400 RPM For all tests a water consisting of 500 ppm of Ca (as CaCO3), 250 ppm of Mg (as CaCO3) 354 ppm of chloride, and 240 ppm of sulfate was used The pH of the system was 7 2 with the corresponding "M" alkalinities being 15 ppm as CaC03 The following treatments were also used in the aqueous system 15 ppm porto-P04 (P04) 3 ppm of P207 (as P04), and lOOm of HPS-1 (a copolymer of acrylic acid and sodium salt of the hydroxypropyl sulfonate ether The test method was designed to evaluate the chloro-toliltpazoles for copper corrosion inhibition ba or halogenation. The copper probes were immersed in the test water containing various azole isomers for approximately 15 hours. stabilized bleaching solutions (NaOCI, the chlorine source) were batch-fed to the test water Tests were continued for another 25 sheets Copper corrosion rates were measured periodically during the 40-hour test or changes in corrosion regimes after fed with bleach were used as an indicator of the effectiveness of the various azoies under chlorination Table 1 and Figure 1 summarize the results for toliltpazole and various treatments of chloro-tolyl tpazol isomer at 3 ppm active Table 1 Average Copper Corrosion Regime Regime Corrosion Regime Average to Average Corrosion to Samples 0 to 15 hours 16 to 40 hours (mpy) (py) 3 ppm Toliltpazole 0 0179 2 3688 3 ppm 4-Chloro-5- methylbenzotpazol 0 0113 0 649 3 ppm 6-chloro-5-ethylbenzotriazole 0 0122 0 0469 3 ppm 5-chloro-4-methylbenzotriazole 0 009 0 4853 3 ppm 7-chloro-4- 0 0177 4 3564 metlbenzotpazol As you can see from the results all the azoies gave excellent protection against copper corrosion without the presence of chlorine. The average corrosion regimes during the first 15 hours are less than 0 02 mpy and as shown in Table 1 after the feeding of load of 2.5 ppm NaOCI dramatic increases in copper corrosion rates were observed in the water treated with toliltpazole The slight increases in corrosion rate for 4-chloro-5-methylbenzotpazole and 5-chloro-4-meth i lbenzotriazole can seen in Figure 1 while that the copper corrosion regime for water treated with 6-chloro-5-methylbenzotpazole remained essentially unchanged Even though this invention has been skewed with respect to particular embodiments thereof, it is evident that numerous other forms and modifications of this invention will be apparent to those skilled in the art The appended claims and this invention should generally be considered to cover all of these obvious forms and modifications that are within the true spirit and scope of the present invention. fifteen twenty iBJjhg- •• »». »> . z ^ s-'i ^^. ^. ^ ..,

Claims (25)

1 - . 1 - A method to inhibit the corrosion of metal surfaces by an aqueous system that is 5 treats with a halogen comprising adding to the aqueous system being treated with a halogen an effective amount for the purpose of inhibiting the corrosion of 6-chloro-5-methobenzotpazole

2 - The method according to claim 1 wherein the 6-chloro-5-methylbenzotriazole is added to the aqueous system at a concentration greater than about 0.2 parts per million

3 - The method according to claim 1, wherein the 6-chloro-5-methyl-1-benzotriazole is added to the aqueous system at a concentration of about 0 2 parts per million to about 10 parts per million

4 - The method for forming a corrosion inhibition layer on a metal surface in -0 contact with an aqueous system which is being treated with a halogen comprising adding to the aqueous system which is being treated with a halogen an effective amount for the purpose of inhibiting the corrosion of 6-chloro-

5-methyl-benzotpazol 5 - A method for reducing the chlorine demand in an aqueous system that is being treated with chlorine to inhibit microbiological growth which comprises adding to the aqueous system an effective amount for the purpose of reducing the chlorine demand of

6-chloro-5-methylbenzotnazole. A method for inhibiting the transport of copper ion in an aqueous system that is being treated with a halogen in contact with metal surfaces including copper which comprises adding to the aqueous system an effective amount for the purpose of 6-chloro-5-met íl-benzotpazol

7 - A method to inhibit corrosion of metal surfaces contacted with an aqueous system that is being treated with a halogen that comprises adding to The aqueous system which is being treated with a halogen is an effective amount for the purpose of inhibiting the corrosion of 6-chloro-5-meth i lbenzotriazole in combination with at least one other aqueous system treatment material

8 - The method according to claim 7 wherein the other aqueous system treatment material comprises corrosion inhibition treatments, deposit inhibition treatments and mixtures thereof

9 - The method according to claim 7, wherein the treatments of corrosion inhibition treatments deposit inhibition and mixtures thereof include phosphates, phosphonates, acrylic homopolymers, acrylic copolymers, oximes chelating agents, biocides and mixtures thereof.

