NZ212126A

NZ212126A - Copper-corrosion inhibitor composition and use in water cooling systems

Info

Publication number: NZ212126A
Application number: NZ212126A
Authority: NZ
Inventors: O Hollander
Original assignee: Betz Int
Priority date: 1984-06-26
Filing date: 1985-05-20
Publication date: 1988-05-30
Also published as: AU4319385A; AU582750B2; KR920002412B1; KR860000416A; EP0173427A2; JPS6156288A; IN164301B; EP0173427A3

Description

<div class="application article clearfix" id="description"> 2 12126 PnaiL, Cilufsj: Complete Specification Filed: £.5" Class: ...C22fr/.l/fty Publication Dare: P MAY 1988 j P.O. Jc."n;ii, ,\o: ... ./Jot . NEW ZEALAND PATENTS ACT, 195J No.: >V f; o ' \\ -4 > y (p llO t Date: COMPLETE SPECIFICATION \ */ COPPER CORROSION INHIBITORS AND THEIR USE IN COOLING WATER SYSTEMS XtyWe, BETZ INTERNATIONAL, INC., a corporation organised and existing under the laws of the State of Pennsylvania of 4636 Somerton Road, Trevose, in the State of Pennsylvania 19047, United States of America, hereby declare the invention for which ^ / we pray that a patent may be granted to nooe/us, and the method by which it is to be performed, to be particularly described in and by the following statement: - . 1 . (followed by Page IA) 21212G -u- e © COPPER CORROSION INHIBITORS AND THEIR USE IN COOLING WATER SYSTEMS BACKGROUND OF THE INVENTION The use of benzotriazole as corrosion or tarnish or staining " ' inhibitors for copper and copper alloys is well known. In addition 5 to the use of this compound for aesthetic purposes, it together with tolyltriazole have found widespread use in the water treatment industry and in particular in the cooling water industry. f As indicated in the BETZ HANDBOOK OF INDUSTRIAL WATER j "CONDITIONING, 1980, Belz Laboratories, Inc., Trevose, PA, pp 4; ~~—————— * ' 10 202-231, corrosion and deposit control treatments are always necessary to assure the economical and continued operations of cooling water systems, whether the systems be open,.recirculating or closed. On pages 207 through 209, many individual corrosion inhibitors, as well as combination systems, are discussed including ^ 15 the well known chromate; phosphate, zinc inhibitors, Dianodic® and Dianodic II®treatments. However, as the last paragraph on page 208 of the Handbook indicates, if copper or copper alloys are * present in the structural parts of the cooling water system, and these parts are contacted by the cooling water, copper corrosion 20 inhibitors must necessarily be included. U.S. Patents 3,837,803 and 3,960,576 arid NZ Patent Specification No. 193766 provide illustrations as to the type corrosion inhibitors ccrrmonly used in conjunction with basic ferrous metal inhiKTEors and/or canoositions. 'o ^ On / 20 JAN 1988 SI 12126 -2- As established by the above references, mercaptobenzothiazole as well as certain other thiazoles, and benzotriazole and derivatives thereof, primarily tolyltriazole, have found widespread use. As is apparent, the water treatment industry is continually evaluating 5 additional compounds in an attempt to discover more effective, more economical, more easily applied treatments, and a significant part W of this effort is the development of copper inhibitors. While these inhibitors are in fact significant in the water treatment industry, they are also important in general use for inhibiting the staining 10 and/or tarnishing of items such as decorative pieces, pots, structural parts of lamps, etc. which are'fabricated from copper or copper containing alloys. As is well known, items such as the decorative pieces, when exposed to even a slightly humid atmosphere, tarnish or stain. Accordingly, that industry is also looking for 15 ways to avoid the problem. Present Invention The present inventor has discovered that the application of a compound comprising the formula wherein R is a linear or branched, substituted or unsubstituted, 25 hydrocarbon group containing 3 to about 8, and preferably 4 to 6, carbon atoms to a non-ferrous metal surface, and in particular copper or copper containing surfaces, will promote corrosion 212126 o o -3- protection as well as tarnish and stain resistance. Of particular interest in this regard is butylbenzotriazole. As indicated earlier, extensive use of the subject compounds is projected in the water treatment, and in particular the cooling 5 water, industry for the protection of the structural parts of cooling water systems, where such parts are fabricated from copper and/or copper alloys and the water contained in such is aggressive thereto. The compounds of the invention may be'added to the system or 10 applied to the capper surfaces either alone or in conjunction with other treatment agents. If the benzotriazole compounds are