Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
  • C23F11/00—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent
  • C23F11/08—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent in other liquids
  • C23F11/10—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent in other liquids using organic inhibitors
  • C23F11/14—Nitrogen-containing compounds
  • C23F11/149—Heterocyclic compounds containing nitrogen as hetero atom

Definitions

• Benzotriazole, mercaptobenzothiazole and tolyltriazole are well known copper corrosion inhibitors.
• U.S. patent 4,675,158 and the references cited therein see U.S. patent 4,744,950, which discloses the use of lower alkylbenzotriazoles as corrosion inhibitors and U.S. patent 4,406,811, which discloses the use of benzotriazole/tolyltriazole blends in water treatment compositions for multimetal corrosion inhibition.
• the instant invention relates to the use of higher alkylbenzotriazoles as corrosion inhibitors, particularly copper and copper alloy corrosion inhibitors. These compounds from long-lasting protective films on metallic surfaces, particularly copper and copper alloy surfaces, in contact with aqueous systems.
• the instant invention is directed to a method of inhibiting the corrosion of metallic surfaces, particularly copper and copper alloy surfaces, in contact with an aqueous system, comprising adding to the aqueous system being treated an effective amount of a higher alkylbenzotriazole compound having the following structure: wherein n is greater than 6 and less than or equal to 12; and isomers of such compounds.
• a higher alkylbenzotriazole compound having the following structure: wherein n is greater than 6 and less than or equal to 12; and isomers of such compounds.
• Branched-chain C6-C12 alkyls can also be used, though straight chain compounds are preferred as they are believed to provide more persistent films in the presence of chlorine.
• the instant invention is also directed to an aqueous system which is in contact with a metallic surface, particularly a copper or copper alloy surface, and which contains a higher alkylbenzotriazole.
• compositions comprising water, particularly cooling water, and a higher alkylbenzotriazole are also claimed.
• higher alkylbenzotriazoles are effective corrosion inhibitors. These compounds form durable, long-lasting films on metallic surfaces, including but not limited to copper and copper alloy surfaces. Higher alkylbenzotriazoles are especially effective inhibitors of copper and copper alloy corrosion, and can be used to protect multimetal systems, especially those containing copper or a copper alloy and one or more other metals.
• the instant inventors have also found that the instant alkylbenzotriazoles de-activate soluble copper ions, which prevent the galvanic deposition of copper which concomminantly occurs with the galvanic dissolution of iron or aluminum in the presence of copper ions. This minimizes aluminum and iron corrosion. These compounds also indirectly limit the above galvanic reaction by preventing the formation of soluble copper ions due to the corrosion of copper and copper alloys.
• Isomers of the above described higher alkylbenzotriazoles can also be used.
• the 5 and 6 isomers are interchangeable by a simple prototropic shift of the 1 position hydrogen to the 3 position and are believed to be functionally equivalent.
• the 4 and 7 isomers are believed to function as well as or better than the 5 or 6 isomers, though they are more difficult and expensive to manufacture.
• the term "higher alkylbenzotriazoles” is intended to mean 5-alkyl benzotriazoles and 4, 6 and 7 position isomers thereof, wherein the alkyl chain length is greater than 6 but less than or equal to 12 carbons, branched or straight, preferably straight.
• an effective amount of an instant higher alkylbenzotriazole should be used.
• the term "effective amount” refers to that amount of a higher alkylbenzotriazole which effectively inhibits corrosion in a given aqueous system.
• the higher alkylbenzotriazoles inhibit the corrosion of metallic surfaces, especially copper and copper alloy surfaces, when added to an aqueous system in contact with such surfaces at a concentration of at least about 0.1 ppm, preferably about 0.5 to 100 ppm and most preferably about 1-10 ppm. Maximum concentrations are determined by the economic considerations of the particular application, while minimum concentrations are determined by operating conditions such as pH, dissolved solids and temperature.
• the instant higher alkylbenzotriazoles may be prepared by any known method.
• the instant alkylbenzotriazoles may be prepared by contacting a 4-alkyl-1, 2-diaminobenzene with an aqueous solution of sodium nitrite in the presence of an acid, e.g., sulfuric acid, and then separating the resultant oily product from the aqueous solution.
• the 4-alkyl-1,2-diaminobenzene may be obtained from any number of sources.
• the instant compounds can be used as water treatment additives for industrial cooling water systems, gas scrubber systems or any water system which is in contact with a metallic surface, particularly surfaces containing copper and/or copper alloys. They can be fed alone or as part of a treatment package which includes, but is not limited to, biocides, scale inhibitors, dispersants, defoamers and other corrosion inhibitors.
• a treatment package which includes, but is not limited to, biocides, scale inhibitors, dispersants, defoamers and other corrosion inhibitors.
• the instant higher alkylbenzotriazoles can be fed intermittantly or continuously.
• An object of the instant invention is to provide inhibitors which produce more chlorine resistance protective films.
• This object is achieved through the use of higher alkylbenzotriazoles, to provide protective, durable hydrophobic films on metallic surfaces, especially copper and copper alloy surfaces.