10 - A method for inhibiting corrosion of metal surfaces contacted with an aqueous system being treated. with a halogen, which comprises adding to the aqueous system that is being treated with a hal An effective amount for the purpose of inhibiting the corrosion of 4-chloro-5-methyl-benzotrol azol. The method according to claim 10, wherein the 4-chloro-5-methyl-benzotpazole is added. to the aqueous system at a concentration greater than about 0 2 parts per thousand ion 12 - The method according to claim 10 wherein the 4-chloro-5-met l-benzotpazole is added to the aqueous system at a concentration of about 0 2. parts per million to about 10 parts per million 13 - A method for forming a corrosion inhibiting layer on a metal surface in contact with an aqueous system that is being treated with a halogen, which comprises adding to the aqueous system that 7 is being treated with a halogen, an effective amount for the purpose of corrosion inhibition of 4-chloro-5-methyl libenzotriazole 14 - A method to reduce the chlorine demand in an aqueous system that is being treated with chlorine to inhibit the microbiological growth comprising adding to the aqueous system an effective amount for the purpose of reducing the chlorine demand of 4-chloro-5-methylbenzotpazole 15 - A method for inhibiting copper ion transport in an aqueous system that is being treated with a halogen in contact with metal surfaces including copper comprising adding to the aqueous system an effective amount for the purpose of 4-chloro-5-methyl-benzotpazole 16 - A method for inhibiting corrosion of metal surfaces contacted with an aqueous system that you are dealing with a halogen that comprises adding to the aqueous system that is being treated with a halogen, an effective amount for the purpose of inhibiting the corrosion of 4-chloro-5-met-l-benzotrol azol in combination with at least one other aqueous system treatment material 17 - The method according to claim 16, wherein the Another aqueous system treatment material comprises treatments of ^^^ f corrosion inhibition, deposit inhibition treatments, and mixtures thereof 18 - The method according to claim 16, wherein the corrosion inhibition treatments, deposit inhibition treatments, and mixtures of the same comprises phosphates phosphonates, acrylic homopolymers, acrylic copolymers, chelants, oximes, biocides and mixtures thereof. 19 - A method for inhibiting corrosion of metal surfaces contacted with an aqueous system that is being treated with a halogen comprising adding to the aqueous system being treated with a halogen, an effective amount for the purpose of inhibiting the corrosion of 5-chloro-4-met-l-benzotnazole 20 - The method according to claim 19, wherein the 5-chloro-4 -met? l-benzotriazole is added to the aqueous system at a concentration greater than about 0 2 parts per million 21 - The method according to claim 19 n where 5-chloro-4-met? 1-benzotpazole is added to the aqueous system at a concentration of about 0 2 parts per million to about 10 parts per million .A »S» a, in. &,. .... - ^. t,. í ~,. > A «« ^ - S.% sa8, -6- 22 - A method for forming a corrosion inhibition layer on a metal surface in contact with an aqueous system which is being treated with a halogen, which comprises adding to the system water that is being treated with a halogen, an effective amount for the purpose of inhibiting the corrosion of 5-chloro-4-meth i 1-benzotriazole 23 - A method to reduce the chlorine demand in an aqueous system that is being treated with chlorine for inhibit microbiological growth comprising adding to the aqueous system an effective amount for the purpose of reducing the chlorine demand of 5-chloro-4-methylbenzotpazole 24 - A method for inhibiting the transport of copper ion in an aqueous system being treated with a halogen in contact with metal surfaces including copper comprising adding to the aqueous system an effective amount for the purpose of 5-chloro-4-methobenzotrol azol 25 - A method for inhibiting surface corrosion metal cores contacted with an aqueous system which is being treated with a halogen, which comprises adding to the aqueous system which is being treated with a halogen an effective amount for the purpose of inhibiting the corrosion of 5-chloro-4-met? lbenzotpazol in Ftv v, - '^^ •• ^^^ • ^ > ) t > ^^ g > ^^^ "ji, a--". ^ 8, - ,, jt U "ábM combination with at least other aqueous system treatment material. 26. The mét «áßb according to claim 25, wherein the other aqueous system treatment material comprises corrosion inhibition treatments, deposit inhibition treatments, and mixtures thereof. 27. The method according to claim 25, wherein the corrosion inhibition treatments, deposition inhibition treatments, and mixtures thereof include phosphates, phosphonates, acrylic homopolymers, acrylic copolymers, chelants, oximes, biocides and mixtures. thereof . ^ Mz áÉÉks &MSzmX: 7"; ' fc 'Sfes, - jata-jfe' & ss'.fc-j »