used for the treatment of cooling water systems, they may be added individually as an aqueous solution, or may be combined with the well known corrosion ■j 15 inhibiting compositions"-"de signed to protect the ferrous structures of the cooling water system. For example, these compounds may be formulated in the proper amount (sufficient that when the total product is added to the cooling water, there is a sufficient amount of the present compound(s) to perform the function and provide the 20 protection) with such well known treatments. Such treatments include: the Dianodic II treatments which are directed to the use •' of an acrylic acid hydroxyalkylacrylate/orthophosphate to provide corrosion protection. (Note NZ Patent Specification No. 193766 which is incorporated herein in its entirety by reference); the zinc chromate 25 and/or phosphate-based treatments; the phosphonate containing treatments; the poly and orthophosphate-polymer treatments, e.g., those containing polyacrylic acids polymers, sulfonated styrene-maleic anhydride polymers, acrylic acid/acrylamide cop&l-ymers-the I \ 20 JAN 1988$! ^ - o. ' 11 2 -4- acrylamidomethylpropane sulfonate-based polymers [See Betz U.S. Patent 3,898,037 which is incorporated in its entirety herein by reference] and the like. For more definitive explanations, note the BETZ Handbook at the sections cited earlier, the subject matter of which is also incorporated herein by reference. The compounds of the invention would appear to be utilizable with any ferrous metal protective system whether it be by the passivation technique or the barrier protection technique. As earlier indicated, the compounds hfcve the formula The atoms comprising the structure are numbered in order to lend greater specificity to the particular compounds which have been found to be unexpectedly superior, i.e., the 4 or 5 butyl-benzotri azoles. R H While the R group has earlier been described as having to Cg groups, the compounds are more specifically represented as follows: 2 121 -5- and the like, where the 4 or 5 position is preferred. It is also possible to substitute additional function groups both on the hydrocarbon group and in the ring at the 6 and/or 7 positions. Such groups as alkyl, haloalkyl, halo, amino, alkoxyl, and carboxamido groups might be useful. .. ,4.-j „ , ... r . • _- . T ' . - ■■■.••■fx—' - •■iVtWIV'": 21212 6 f -6- The compounds of the invention should be used, obviously. In an amount sufficient for the purpose, but more specifically can be added to the aqueous system In an amount of from about 0.1 to 200 parts per million parts of water in said aqueous system. 4^ 5 Figures 1 through 4 are described in the Results. Specific Examples In order to establish the efficacy of the present compounds over the known compounds, the following experiments and studies were conducted. 10 Description of Experiments I. Electrochemical Methods Since corrosion is a primarily electrochemical phenomenon it is possible to use electrochemical techniques to study its mechanisms and activity. The experiments are performed by 15 placing an electrode (the working electrode) of the metal alloy of interest in a suitable medium (a conductive liquid) along with a suitable reference electrode (results reported herein are referenced to the Saturated Calomel Electrode [SCE]), and by means of various t>_es of electronic devices 20 (generally referred to as potentiostats) controlling either the electrostatic potential (voltage) or current, and simultaneously measuring the resultant current or potential. The first major technique is potentiostatic polarization or "Tafel" polarization. 2 121 -7- Tafel Polarization Since during the corrosion process electrons are transferred from the corroding metal to the environment, the rate of electron flow, or current, is directly related to the rate of corrosion using Faraday's law: N 1 i/nF where N = number of moles undergoing reaction per unit time (i.e., the corrosion rate)' n = number of electrons per atom required (or equivalents per mole) i = electric current (charge per unit time) F = Faraday (coulombs per equivalent) The rate of corrosion, expressed as an average penetration rate, is given by: C. R. = (N x At.Wt)/(d x A) where C. R. = corrosion rate in suitable units N = previously defined At. Wt. = mass per mole of the alloy Z 1212 6 -8- d » density of alloy A « surface area of test specimen The polarization technique involves perturbing the system electrically well away from the corrosion potential so as to 5 effectively suppress one of the current components, thereby allowing a determination of the other component. Thus, by applying a positive potential the cathodic reaction is suppressed, allowing measurement of anodic currents. Applying negative potentials accomplishes the opposite process. By 10 suitable mathematical treatment of the data the corrosion current can be determined. Furthermore, detailed analysis of the current-potential relationships reveals mechanistic details. For example, comparison of the shapes of the anodic and cathodic curves with and without inhibitors can reveal the 15 principal mode of inhibition. In the attached data, showing such tests, it can be seen that the cathodic reduction of oxygen is most significantly affected by the inhibitor molecules, and that butylbenzotriazole exhibits the greatest degree of cathodic reaction retardation. 