JPH0140109B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method and composition for preventing metal corrosion and scale formation by industrial water. BACKGROUND OF THE INVENTION Many industrial applications require the use of aqueous solutions or water for a variety of purposes, such as heat exchangers, cooling towers, coolers, and other water-based heat transfer systems. As water comes into contact with the metal surfaces of this system,
When used in circulating or single-pass systems, after exposure to or saturation with air, it becomes corrosive to metal surfaces it comes into contact with. Furthermore, when water is used in a circulation system for concentrating dissolved salts, salts of metals such as calcium and magnesium, which are unique to the particular water, deposit on metal surfaces and form scales. If scale is present on the metal surface,
Interferes with the heat transfer properties of the metal, reducing the efficiency of the system. In addition, severe corrosion of the metal surface progresses under the scale. It is important to minimize scale deposition and corrosion of the metal surfaces of heat transfer products. To achieve this purpose, anti-corrosion and anti-scaling agents are added to the water. The metals used in the device are diverse, including iron in the form of steel, aluminum, copper, and copper alloys. Copper in ionic form dissolved in water is known to accelerate the corrosion of iron, and therefore many corrosion inhibitors contain copper chelators or copper inhibitors, such as tolyltriazole, to accelerate the corrosion of metals. Minimize further. (Problems to be Solved by the Invention) It is an object of the present invention to improve the effectiveness of such metal anticorrosive agents. (Means for Solving the Problems) The present invention provides a method for preventing corrosion and scale formation of metals exposed to industrial water, comprising: an effective amount of a water-soluble zinc salt; and a water-soluble polymer complexing the zinc. and an orthophosphate ion source and added to industrial water, (a) a weight ratio of zinc to zinc complexing polymer of about 1:
(b) a weight ratio of zinc to orthophosphate ions of about 2:1 to about 1:25;
(c) the zinc complexing agent has a weight average molecular weight of about 500 to about 1:10;
25000, polyacrylic acid or acrylic acid/lower alkyl acrylic ester copolymer, or a mixture thereof, which copolymer contains 40 to 99 mol% of acrylic acid, and the lower alkyl acrylate is combined with ethyl acrylate or acrylic acid. This is a method of preventing metal corrosion and scale formation using acid methyl. In a further preferred embodiment, the zinc-complexing polymer is first combined with a zinc salt to form a zinc/polymer complex, with 0.5-5 ppm zinc and 0.5-5 ppm polymer.
Add to corrosive water containing orthophosphate ions to a concentration of 125 ppm. Another preferred embodiment is such that all three components are in the above ratio when added to the industrial water simultaneously or separately, i.e. in a single preparation or in separate preparations, and the zinc and complexing Bring the polymer to the above concentration. (Effects of the Invention) When the anticorrosive agent of the present invention is added to a system in which corrosion and scale formation are to be prevented, each component, that is, a complexing polymer, one of zinc or an orthophosphate ion source, or one of these three Achieve an effect that is greater than the effect obtained when two of the two components are added in combination. Zinc Complexing Polymers These complexing polymers are prepared by conventional solution polymerization techniques involving water-soluble free radical catalysts. See, for example, the polymerization technique of US Pat. No. 4,196,272. The polymer can be an acrylic acid homopolymer or an acrylic acid/acrylic acid lower alkyl ester copolymer. Preferred copolymers are those containing about 50 to 99 mole percent acrylic acid and about 1 to 50 mole percent acrylic acid lower alkyl ester. A most preferred copolymer comprises acrylic acid and ethyl acrylate, with 50 to 90% by weight of acrylic acid, and more preferably the copolymer comprises 80±10% by weight of acrylic acid. The molecular weight of the homopolymer or copolymer should be between 500 and 25,000 using known polymerization methods. Preferred copolymers of the invention have a molecular weight of about
1,000 to 10,000, and the most preferred molecular weight of the homopolymer or copolymer of acrylic acid is approximately
1500-7500. As mentioned above, the copolymers are prepared using aqueous polymerization techniques. This polymerization is carried out by adding sufficient amounts of a water-soluble base, e.g.
