JP2768538B2 - New corrosion inhibitors for copper and copper alloys. - Google Patents

Abstract

The use of alkoxybenzotriazoles to inhibit the corrosion of metallic surfaces in contact with an aqueous system. Systems and compositions containing alkoxybenzotriazole are also claimed.

Description

DETAILED DESCRIPTION OF THE INVENTION Benzotriazole, mercaptobenzothiazole and tolyltriazole are known as copper corrosion inhibitors. See, for example, U.S. Patent No. 4,675,158 and the references cited therein. Also, U.S. Pat. No. 4,744,950, which discloses the use of alkoxybenzotriazoles as corrosion inhibitors, and U.S. Pat. No. 4,744,950 which discloses the use of benzotriazole / tolyltriazole mixtures in water treatment compositions for multi-metallic corrosion control No. 4,406,811
See issue No. It is known that 5-methoxybenzotriazole (anisotriazole) is used in a corrosion inhibiting composition [Japanese Patent Laid-Open No. 59-222,589 (December 1984)].
14); Chemical Abstracts, 102: 153153b], the use of alkoxybenzotriazoles in the field of water treatment is not known.

The present invention relates to the use of alkoxybenzotriazoles as corrosion inhibitors, especially for copper and copper alloys. These compounds form long lasting protective films on metal surfaces in contact with aqueous systems, especially on copper and copper alloy surfaces.

The present invention is a method for inhibiting corrosion of a metal surface in an aqueous system, comprising the following formula: Wherein RO is located at the 4-, 5-, 6- or 7-position, and R is a substituted or unsubstituted straight or branched C ₃
~ _C18 alkyl. A) adding to the aqueous system an effective amount of a compound selected from the group of compounds having In particular, the present invention relates to a method for inhibiting corrosion of copper and copper alloy surfaces.

The present invention also provides (a) aqueous water, and (b) the following formula: (Wherein, RO is located at position 4, 5, 6, or 7;
And R are substituted or unsubstituted straight-chain or branched
C ₃ -C ₁₈ alkyl. The present invention relates to a composition for inhibiting metal surface corrosion, comprising a compound selected from the group of compounds having: The water in the composition of the present invention may be cooling water.

The present inventors have found that alkoxybenzotriazole is an effective corrosion inhibitor. These compounds
It forms a durable, long-lasting film on metal surfaces, including but not limited to copper and copper alloy surfaces. Alkoxybenzotriazoles are particularly effective inhibitors of copper and copper alloy corrosion,
In particular, it can be used to protect multimetal systems containing one or more copper or copper alloys and other metals.

We also note that alkoxybenzotriazoles can deactivate soluble copper ions, thereby preventing galvanic dissolution of iron or aluminum in the presence of copper ions, thereby concomitant with galvanic deposition of copper. Was found. This minimizes corrosion of aluminum and iron. These compounds also indirectly suppress the galvanic reaction by preventing the formation of soluble copper ions due to corrosion of copper and copper alloys.

Isomers of the aforementioned 5-alkoxybenzotriazoles can also be used. The isomers at the 5- and 6-positions are mutually interchangeable by simply transferring the prototropy of the hydrogen at the 1-position to the 3-position and are considered functionally equivalent. The isomers at the 4- and 7-positions are difficult and expensive to produce, but are thought to have functions equivalent to or better than the isomers at the 5- or 6-position. As used herein, the term "alkoxybenzotriazole" is intended to mean 5-alkoxybenzotriazole and its 4-, 6-, and 7-isomer.

Substituted alkoxybenzotriazoles and their isomers can also be used. Therefore, in the structural formula (I), when R is an unsubstituted alkoxy group having 3 to 18 carbon atoms, one or more of the CH ₂ groups of R can be substituted with oxygen or NH. Specific examples include, but are not limited to, oxapentyl group _{(CH 3 CH 2 OCH 2 CH} 2 -), Azapenchiru group (CH ₃ CH ₂ N
HCH ₂ CH ₂ —) and a 6-oxa-3-aza-octyl group (CH ₃ CH ₂ OCH ₂ CH ₂ NHCH ₂ CH ₂ —). The term "substituted alkoxybenzotriazole" as used herein includes compounds wherein R in structural formula (I) is an oxaalkoxy group and / or an azaalkoxy group.
Substituted alkoxybenzotriazoles also include a halogenomethylene group, CHyHz, where y is 1
Or zero, z is 1 or 2, X is a Group 7 element, and X is either the same or different halogen atoms). Also one or more of the methylene groups may be replaced by oxygen or sulfur,
The result is, for example, an alcohol, thioalcohol, keto or thioketo group. The carbon of the ether bond must not be substituted. One or more methylene groups are not substituted, resulting in ethylene units or acetylene units. Substituted alkoxybenzotriazoles also
R in structural formula (I) includes compounds containing an aromatic. Specific examples include, but are not limited to, those in which R is (In the formula, n 1 to 9, X is hydrogen, halogen, nitro, carboxy, cyano, amido, substituted amino or C ₁ -C ₃ alkoxy.) And Wherein n is 1-8 and X is as defined above.