20 B. Linear Polarization One drawback of Tafel Polarization is that the passage of significant currents through the sample and solution causes permanent changes in the system. Repeated measurements are precluded as the results cannot be 25 related to a known state of the system. Typical changes are solution pH, . lution composition, and surface structure of the test specimen. Linear polarization *> 1 * -9- solves this problem by using very small perturbation currents so that any changes 1n the state of the system remain negligible. The non-11nearlty of system response, however, creates complications with respect to the treatment of the data. Various algorithms are available for such treatment and are employed in computer programs used for this purpose. A measurement of the instantaneous slope of the current-potential curve at the corrosion potential has units of ohms, or electrical resistance Jjnits. For samples of the same composition and surface area this polarization resistance value is inversely proportional to the corrosion rate. Thus, the greater the resistance the lower the corrosion rate. This technique has the advantage of allowing repeated measurements on the same system, but sacrifices the mechanistic details obtainable by Tafel polarization. The attached linear polarization data shows a significant and completely unexpected improvement for butylbenzotriazole over tolyltriazole and benzotriazole. Performance Studies Apart from the purely electrochemical aspects of corrosion and its inhibition there arises the question of the effect of external conditions. Of primary interest to open recirculating cooling system treatment technology are the effects of water chemistry, flowrate, and temperature. 126 -10- Accordingly, test equipment 1s designed to simulate a wide range of potential operating conditions, and additionally, provision 1s made for the Insertion of test specimens. These specimens may then be studied visually, electrochemically or 5 gravimetrlcally as is desired. The two principal tests employed for the current studies are spinners and ^ recirculators (RTU's). A. Spinner Tests N i A 17 liter tank is provided in which the test water is i 10 placed. Provision is made for maintaining constant temperature in the range of room temperature to 212*F (100*C); additionally, air saturation of the test solution is maintained. Cleaned, weighed metal samples in the form of coupons (metal strips of varying dimension based on the 15 alloy) are affixed to the periphery of a mandrel. The coupons are then immersed in the test solution and rotated around a vertical axis at constant speed. The rim i velocity is maintained at 1.6 feet/second. Following exposure for a predetermined period (typically 20 3-7 days) the test coupons are removed and inspected, cleaned, dried and weighed. From these data corrosion rates are calculated. B. Recirculatinq Test Unit fRTU) 25 This test procedure is conceptually similar to the spinner test, but rather than rotate the test specimens in a stationary liquid the test specimens are stationary and 2 12 126 -lithe liquid is circulated at a fixed but adjustable velocity. Additionally, means are provided to replenish the test solution at a fixed, adjustable rate and to regulate pH to within + 0.2 pH units. Provision is made for conducting electrochemical corrosion measurements in the flowing stream. Furthermore, a test specimen can be inserted into the flowing stream to which a constant heat flux may be applied via an internal resistance heating device in order to regulate the surface temperature of the specimen. Results of Tests A. Tafel Polarizations Copper electrodes were placed in the test vessel containing 0.1N sodium sulfate adjusted to pH 7.0 and are air saturated. A control had no treatment, and subsequent tests incorporated one part-per-mil1 ion (ppm) of either benzotriazole (BZT4, tolyltriazole (TTA), or butylbenzotriazole (b-BZT). A potential sweep of 10 millivolts per minute (mY/min) from -550 mV to + 250 mV (versus a saturated calomel reference electrode) was applied. A plot of log current vs. potential is shown in Figure 1. The salient feature is the decrease in cathodic current at a given potential as one examines the series: no treatment (1); tolyltriazole (2); b-BZT (3 and 4). Abatement of the anodic current is the same for TTA and b-BZT, and is several orders of magnitude below that of the untreated control. ,4-^. **-!