JPS6217191A - Method and composition for preventing formation of scale andcorrosion - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to methods and compositions 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 the system, when used in circulating or single-pass systems, after exposure to or saturation with air, it becomes corrosive to the metal surfaces it comes in contact with. Furthermore, when water is used in a circulation system for concentrating dissolved salts, metal salts such as calcium and magnesium, which are unique to the particular water, deposit on metal surfaces and form scales. The presence of scale on metal surfaces impedes the heat transfer properties of the metal and reduces 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 gold R used in the device is various, 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.

(Problem to be solved by the invention) The objective is to improve the effectiveness of such metal corrosion inhibitors.

SUMMARY OF THE INVENTION 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 that complexes the zinc. and a source of orthophosphoric acid ions are added to industrial water in combination, (a) the weight ratio of zinc to zinc complexing polymer is in the range of about 1:1 to about 1=25, and (b) the zinc to The weight ratio of orinphosphate ions is approximately 2=
(c) the zinc complexing agent has a weight average molecular weight of about 500 to about 1:10;
25.000, polyacrylic acid or acrylic acid/
Acrylic acid lower alkyl ester copolymer, or
A mixture of these, this co-4 remer is acrylic acid 40
This is a method for preventing metal corrosion and scale formation in which the lower alkyl acrylate is ethyl acrylate or methyl acrylate.

In a further preferred embodiment, the zinc-complexing polymer is first combined with a zinc salt to form a zinc/polymer complex, with the zinc content being 0.5 to 5 pprn and the polymer being 0.5 to 125 pprn.
m to corrosive water containing or-11phosphate ions. Another preferred embodiment provides that all three components are in the above ratio when added to the industrial water either simultaneously or separately i.e. in a single preparation or as separate preparations, and and the complexing polymer is made to have the above-mentioned 4 degrees.

(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 of the components, that is, the complexing polymer, zinc chloride, or The holes achieve a greater effect than that obtained when two of these three 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/lower alkyl acrylic varnish 7-A/:lf reamer. Preferred copolymers are those containing about 50 to 99 moles of acrylic acid and about 1 to 5 moles of acrylic acid lower alkyl ester. The most preferred copolymers include acrylic acid and ethyl acrylate, with 50-90% by weight of acrylic acid;
Furthermore, it is preferred that the copolymer contains 80±10% by weight of acrylic acid.

Using known polymerization methods, the molecular weight of the homopolymer or copolymer should be between 500 and 25,000. Preferred copolymers of the invention have a molecular weight of about 1,000.
~10,000, and the most preferred molecular weight of the homopolymer or copolymer of acrylic acid is about 1,500.
~7,500.

As mentioned above, the copolymers are prepared using aqueous polymerization techniques. This polymerization is accomplished by adding a sufficient amount of a water-soluble base, e.g., an alkali metal hydroxide such as sodium or potassium hydroxide, to maintain the - of the copolymer between about 2.0 and 9.0 during its preparation and thereafter. is necessary, and 3.0 to 5.0 is preferable.

The copolymer was polymerized in the usual manner to a concentration of 20 to 80%.
Polymer solution of This solution is diluted to the desired concentration before or after forming the copolymer zinc complex.

Polymers can also be used one in combination with the other, i.e. homopolymers of acrylic acid are combined with acrylic acid alkyl esters/acrylic acid copolymers to form zinc complexes in circulating industrial water. The results necessary to act effectively as a corrosion and/or scale inhibitor can be achieved.

Preparation of Zinc/Copolymer Complexes Zinc complexes of acrylic acid containing zinc and a complexing polymer can be easily prepared. A water-soluble zinc salt, such as zinc chloride, zinc sulfate, or zinc acetate, is added to the preformed polymer solution at a weight ratio of polymer to zinc ion of about 1:1 to 25:1. The preferred weight ratio is 2:1-1
The ratio is 0:1.

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 prepared by the zinc/copolymer complex is acidic, but the zinc salt, the complexing polymer, and the orthophosphate ion source are used to prepare the nine compositions.
can be from about 2.0 to about 13.5. When the pH is high, it is necessary to maintain stability by increasing the weight ratio of Prima to zinc. When the pH is above 7.0, it is preferred that the weight ratio of Prima to zinc be from about 3:1 to 20:1.

Another preferred form of the invention is the use of a zinc/sulfur complex in combination with an effective amount of a water-soluble orthofluoric acid 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 in a type and amount that does not destabilize the complex when added to the zinc/copolymer composition. When adding to the industrial water to be treated,
The orthophosphate ion source is selected from an inorganic orthophosphate ion source such as phosphoric acid or its water-soluble metal or ammonium salts. The combination of zinc/polymer complexes with or-11-phosphate ions provides additional protection for circulating or single-pass cooling water without corrosion or scale formation, and for controlling cooling water. The cooling effect can be achieved without the need to add ingredients.

As mentioned above, industrial water to be treated with a combination of zinc/polymer complex and ortho]phosphate ions can be applied industrially as cooling water or heating water even when it is passed through once instead of being circulated. can.