It is necessary to keep the
is the preferred pH. The copolymer was polymerized as usual, with a concentration of 20
~80% polymer solution. This solution is diluted to the desired concentration before or after forming the copolymer zinc complex. The polymers can also be used one in combination with the other, i.e. a homopolymer of acrylic acid is combined with an acrylic acid alkyl ester/acrylic acid copolymer to form a zinc complex;
The results necessary to act effectively as a corrosion inhibitor and/or scale inhibitor in circulating industrial waters can be achieved. Preparation of Zinc/Copolymer Complexes Zinc complexes of acrylic acid containing zinc and complexing polymers are easily prepared. A water-soluble zinc salt, such as zinc chloride, zinc sulfate, or zinc acetate, is added to the preformed polymer solution to provide a weight ratio of polymer to zinc ion of about 1:1 to 25:1. The preferred weight ratio is 2:1 to 10:1. An aqueous solution of zinc/copolymer complex can also be synthesized by adding a polymer solution to an aqueous solution of zinc salt. As previously mentioned, the aqueous solution of the copolymer from which the zinc/copolymer complex is prepared has an acidic PH, whereas the composition prepared with the zinc salt, complexing polymer, and orthophosphate ion source has a PH of about 2.0 to about 13.5. can do. When the pH is high, the polymer to zinc weight ratio must also be high to maintain stability. PH is
Above 7.0, a weight ratio of polymer to zinc of about 3:1 to 20:1 is preferred. Miscellaneous A preferred form of the invention uses a zinc/polymer complex in combination with an effective amount of a water-soluble orthophosphate ion source. As orthophosphate ions, phosphoric acid may be added to the composition of the present invention beforehand, or a source of orthophosphate ions may be added separately to the industrial water to be treated to prevent corrosion and scale formation. The orthophosphate ion source should be of a type and amount that does not destabilize the complex when added to the zinc/copolymer composition. When added separately to the industrial water to be treated, the source of orthophosphate ions is chosen as an inorganic source of orthophosphate ions, such as phosphoric acid or its water-soluble metal or ammonium salts. Combining the zinc/polymer complex with orthophosphate ions provides additional benefits to circulating or single-pass cooling water without corrosion or scale formation, and to control the PH of the cooling water. A cooling effect can be achieved without the need to add ingredients. Treatment of circulating industrial water As mentioned above, industrial water to be treated with a combination of zinc/polymer complex and orthophosphate ions can be used industrially as cooling water or heating water even when it is not circulated but is passed through once. It can be applied to Although particularly useful in recirculating systems, single-pass cooling is also commonly practiced, ie, introducing water into equipment requiring cooling and passing the water through the system once before discharging it to the environment. It is the inventor's intention here that the term industrial water refers not only to water that is concentrated for circulation through a cooling tower, but also to water that is passed through and used once. However, to increase the effectiveness, the zinc/polymer complex can be combined with orthophosphate ions to
Must be used in water with a temperature of approximately 7.5 to 9.5. Such industrial water usually has a calcium hardness containing 100-1000 ppm calcium carbonate. moreover,
Typically such water has a magnesium hardness of 100 to 1000 ppm, measured as magnesium carbonate;
M-alkalinity measured as calcium carbonate, that is, calcium carbonate when methyl orange is used as an indicator, is approximately 50 to 500 ppm, and the conductivity is approximately
It is 250 to 10000 μmho. The temperature of such industrial water after passing through equipment that requires cooling is usually about 24 to about 65℃ (70 to 150〓), and the normal operating temperature is about 38 to 60℃ (100 to 140〓). Will. When these three components are combined and added to industrial water, the composition is in an amount effective to inhibit corrosion and prevent scale formation on a variety of metal surfaces exposed to industrial water to be treated. The effective amount of zinc/polymer/orthophosphate ion composition has a total zinc amount of about 0.5 to 5.0 ppm and a zinc to polymer weight ratio of about 1:1 to about 1:25 in the industrial water; The weight ratio of zinc to orthophosphate ions is approximately 2:
1 to about 1:10. To increase effectiveness, the concentration of zinc in the industrial water should be from about 1.0 to about 3.0 ppm, and the weight ratio of zinc to polymer should be from about 1:1 to about 1:1.
It is preferable to set it to 20. Preferably, the weight ratio of zinc to orthophosphate ions is from about 1:1 to about 1:5, more preferably about 1:4. Compositions of zinc/polymer complexes and orthophosphate ions can be used in combination with other materials commonly used in circulating water. For example, the composition of zinc/polymer complex and orthophosphate ion is
Additionally, components such as tolyltriazole, 1-hydroxy-ethyridine, 1-diphosphonic acid, or other complexing organophosphonic acids such as 1-phosphonobutane-1,2,4-tricarboxylic acid may also be included. When the composition of zinc/polymer complex and orthophosphate ion contains other components,
Corrosion protection is particularly improved, and the prevention of scale formation is at least as good and often improved in circulating industrial water. Examples are presented below to demonstrate the advantages of the invention. Example 1 International Water Conference held in Pittsburgh, Pennsylvania, November 4-6, 1975
Compositions containing a complexing polymer, a zinc salt, an orthophosphate ion source, and other ingredients were tested using a pilot cooling tower as described in a paper presented at the 38th Annual Meeting of the Conference. The water tested was
PH is 8.0 to 9.0, calcium hardness as calcium carbonate is approximately 300 to approximately 400 ppm, and magnesium hardness as calcium carbonate is approximately 150 to approximately
250ppm, and M-alkalinity is about 100 to about 300ppm as calcium carbonate, and the conductivity is about
It was 3800 to about 4200 μmho. Furthermore, this circulating water contains approximately 1000 ppm of sulfate ions and approximately 1000 ppm of chloride ions.