•« w3«.V»»Jh.«»W.-*^ 2 1 2 t 2 fS5 -12- These results show that both TTA and b-8ZT act as anodic and cathodic Inhibitors, that the degree of anodic inhibition Is essentially the same for both, and that b-BZT is a superior cathodic inhibitor to TTA by a factor 5 of 10-100 fold. Figure 2 is a cathodic-only sweep which further illustrates the increase in cathodic inhibition of b-BZT over that of TTA. The decrease in cathodic current at equal potential is tenfold for b-BZT versus TTA. >~ 10 B. Li near Polarization/Recirculator 1. Prefilmed Tests Cleaned electrodes were exposed to 10 ppm (pH * 7) solutions of TTA, b-8ZT, and BZT for 24 hours. The electrodes were placed in holders in the test rack of 15 an RTU. The test conditions were Ca (as CaCO^) 600 ppm, Mg (as CaCO^) 300 ppm, Cl~ 1000 ppm, pH = 7, 120*F. Linear Polarization vs. time is as follows: Z 1212 -13- Elapsed Time Polarization Resistance (hrs) (ohms) Control TTA BZT b-BZT 3 186 223 360 3030 ■ 5 4 308 348 468 9804 22 533 520 195 6667 26.5 526 556 342 743 28 563 602 377 1099 —- 46 442 526 402 381 10 The data show that the new material (rightmost column) is 10 to 30 times as inhibitive as TTA or BZT. Fluctuations in the data are due to slight oscillations of the pH over time. In another test using the same water conditions but 15 prefilming at 100 ppm the results are as follows: Polarization Resistance (ohms) Elapsed Time (hrs) Control TTA b-BZT 2 580 13,000 601,500 20 22.5 2,900 60,100 455,000 28.5 8,250 91,950 305,350 50.0 14,200 178,600 434,800 122.5 16,000 69,600 298,500 189.5 21,300 55,600 232,600 25 215.5 16,400 42,100 219,200 315.5 10,000 27,400 110,400 (f^ 26 -14- The results indicate an inhibitive effect for the new material on the average of five times that of TTA. Of greater significance Is the failure of the TTA film after 190 hours whereas the film formed by b-BZT was still more inhibitive than the average TTA film for an additional 150 hours at least as seen in Figure 3. In another run the water conditions were as follows: 500 ppm Ca (as CaCO^), 300 ppm Mg (as CaCO-j), 440 ppm CI". The test electrodes were prefilmed at 100 10 ppm. Results were as follows: Elapsed Time Polarization Resistance (hrs) (ohms) Control TTA BZT b-BZT 2 816 9,592 12,346 131 ,148 15 21 20,513 20,725 72,727 210,526 48 21,740 19,048 48,780 248,440 117 15,504 15,873 16,529 110,497 171 15,000 11,696 23,256 231,231 214 14,286 8,811 8,811 57,971 20 264 7,512 7,326 6,400 16,260 Figure 4 is a plot of resistance vs. time. Again the results indicate a significant increase in the inhibitory power and film longevity for b-BZT. *M2.'S.r---tl>l.\rv.:wH!ivr"rsrt»»Vj;;-> .-+.-: ■■<•■ ■ :■■, .-.. >—-1 -fftp™ 126 -15- 2. On-Hne Filming Test Another test, designed to mimic real field conditions, was run using the following water conditions: Ca 780 ppm (as CaCO^), Mg 280 ppm (as CaCO^), CI" 12 5 ppm, S0^ 3 1000 ppm, pH * 7.3, 120*F. This time prefilming was at 10 ppm, but the filming was done under dynamic conditions in the flowing system for four hours rather than in a static jar for 24 hours as was done in the previous tests. This is a realistic 10 test of an actual field use since the on-line pretreatment is the only mode possible in a real system. Elapsed Time Polarization Resistance (hrs) (ohms) 15 Control b-BZT b-BZTa 2 1,231 366,972 48,103 24 19,753 185,803 183,908 45 56,338 119,403 164,948 117 75,472 120,301 20 283 61,766 105,960 95,808 a prefilmed statically at 100 ppm k blown fuse precluded measurement 3. Spinner Tests The b-BZT was tested against TTA at three *•- — - .. ■ ..y :->-*■ "':•■■■ 2 12 1 -16- concentration levels. The water was as follows: Ca (as CaCO-j) 170 ppm, Mg (as CaCO^) 110 ppm, 15 ppm SfOj, pH = 7.0, 120"F. The corrosion rates of Admiralty brass were as follows: <"**■ 5 Treatment Corrosion Rates (mpy) _0 0.5 ppm 1.0 ppm 2.0 ppm Control 1.6 TTA - 0.65 0.59 0.42 b-BZT - 0.42 0.44 0.48 J 10 These tests, which are not particularly stressful or precise, show that b-BZT is equal to or superior to TTA. While this invention has been described with respect to particular embodiments thereof, it is apparent that t 15 numerous other forms and modifications of this invention will be obvious to those skilled in the art. The appended claims and this invention generally should be construed to cover all such obvious forms and modifications which are within the true spirit and 20 scope of the present invention. </div>