The alkoxybenzotriazoles of the present invention require the use of an effective amount. As used herein, the term "effective amount" refers to an amount of an alkoxybenzotriazole effective to inhibit the corrosion of a given aqueous system.

More particularly, the alkoxybenzotriazoles, substituted alkoxybenzotriazoles and their isomers of the invention have at least 0.1 ppm, preferably at least 0.1 ppm, based on aqueous systems in contact with metal surfaces, especially copper and copper alloy surfaces.
When added at a concentration of 0.5 to 100 ppm, most preferably 1 to 10 ppm, corrosion of metal surfaces, particularly copper and copper alloy surfaces, is effectively suppressed. The highest concentration is determined by economic considerations at the particular point of use, while the lowest concentration is determined by operating conditions such as pH, dissolved solids and temperature.

The alkoxybenzotriazoles of the present invention can be prepared by known methods. For example, the alkoxybenzotriazoles of the present invention are prepared by contacting 4-alkoxy-1,2-diaminobenzene with an aqueous solution of sodium nitrite in the presence of an acid such as sulfur, and then separating the resulting oily product from the aqueous solution. Can be prepared. 4-
Alkoxy-1,2-diaminobenzene can be obtained from any number of sources.

The compounds of the present invention can be used as water treatment additives in industrial cooling water systems, gas scrubber systems or any water system that comes into contact with metal surfaces, especially surfaces containing copper and / or copper alloys. These compounds can be administered alone or as part of a treatment formulation, including, but not limited to, biocides, scale inhibitors, dispersants, defoamers and other corrosion inhibitors. The alkoxybenzotriazole and substituted alkoxybenzotriazole of the present invention can be administered intermittently or continuously.

Copper or Admiralty brass or 90/10 copper
Certain copper corrosion inhibitors must be used for the treatment of cooling water in contact with the surface of a copper alloy such as nickel. These corrosion inhibitors include: 1. Minimize corrosion of copper or copper alloy surfaces, including general corrosion, de-component corrosion and galvanic corrosion; 2. Galvanic "plating out" of soluble copper ions on iron or aluminum. ) "To minimize problems.

That is, soluble copper ions will enhance the corrosion of iron and / or aluminum components that come into contact with the aqueous system. This means that the copper ions are reduced by the iron or aluminum metal and the iron or aluminum metal is thereby oxidized, resulting in "precipitation" of the copper metal on the iron surface. This chemical reaction not only destroys the protective film of iron or aluminum, but also results in localized galvanic cells, resulting in pitting of the iron or aluminum.

Tolyltriazole, benzotriazole and 2-
Conventional copper inhibitors such as mercaptobenzothiazole are commonly used as copper inhibitors in aqueous systems. These inhibitors are generally administered continuously because the durability of the protective film is limited.

Thus, when applying conventional inhibitors to once-through systems or systems with high blowdown rates, it is generally uneconomical to administer the inhibitors continuously. In addition, conventional inhibitors have little expected protection against chlorine-induced corrosion.

It is known that continuous administration of 5-alkoxybenzotriazoles is not required to inhibit copper corrosion (see U.S. Pat. No. 4,744,950), but the production of such alkoxybenzotriazoles is relatively low. And is therefore only applicable to a limited number of areas for economic reasons. Other disadvantages include the relatively slow passivation of copper alloys in certain types of water, poor copper passivation in waters with high dissolved solids, and chemical resistance to chlorine. Is low.

An object of the present invention is to provide an inhibitor which forms a durable protective film and overcomes the above-mentioned limitations.

These objects can be achieved by using alkoxybenzotriazoles, substituted alkoxybenzotriazoles and isomers of these compounds to minimize corrosion and / or to provide durability on metal surfaces, especially copper and copper alloy surfaces. This gives a hydrophobic protective film having a certain characteristic.

The alkoxybenzotriazole according to the invention can be administered intermittently in a cooling water system. Depending on the aggressiveness of the water, the time between administrations can range from days to months. Thus, the average inhibitor requirement is low, which is advantageous with respect to water treatment and environmental impact.