250 ppm, and about 600 ppm sodium ions.

【table】

[Table] Active amounts of the ingredients shown in Table 1 were added to this water.
Table 1 shows zinc calculated from zinc ions generated by adding a complexing polymer and water-soluble zinc salt, and orthophosphate ions calculated from orthophosphate anions generated by adding an orthophosphate anion source. show. Each of these components was present at the active concentrations shown in ppm in Table 1. At the bottom of Table 1, the heat exchange coefficient is approximately 1580~
Approximately 4730W/m ² (approximately 500 to 1500BUT/ft ² /h)
For a mild steel heat exchange tube, the corrosion results are as follows: Mild steel thickness mil (0.0254 mm) lost in one year under these conditions
(hereinafter referred to as mpy), and the scale formed is calculated in mg deposited per day per 186 cm ² (0.2 ft ² ) of metal surface. Column 1 shows the composition, with a preferred molecular weight acrylic acid/ethyl acrylate copolymer of 6 ppm;
Similarly preferred molecular weight acrylic acid homopolymers
This composition, containing 2 ppm of zinc in combination with 3 ppm of zinc, was used in the pilot cooling tower circulating water and tested for a period of time with reproducible results. The corrosion result for mild steel heat exchanger tubes is approximately 0.99mm (approximately 39mil) per year.
It was at a ratio of This is too high to be acceptable. At the same time, according to test results of deposits formed on this heat transfer tube, using the above composition, metal surfaces of approximately
615 mg was deposited on 186 cm ² (approximately 0.2 ft ² ) in one day, which is also not acceptable. Column 2 of Table 1 used a combination of complexing polymer and zinc with a common organophosphate ion used as a corrosion and scaling inhibitor. In the same water and under the same conditions as above, corrosion results were 1.48 mm (59 mils) per year and scale formation was 735 mg deposited per 186 cm ² (0.2 ft ² ) of metal surface per day. Column 3 lists complexing polymers and zinc as well as other common phosphonic acid type corrosion inhibitors, 1-phosphonobutane-
Results are shown for a combination of 3 ppm of 1,2,4-tricarboxylic acid (PBTC), which also had a corrosion rate of 62 mpy and a scale formation rate of 851 mg per 186 cm ² (0.2 ft ² ) of metal surface per day. Other columns in Table 1 show various combinations of complexing polymers with zinc and/or orthophosphate ions. The table also shows the results for combinations which, in addition to the complexing polymer, zinc and orthophosphate ions, also contain organophosphate ions, phosphate ions and/or tolyltriazole components. As is clear from the table, complexing polymer,
Combinations of zinc and orthophosphate ions all showed excellent results, with corrosion rates ranging from 1.4 to 11.8 mpy and scaling rates ranging from approximately 23 mg to 145 mg per 186 cm ² (0.2 ft ² ) of metal surface per day. Ta. Some columns in Table 1 show only the combination of polymer and orthophosphate ions, or only the combination of orthophosphate ions and zinc, and these results show improvements over the combination of zinc and phosphonate ions. However, surprisingly good results are obtained when using the triple combination composition of the invention. In addition to the results shown in Table 1, examples are provided that demonstrate the preparation of zinc/polymer complexes and the evaluation of this type of composition in a circulating aqueous system. Example 2 This example demonstrates the preparation of a zinc/copolymer complex.
The copolymer used contained about 80% by weight of sodium acrylate, designated as acrylic acid, and about 20% by weight of ethyl acrylate, and was a 20% aqueous solution. The molecular weight of the copolymer was approximately 1,500. The composition was prepared by adding the components to the copolymer solution in the amounts shown in the table below. Composition A Ingredients Weight % Copolymer 55.0 Deionized water 19.5 Potassium hydroxide (45% active) 7.5 Zinc chloride (67% active) 18.0 Mix the ingredients other than zinc chloride to form a homogeneous solution and stir thoroughly. while adding zinc chloride to form the zinc/copolymer complex of the present invention.