Claims

<div class="application article clearfix printTableText" id="claims"> 2121 WHAT t/WE CLAIM IS: "17"

1. A method of inhibiting the corrosion of non-ferrous metals in - contact with an aqueous system, which comprises adding to said system a sufficient amount for the purpose of a water soluble compound having the formula: tfJJJLfceP wherein R isan^iydrocarbon group containing from 3 to 8 ■ -iio carbon atoms. trfo

2. A method according to claim 1 wherein R contains from 4 to 6 carbon atoms. 15

3. A method according to claim 2 wherein said compound is added to said aqueous system in an amount of 0.1 to 200 parts per million parts of water in said system.

4. A method according to claim 3 wherein the non-ferrous metal is or contains copper. 20

5. A method according to claim 4 wherein the aqueous system is a cooling water system.

6. A method according to claim 5 wherein the water contained within the cooling water system and/or the conditions of 20 JAN 1988 m! .iwi'i'B/'tK 1 212126 -18- t' •*; operation of said system is or are such as to provide a highly corrosive medium for said copper or copper containing metal.;f •5;7._- A method according to claim 1 wherein R is an alkyl of from 3 to 8 carbon atoms.;\;■I 5 8.

A method according to claim 7 wherein the non-ferrous metal is;1;^ or contains copper.;O;9.

A method according to claim 8 wherein the aqueous system is a (.;cooling water system. ' !;I 10.

A method according to claim 9 wherein said compound is added;1 10 to the aqueous system in an amount of 0.1 to 100 parts per million parts of water in said system.;2;11.

A method according to claim 9 wherein the water contained J " within the cooling water system and/or the conditions of;\ operation of said system is or are such as to provide a highly;15 corrosive medium for said copper or copper containing metal.;12.

A method according to claim 1 wherein the compound is a butylbenzotriazole.;13.

A method according to claim 12 wherein said compound is added to said aqueous system in an amount of 0.1 to 100 parts per 20 million parts of water in said system.;14.

A method according to claim 13 wherein the non-ferrous metal is or contains copper.;e;^ 0\s;/ 'A;.

V A\;2 20 JAN 1988 mj;,;.

V_ ««•/;V; c fr i ';21212;-19-;15.

A^method according to claim 14 wherein the water contained within the cooling water system and/or the conditions of operation of said system is or are such as to provide a highly corrosive medium for said copper or copper containing metal.;5 16.

A method according to claim 15 wherein said system is a cooling water system.;17.

A method according to claim 16 wherein said compound is 4 or 5 butylbenzotriazole.;18.

An improved method of inhibiting the corrosion of metal parts in contact 10 with an aqueous system, said metal parts being composed of both ferrous and non-ferrous metals, which comprises adding to said aqueous system a sufficient amount for the purpose of a corrosion inhibitor composition for said ferrous metal, the improvement being also adding to said aqueous system an effective amount for the purpose of a corrosion inhibitor for said non-ferrous metal, said corrosion inhibitor comprising a compound represented by the formula:;R;20;group containing from 3 to 8;1;

20 JAN 1988m,;212126;-20-;19. A^method according to claim 18 wherein said hydrocarbon group contains from 4 to 6 carbon atoms.;* C; 20.- A method according to claim 19 wherein the water contained within the cooling water system and/or the conditions of 5 operation of said system is or are such as to provide a highly corrosive medium for copper or copper containing metal.

21. A method according to claim 20 wherein the aqueous system is a cooling water system.

22. A method according to claim 21 wherein the non-ferrous metal 10 is or contains copper.

23. A method according to claim 20, 21 or 22, wherein the compound is butylbenzotriazole.

24. A composition~effective for inhibiting the corrosion of metallic parts or systems composed of both ferrous and 15 non-ferrous metals in contact with water, which composition comprises a corrosion inhibiting composition for said ferrous metals, and a corrosion inhibitor for said non-ferrous metals, comprising a compound of the formula "20 212126 -21- wherein R isanl hydrocarbon group containing 3 to 8 carbon atoms. 1 i

25. _ A composition according to claim 24 wherein said group contains from 4 to 6 carbon atoms. '

26. A composition according to claim 25 wherein the group is a butyl.

27. A composition according to claim 26 wherein said corrosion inhibitor for said non-ferrous metal "is 4 or 5 butylbenzotriazole.

28. A composition according to claim 27 wherein said non-ferrous metal is or contains copper.

29. A method as claimed in any one of claims 1 to 23 when performed substantially as hereinbefore described with reference to any example thereof.^

30. A composition as claimed in any one of claims 24 to 28 when performed substantially as hereinbefore described with reference to any example thereof. DATED THIS io DAY OF ORNufliZ-H f?$5 A. J. PARK & SON per 1eJki AGFMTS FOR THF APPLICANTS- </div>