Although particularly useful in recirculating systems, single-pass cooling is commonly used, ie, introducing water into equipment requiring cooling, passing the water through the system once, and then 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 the cooling tower for use. However, to be effective, the zinc/polymer complex must be used in combination with orthophosphate ions in water at a pH of about 7.5-9.5.

Such industrial water usually has a concentration of 100 to 1,000 ppm.
It has a calcium hardness including calcium carbonate.

Furthermore, such water usually has a magnesium hardness of 100 to 1,000 ppm, measured as magnesium carbonate, and an M-alkalinity measured as calcium carbonate, that is, about 50 to 1,000 ppm of calcium carbonate when methyl orange is used as an indicator. 500 ppm, and the conductivity is about 2
50 to 10,000 μmha.

Such industrial water typically has a temperature of about 24 to about 65 degrees Celsius (70 to 150 inches F) after passing through equipment that requires cooling.
), normal operating temperature is about 38~60℃ (lOO~140℃)
6F).

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/orthochlorate ion composition has a total zinc amount of about 0.5 to 5.0 ppm;
The weight ratio of zinc to polymer in industrial water is approximately 1:1.
to about 1:25, and the weight ratio of zinc to orthophosphate ions is about 2=1 to about 1:10. In order to increase the effectiveness,
Reduce the concentration of zinc contained in industrial water from about 1.0 to about 3.0 p
pm, and the weight ratio of zinc to polymer is about 1:1 to about 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, and most preferably about 1:4.

Compositions of zinc/polymer complexes and orthofluorinate ions can be used in combination with other materials commonly used in circulating water. For example, a composition of zinc/4-lima monocomplex and orthophosphate ion can be further combined with tolyltriazole,
Ingredients such as 1-hydroxy-ethyridine, 1-diphosphonic acid may also include other complexing organophosphonic acids such as 1-phosphonobutane-1,2,4-tricaldic acid. Corrosion protection is particularly improved when the composition of zinc/polymer complex and orthophosphate ions includes other components, 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 W&T held in Pittsburgh, Pennsylvania, November 4-6, 1975
Announced at the 38th Annual Pension of erConfsrence
A composition containing a complexing polymer, a zinc salt, an orthophosphoric acid ion source, and other ingredients was tested using the No. 4 Ilot cooling tower described in the C article. The water tested had a pH of 8
．． 0 to 9.0], the calcium hardness as calcium carbonate is about 300 to about 400 ppnn, and the magnesium hardness as calcium carbonate is about 150 to about 250 ppnn.
pm, and M-alkalinity is about 100 to about 300 ppm as calcium carbonate, and the conductivity is about 3,80 ppm.
It was 0 to about 4,200 μmho. Furthermore, this circulating water contains approximately 1,000 ppm of sulfate ions.

It contained about 250 ppm chloride ions and about 600 ppm sodium ions.

Below is kinpaku The active components listed 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 calculated from orthophosphate anions generated by adding a phosphate anion source. Indicates an acid ion. Each of these components is listed in Table 1.
It was present at active concentrations in pm. The lower part of Table 1 shows the corrosion results for mild steel heat exchange tubes with a heat exchange coefficient of about 1580 to about 4730 W/tn (about 500 to about 1,500 BUT/ft2/h) under these conditions for one year. The thickness of the lost mild steel is m1l (0,0254 tan) (hereinafter mp
y), and the formed scale is on the metal surface 18
It is calculated and shown based on the amount deposited per 6 crn2 (0.2 ft2) per day.

Column 1 shows a composition comprising 6 ppm of an acrylic acid/ethyl acrylate copolymer of a preferred molecular weight and 2 ppm of an acrylic acid homopolymer of a similarly preferred molecular weight in combination with 3 ppm of zinc. It was used for circulating water in a cooling tower and tested for a period of time with reproducible results. The corrosion results for the mild steel heat exchanger tubes were approximately 0.99 mm (approximately 39 ml) per year. This is too high to be acceptable.

At the same time, test results of deposits formed on this heat exchanger tube showed that using the above composition, a metal surface of approximately 186 cm2 (
Approximately 0.2 ft) was covered with 6151119 particles in one day, which is also not acceptable.

Column 2 of Table 1 used a combination of complexing tellimer and zinc with the usual organophosphate ions used as corrosion and scaling inhibitors. In the same water and same conditions trap as above, the corrosion results were 1.
48 ffla (59 mil), scale formation was 735 m9 deposited per day on 186 cm2 (0.2 ft2) Ic of metal surface.

Column 3 shows the results of combining the complexing polymer and zinc with 3 ppm of another common phosphonic acid-type corrosion inhibitor, 1-phosphonobutane-1°2.4-tricarthenic acid (PBTC), which also reduced the corrosion rate. 62 mpy, and the scale formation rate was 8511n9 on a metal surface of 186an2 (0.2ft2) for one day.

Other columns in Table 1 show various combinations of complexing polymers with zinc and/or orthophosphate ions.