The pH of the solution was 3.7. This composition will be referred to as composition A hereinafter. Example 3 Composition B was prepared from the following ingredients in the same manner as in Example 1. Composition B Components Weight % Copolymer 45.8 Trade Name Mobay OC-2003 4.0 Deionized Water 34.3 Phosphoric Acid (85% active) 9.7 Zinc Chloride (67% active) 6.2 The pH of the solution is approximately 2.0 and the final product is heated do,
It promoted the dissolution of the commercially available azole copper corrosion inhibitor Mobay OC-2003, a water-soluble copper corrosion inhibitor tolyltriazole. In Examples 2 and 3, it is important that the zinc salt is dissolved in a solution containing all other ingredients except the zinc salt. If this is not the case, the complex will tend to form insoluble hydroxides. Evaluation of the anticorrosive effect of the compositions of the invention in circulating hydrogen The test method used a laboratory scale cooling system. For more information on this device please visit International Water
Nalco Conference (November 4-6, 1975, Pittsburgh, Pennsylvania)
DTReed of Chemical Company, “Small−Scale Short−Term Methods of R.Nass”
Evaluating Cooling Water Treatments…Are
Are they worth while? This test apparatus was used to test Composition A against each component added individually to the test water. The characteristics of the water in the test apparatus were as follows: PH 8.4-8.8 Alkalinity 90-216 Calcium 330-410 Magnesium 80-270 The three main components of the invention, namely zinc, polymer and Eight tests were conducted using combinations of orthophosphate ions.As shown in Table 2, the total concentration of zinc was 0.5 ppm.
more, the ratio of zinc to polymer is 1:2 to 1:
10, preferably from 1:4 to 1:5, and favorable results have been obtained when the ratio of zinc to orthophosphate ions is from about 1:2 to about 1:4.

【table】

Claims (1)

[Scope of Claims] 1. A composition for preventing corrosion and scale formation in an aqueous system, wherein an aqueous solution of a water-soluble zinc/polymer complex having a weight ratio of zinc to polymer of 1:1 to 1:25 is a water-soluble Contains a dissolved source of orthophosphate ions, with a weight ratio of zinc to orthophosphate ions of approximately 2:1.
to about 1:10, and the polymer has a molecular weight of about 500 to about 25,000 and is an acrylic acid homopolymer, or an acrylic acid/acrylic acid lower alkyl ester copolymer, or a mixture thereof; A composition having an acid content of about 40 to about 99 mol%, and the aqueous solution having a pH of about 2.0 to about 14.0. 2. A method for preventing corrosion and scale formation on metals exposed to industrial water having a pH of about 7.5 to about 9.5, the method comprising: adding to the water an effective amount of a water-soluble zinc salt, a zinc-complexing polymer, and a source of orthophosphate ions; (a) a weight ratio of zinc to zinc complexing polymer of about 1:
(b) a weight ratio of zinc to orthophosphate ions of about 2:1 to about 1:25;
1 to about 1:10, and (c) the complexing polymer has a weight average molecular weight of about 500.
~25,000 polyacrylic acid, or an acrylic acid/acrylic acid lower alkyl ester copolymer, or a mixture thereof, containing 40 to 99 mole percent acrylic acid, and containing acrylic acid lower alkyl ester to ethyl acrylate or acrylic acid lower alkyl ester. Method for preventing corrosion and scale formation using methyl acrylate. 3 (a) The weight ratio of zinc to complexing polymer is approximately 1:
(b) the weight ratio of zinc to orthophosphate ions is about 1:1 to about 1:8;
1 to about 1:5, and (c) the weight average molecular weight of the complexing polymer is about 1000 to about 1:5.
and (d) adding to the industrial water a combination of an effective amount of a water-soluble zinc salt, a zinc-complexing polymer, and an orthophosphate ion source to provide a total zinc concentration of about 1 to about 3 ppm. The method according to claim 2. 4. Adding an effective amount of a combination of a water-soluble zinc salt, a zinc complexing polymer, and an orthophosphate ion source to industrial water as a single preparation comprising the zinc salt, complexing polymer, and orthophosphate ion source. ,
The method according to claim 3. 5. A claim in which a water-soluble zinc salt, a zinc-complexing polymer, and a source of orthophosphate ions are each added to industrial water as components in separate preparations, and the components are combined during exposure to industrial water. The method described in item 3 within the scope of 6. The method according to claim 2, wherein the industrial water has a natural pH without adding any acid source other than an orthophosphate ion source. 7 The water-soluble zinc/polymer complex has a zinc to polymer weight ratio of 1:1 to 1:8, and the zinc complexing polymer has a weight average molecular weight of about 1000 to about 10000.
The composition according to claim 1, wherein the aqueous solution has a pH of about 3.0 to about 8.0. 8. The composition according to claim 1, which additionally contains tolyltriazole, an organophosphate ion source, a phosphonate ion source, a polyphosphate ion source, or a mixture thereof as another anticorrosive agent. 9. The composition according to claim 1, wherein the aqueous system is a circulating aqueous system.