• the instant alkylbenzotriazoles allow use of an intermittent feed to cooling water systems. Depending on water aggressiveness, the time between feedings may range from several days to months. This results in an average lower inhibitor requirement and provides advantages relative to waste treatment and environmental impact.
• the preferred alkylbenzotriazoles are within the range of C6-C10 alkylbenzotriazoles.
• the most preferred compounds are heptylbenzotriazole and octylbenzotriazole.
• Table III shows that heptylbenzotriazole and oxtyloxybenzotriazole provided 99% inhibition, even after 15 days exposure to aggressive water, and that tolyltriazole, a conventional inhibitor, failed within one day. This is surprising in view of the teachings of U.S. Patent No. 4,744,950.
• the specimens were transferred to inhibitor-free water of the same composition as the pretreatment water. Chlorine was added so that a initial free residual of 1 mg/L chlorine was obtained. Corrosion rates were measured using linear polarization over the course of one hour. The probes were then transferred to fresh inhibitor-free, chlorine-free water and the corrosion rate was monitored to determine the recovery corrosion rate.
• This chlorination procedure was repeated 8 times on a daily basis, plus an additional time after the weekend period.
• the dynamic test unit for these examples consisted of an 8L reservoir, a heater-circulator and a coil heater to provide the desired heat flux.
• the coil heater was designed to fit securely around the 3/8 ⁇ OD tubes used in the tests.
• Flow through the tube was monitored by an in-line rotameter having a flow capacity of 400 ml/min.
• the power input to the heater was controlled by a rheostat, which made it possible to vary temperature differences across the tubes.
• the tube inlet and outlet temperatures were monitored by thermocouples attached to a digital readout having an accuracy of 0.1 o F.
• the system was entirely enclosed to minimize evaporation.
• the linear velocity through the heated tubes was 2.2 fps, which gave a N Re of approximately 9350. Heat fluxes of 8,000-10,000 Btu/hr-ft2 were chosen as being representative of industrial practices.
• the corrosion rates of the heated tubes were determined by the weight loss method described in "Standard Practice for Preparing, Cleaning and Evaluating Corrosion Test Specimens"; ASTM designation Gl-81.
• the corrosion rates of immersed specimens were determined by linear-polarization using a Petrolite Model M1010 Corrosion Data Acquisition System. This method measures the corrosion rate at a particular time, and is thus useful for following the immediate effects of chlorine concentration on corrosion rates.
• tolyltriazole which is a widely used inhibitor, gave only 36 percent corrosion protection. Also, the immersed copper probes treated with heptylbenzotriazole was not significantly affected by exposure to chlorine over the 1 hour contact time while the copper probes treated with tolyltriazole and the untreated probes experienced dramatically higher corrosion rates in the presence of chlorine.
• the pilot cooling tower system used contained two single tube heat exchangers. Cooling water flowed in series through the shell side (annular space) of the heat exchangers and hot water was circulated through the tubes in series, counterflow. In addition to the main recirculation circuit through the cooling tower, the system also contained a recycle loop from the outlet of the No. 2 Heat Exchanger to the inlet of the No. 1 Heat Exchanger for the purpose of maintaining cooling water linear velocity in the heat exchangers.
• the heat exchanger shells were fabricated of Plexiglass to permit observation of the heat exchanger surfaces during the test run. For these tests, a 90/10 copper/nickel tube was placed in the No. 2 Heat Exchanger.
• Instrumentation for monitoring and control of test variables included a pH and conductivity indicator/­controller, PAIR corrosion rate indicators, a temperature indicator/controller, and rotometers for air and water flows.
• PAIR probes for continuous monitoring of 90/10 copper/nickel corrosion rates were installed after the outlet of the No. 2 Heat Exchanger.
• a corrosion test coupon of 90/10 copper/nickel was installed in the recycle loop.
• the PAIR cells and the corrosion test loop were fabricated of Plexiglass to permit observation of the Corrater electrodes and the corrosion coupons.
• Table IX The results are shown in Table IX.
• the inhibitor was allowed to deplete by gradually replacing the cooling water. Thus, after three (3) days, less than one-eighth of the original inhibitor concentration was present, and after five (5) days, practically no inhibitor remained.
• Table IX shows the corrosion rate just prior to the addition of chlorine to the system and the maximum corrosion rate recorded while chlorine was present. Chlorine was added so that between 0.2 mg/L to 0.5 mg/L free residual of chlorine was present. The chlorine concentration was then allowed to dissipate through blow-down, evaporation, and reaction.
• heptylbenzotriazole effectively passivated the 90/10 copper/nickel specimens and dramatically reduced the aggressiveness of chlorine even, surprisingly, when all of the inhibitor had depleted.
• butylbenzotriazole afforded only minimal protection against attack by chlorine, as seen by both the deteriorating recovery corrosion rate and the large corrosion rate experienced during the chlorination.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Preventing Corrosion Or Incrustation Of Metals (AREA)

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Citations (6)

• 1990
  • 1990-04-30 NZ NZ233492A patent/NZ233492A/en unknown
  • 1990-05-07 AU AU54762/90A patent/AU5476290A/en not_active Abandoned
  • 1990-05-07 CA CA002016150A patent/CA2016150A1/en not_active Abandoned
  • 1990-05-07 ZA ZA903437A patent/ZA903437B/xx unknown
  • 1990-05-08 JP JP2116997A patent/JPH02305982A/ja active Pending
  • 1990-05-08 EP EP90304952A patent/EP0397454A1/en not_active Withdrawn

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