Furthermore, 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 can be seen, the combinations of complexing polymer, zinc and orthophosphate ions all gave excellent results, with corrosion rates ranging from 1.4 to 11.8 mpy.
, and the scale formation rate depends on the metal surface 186 cm2 (0,2
ft2) per day. Some columns in Table 1 show only the combination of primer and orthophosphate ion, or only the combination of orthophosphate ion and zinc. Although these results show that the combination of zinc and phosphonate ions also improves results, in any case, excellent results can be obtained using the triple combination composition of the present 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 zinc/copolymer complexes.

The copolymer used was approximately 80% by weight of sodium acrylate, designated as acrylic acid, and approximately 2% by weight of ethyl acrylate.
It was an aqueous solution of 20 t, containing 0 heavy ff1fi. Note that the molecular weight of the copolymer was approximately 1,500.

This composition added the lid components shown in the following table to the copolymer solution.

Composition A Ingredient h Chico I Limer-5
5,0 Deionized water 19.5 Potassium hydroxide (45% active) 7.5 Zinc chloride (67% active) IS, O Mix the ingredients other than zinc chloride to make a homogeneous solution, and stir this thoroughly. while adding zinc chloride to form the zinc/copolymer complex of the present invention. The -4 of the solution was approximately 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 Ingredients Weight % copoly w-
45,8 Product name Mobay QC-20034,0 Deionized water
34.3 phosphoric acid (85ti activity) 9
．． 7 Zinc chloride (67% activity) 6.2 The voice of the solution is approximately 2.0, and the final product is heated to dissolve the commercially available azole copper corrosion inhibitor MobayOC-2003, a water-soluble copper corrosion inhibitor tolyltriazole. promoted.

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.

The following test method for evaluating the effect of whitening used a laboratory-scale cooling system. For more information about this device, please contact International Water Co.
nfe-relce (November 4-6, 1975, R
The Na
1c.

Chemical Company Nori, T, Ree
d, R, Na5s “Small -8cale”
Short-Term Methods of Eva
luating Coo mouth Water Trea
tments -Are They Worthwhile
le':''''.

This test apparatus was used to test Composition A against each component added individually to the test water. The characteristic values of the water in the test equipment were as follows.

p14 s, 4-8.8 alkalinity 90-216 calcium
330-410 magnesium
80-270 The three main components of the invention, either as a single composition or by adding the various components individually to the circulating water,
That is, eight tests were conducted using combinations of zinc, polymer, and orthophosphate ions.

As shown in Table 2, the total concentration of zinc is greater than 0.5 ppm, the ratio of zinc to polymer is 1=2 to 1:10°, preferably 1:4 to 1:5, and zinc to orthophosphate Favorable results have been obtained when the ion ratio is between about 1:2 and about 1:4.

Below 7:-white −〇

Claims (1)

[Claims] 1. A composition for preventing corrosion and scale formation in an aqueous system, comprising: an aqueous solution of a water-soluble zinc/polymer complex having a weight ratio of zinc to polymer of 1:1 to 1:25; containing a dissolved orthophosphate ion source with a weight ratio of zinc to orthophosphate ions of about 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/
an acrylic acid lower alkyl ester copolymer, or a mixture thereof, the copolymer having an acrylic acid content of about 40 to about 99 mole percent, 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 a water-soluble zinc salt, a zinc-complexing polymer, and orthophosphoric acid to the water; Adding a combination of effective amounts of ion sources and (a) providing a weight ratio of zinc to zinc-complexing polymer of about 1:1 to
(b) the weight ratio of zinc to orthophosphate ions is about 2:1 to about 1:25;
and (c) the complexing polymer has a weight average molecular weight of about 500 to about 1:10.
25,000 polyacrylic acid, or an acrylic acid/acrylic acid lower alkyl ester copolymer, or a mixture thereof, the copolymer contains 40 to 99 mole percent acrylic acid, and the acrylic acid lower alkyl ester is combined with ethyl acrylate. or methyl acrylate, a method for preventing corrosion and scale formation. 3. (a) The weight ratio of zinc to complexing polymer is about 1:1 to
(b) the weight ratio of zinc to orthophosphate ions is about 1:1 to about 1:8;
(c) The weight average molecular weight of the complexing polymer is about 1,000.
~10,000, and (d) adding an effective amount of a combination of a water-soluble zinc salt, a zinc-complexing polymer, and an orthophosphate ion source to the industrial water;
3. The method of claim 2, wherein the total concentration of zinc is about 1 to about 3 ppm. 4. A combination of an effective amount of a water-soluble zinc salt, a zinc complexing polymer, and a source of orthophosphate ions is added to industrial water as a single preparation containing the zinc salt, complexing polymer, and source of orthophosphate ions. In addition, the method according to claim 3. 5. A patent for adding a water-soluble zinc salt, a zinc-complexing polymer, and a source of orthophosphate ions to industrial water, each as components in separate preparations, and combining these components during exposure to industrial water. The method according to claim 3. 6. The method according to claim 2, wherein the industrial water is brought to a natural pH without adding any acid source other than an orthophosphate ion source. 7. The water-soluble zinc/polymer complex has a weight ratio of zinc to polymer of 1:1 to 1:8, and the zinc-complexing polymer has
The composition of claim 1, wherein the weight average molecular weight is about 1,000 to about 10,000, and 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.