Preferred as alkoxybenzotriazoles are those in the range from propyloxybenzotriazole to nonyloxybenzotriazole.
Most preferred compounds are butyloxybenzotriazole, pentoxybenzotriazole and hexyloxybenzotriazole.

EXAMPLES The following examples serve to illustrate the effectiveness of the compounds according to the invention as corrosion inhibitors for copper and copper alloys. However, these examples do not limit the scope of the invention in any way.

Examples 1-4 Durability of Protective Film In these examples, copper specimens were prepared at pH 7.5 and at a temperature of 50.
It was pretreated by immersion in aerated water at ℃. This water contained a specific concentration of an inhibitor that formed a protective film on the test piece.

After 24 hours, they were transferred to highly corrosive water without inhibitor to determine the persistence of the overcoat. The corrosion rate was measured using linear polarization and the passivation was measured.

The properties of the pretreatment water and the erodible water are listed in Tables 1 and 2, respectively.

Table 3 shows the corrosion results. The results are reported as "post-passivation corrosion rate" for the passivation step and "corrosion rate in aggressive water without inhibitors".

The maximum duration of the test was 15 days, at which point the test was terminated.

As shown in Table 3, 5-pentyloxybenzotriazole provides 99% inhibition, even after 15 days of exposure to aggressive water, whereas the durability of the protective layer of ethyloxybenzotriazole is Within 2 days or less, the conventional inhibitor tolyltriazole had no effect within 1 day.

Examples 5-8 Chlorine Resistance These examples, performed in a dynamic test apparatus, demonstrate the protective coating formed by alkoxybenzotriazole against the corrosiveness of chlorine to heat transfer brass tubes and copper immersed plate specimens. It indicates resistance.

The dynamic test equipment used in these examples consisted of eight water baths, a heater-circulator and a coil heater to provide the required heat flux. The coil heater was designed so that it could be fixed tightly around the 0.95 cm (3/8 ") OD tube used in the test. The flow in the tube was measured using an inline rotameter with a dose of 400 ml / min. The input to the heater was controlled by a rheostat so that the temperature difference across the tube could be varied.The temperature at the inlet and outlet of the tube was accurate to 0.056.
Monitoring was performed with a thermocouple attached to a 0.1 ° F. (° C.) digit reader. The device was completely sealed to minimize evaporation. The linear velocity in the heating tubes in the 0.66 m / sec (2.2fps), N _RE
Is about 9,350. The heat flux is 22,400 to 28,000 Kcal / hr · m ² (8,000 to 10,000
Btu / hr · ft ² ) was selected.

The corrosion rate of the heating tube was measured by a weight loss method described in "Production, cleaning and standard evaluation method of corrosion test piece" of ASTM Standard G1-81. The corrosion rate of the immersion test specimen was measured using the Petrolite Model M1010 Corrosion Data Acquisition System (Petrolite Model M
1010 Corrosion Data Acquisition System). This method measures the corrosion rate at a particular time and is therefore useful for tracking the direct effect of chlorine concentration on corrosion rate.

 The test piece was tested according to the following procedure.

1. The cleaned test specimen was placed in the above test apparatus and the specified amount of inhibitor was added.

The specimens were then passivated for 24 hours, where they were placed in inhibitor-free water.

2. Chlorine was added so that the initial concentration of free chlorine was 1 mg /. The corrosion rate of each specimen was monitored for one hour.
During this time, the chlorine concentration usually decreased from 1 mg / to about 0.7 mg /.

3. After 1 hour, each specimen was placed in fresh water without inhibitor and chlorine. Next, the decrease in the corrosion rate of each test piece, ie, the recovery corrosion rate, was measured.

4. Steps 2 and 3 were repeated in a 24-hour cycle for a total of 4 cycles, with one additional cycle after the weekend.

5. After 7 days, the weight loss of the heating tube was measured.

 Table 4 shows the composition of the water used in this test.

The test results are shown in Table 5. The rate of corrosion of the heat transfer admiralty brass tube indicates the cumulative corrosion that has occurred during the 7 day test period. As can be seen from the table, pentyloxybenzotriazole shows 90% corrosion protection and hexyloxybenzotriazole shows 85% corrosion protection.

In contrast, the corrosion protection of tolyltriazole, which is widely used as an inhibitor, is only 36%. Also, immersed copper probes treated with either pentyloxybenzotriazole or hexyloxyl benzotriazole had no significant effect when exposed to chlorine for one hour with chlorine, while treatment with tolyltriazole Copper probe or control probe
In the presence of chlorine it showed a significantly higher corrosion rate.

Examples 9-10 Dynamic Testing Cooling Tower Test These examples demonstrate that pentyloxybenzotriazole has excellent chlorine resistance and sustained membrane protection in a dynamic system simulating the operating variables typically found in industrial cooling towers. It is for explaining that it has the property. Simulated operating factors include blowdown, heat transfer surfaces, dynamic flow, evaporative cooling, concentration cycles and conventional chlorination methods.

The test cooling tower used contained two single tube heat exchangers. The cooling water was flowed in series on the outer wall side (annular space) of the heat exchanger, and the hot water was circulated in the pipe in counterflow in series. In addition to the main recirculation circuit passing through the cooling tower, this device is equipped with N to maintain the cooling water linear velocity in the heat exchanger.
Included a recirculation loop from the o.2 heat exchanger outlet to the No. 1 heat exchanger inlet. The outer wall of the heat exchanger is constructed of Plexiglass, so that the surface of the heat exchanger can be observed during the test. For such a test, a 90/10 copper-nickel tube was placed in a No. 2 heat exchanger.

Devices for monitoring and controlling test variables include pH and conductivity indicators, / controllers, PAIR corrosion rate indicators, temperature indicators / controllers, and air and water flow rotometers. Was.

A PAIR probe was installed after the outlet of the No. 2 heat exchanger to continuously monitor the 90/10 copper-nickel corrosion rate. Plates for 90/10 copper-nickel corrosion testing were mounted in a recirculation loop. The PAIR tank and the corrosion test loop were assembled with plexiglass so that the Corrater electrode and the corroded plate specimen could be observed.

Tubes, corroded plate specimens and PAIR used for these tests
The cleaning procedure used to make the electrodes is ASTM G1
-81.

In preparation for these tests, stainless steel tubing was provided in a heat exchanger and the apparatus was filled with composition water. It took 3 days for the water to recirculate and concentrate to the target concentration cycle. The target water composition is Example 5.
8 was the same composition. After reaching the target cycle, the stainless steel tubing was removed and the specimen was attached (tube, plate specimen and PAIR electrode). At this point, blowdown began and the desired copper inhibitor was added. The inhibitor gradually replaced the cooling water and became depleted.
That is, after 3 days, the concentration of the inhibitor was 1/8 or less of the original inhibitor concentration, and after 5 days, almost no control agent remained.

Table 6 shows the corrosion rate immediately before chlorine was attached to the apparatus and the maximum corrosion rate when chlorine was present. The amount of chlorine added was such that the free chlorine residue was 0.2 mg / -0.5 mg /. This chlorine concentration then disappeared by blowdown, evaporation and reaction.

As is evident from Table 6, pentoxybenzotriazole effectively passivated 90/10 copper-nickel specimens, and surprisingly, even when the inhibitor was completely depleted. Significantly reduced the aggressiveness of chlorine.

Examples 11-12 Protective film persistence The same procedure was used as in Examples 9-10, except that no chlorine was added to the system. The purpose of this test was to determine the persistence of the protective film formed by the inhibitor after it was drained from the system by replacing the original water.

The results are shown in Table 7, where pentoxybenzotriazole remained protective over the two week test period. This is particularly surprising, given that by day 5 the original concentration of the inhibitor had almost completely disappeared. The trial was terminated after two weeks, due to mere implementation constraints of time and expense.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-56288 (JP, A) JP-A-59-222589 (JP, A) JP-A-52-93771 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) C23F 11/00, 11/14 C02F 5/10 C07D 249/18

Claims (7)

(57) [Claims] 1. A method for inhibiting metal surface corrosion in an aqueous system, comprising the following formula: Wherein RO is located at the 4-, 5-, 6- or 7-position, and R is a substituted or unsubstituted straight or branched C ₃
~ _C18 alkyl. A) adding to the aqueous system an effective amount of a compound selected from the group of compounds having 2. The aqueous system is charged with the compound in an amount of 0.1 to 10.0 m.
The method according to claim 1, wherein g / liter is added. 3. The method of claim 1 wherein said compound is selected from the group consisting of butyloxybenzotriazole, pentyloxybenzotriazole and hexyloxybenzotriazole. 4. The method of claim 2, wherein said compound is selected from the group consisting of butyloxybenzotriazole, pentoxybenzotriazole and hexyloxybenzotriazole. 5. The method of claim 1, wherein said metal surface is a copper or copper alloy surface. 6. The method of claim 2, wherein said metal surface is a copper or copper alloy surface. 7. An aqueous system of water, and (b) the following formula: Wherein RO is located at the 4-, 5-, 6- or 7-position, and R is a substituted or unsubstituted straight or branched C ₃
~ _C18 alkyl. A composition for inhibiting metal surface corrosion, comprising a compound selected from the group of compounds having: