JPS6312941B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for preventing corrosion of metal surfaces in cooling water, boiler water, and other water systems. Today, phosphorus-containing compounds such as condensed phosphates, phosphonocarboxylic acids, and phosphoric esters are used as corrosion and scale inhibitors for metal surfaces in cooling water systems, boiler water systems, and the like. These phosphorus-containing compounds have been used today as an alternative to highly toxic chromium-based chemicals, but if blow water such as cooling water or boiler water containing these chemicals is released into inland seas, seawater It is said that eutrophication occurs and promotes the occurrence of red tide. Therefore, recently it has been proposed to use chemicals that do not contain chromium compounds or phosphorus-containing compounds, but at present they have not been found to be sufficiently effective in preventing corrosion. The purpose of the present invention is to improve the drawbacks of conventional anticorrosive agents as described above, by selecting a specific substance from among water-soluble polymer compounds that do not correspond to chromium compounds or phosphorus compounds. As a result of combining magnetic field treatment in the presence of calcium ions, an effective anticorrosive effect on underwater metal surfaces was discovered, and the present invention was constructed. That is, the present invention provides one or more water-soluble monomers having an ethylenically unsaturated bond and a carboxyl group in water, and/or a monomer having an ethylenically unsaturated bond and a sulfonic acid group as a main structural unit. This method is characterized by adding a magnetic polymer compound and performing magnetic field treatment in the presence of calcium ions. The present invention will be explained in detail below. Recently, various water-soluble polymer compounds (hereinafter simply referred to as polymer compounds) have been used as agents other than chromium-based agents or phosphorus-containing compounds in cooling water, boiler water systems, etc. However, these polymer compounds mainly serve to prevent calcium scale from adhering to metal surfaces or to promote softening of the scale itself, and their anticorrosion effects cannot be seen in practice. On the other hand, magnetic field treatment of water has long been known as a method for preventing scale adhesion without adding chemicals, but although this treatment method has a certain degree of scale softening effect, it can be said that it has almost no anti-corrosion effect. The present invention is characterized in that by adding a certain kind of substance as a polymer compound to water and treating the water with a magnetic field in the presence of calcium ions, it achieves an extremely excellent effect in preventing corrosion of metal surfaces underwater. be. The polymer compound used in the present invention is one or more types whose main structural unit is a monomer having an ethylenically unsaturated bond and a carboxyl group, and/or a monomer having an ethylenically unsaturated bond and a sulfonic acid group. Among the monomers of the former, there are acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid, etc., and acrylic acid and methacrylic acid are particularly effective. Examples of the latter monomer include acrylamide methylpropylene sulfonic acid and methacryloylpropylsulfonic acid. The former monomer also includes copolymers such as acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, hydroxyethyl acrylate, hydroxypropyl acrylate, and hydroxyethyl methacrylate. The molecular weight of these polymer compounds is 2000~
A range of 20000 is particularly effective, and specific examples include polyacrylic acid (molecular weight 2000), acrylic acid/hydroxyethyl acrylate (weight ratio 7:3, molecular weight 7000), methacrylic acid/acrylamidomethylpropylsulfonic acid (Weight ratio 1:
1, molecular weight 10,000), methacrylic acid/methacryloylpropylsulfonic acid (weight ratio 2:1, molecular weight 8,000), and methacryloylpropylsulfonic acid (molecular weight 2,000). The amount of these polymer compounds added in the present invention is usually
It is preferable to set it in the range of 10mg/~100mg/. In addition to the above-mentioned polymer compounds, chemicals to be added to the water include known anticorrosive agents such as phosphorus-containing compounds such as polymerized phosphates, phosphonocarboxylic acids, phosphonic acids, and phosphoric acid esters, or malic acid, tartaric acid, and glucone. Oxycarboxylic acids such as acids, aliphatic carboxylic acids such as caprylic acid, capric acid, and lauric acid, azole such as triazole and imidazole, phytic acid, polyvalent metal salts such as nickel, aluminum, and zinc, borax, Can be used in combination with silicates etc. Next, when these polymer compounds are added to water and subjected to magnetic field treatment, it is preferable that calcium ions coexist in the water in order to further enhance the anticorrosion effect. The amount of calcium ions present in general tap water and industrial water, for example around 20mgCaCO ₃ , has an effect, but
Most preferred is a range of 50 to 300 mg CaCO ₃ /. The present invention adds these polymer compounds to water and performs magnetic field treatment in the presence of calcium ions, but the magnetic field treatment device used in the present invention has a structure in which water passes through a space in which a magnetic field is formed. Any product will do, but one example is Hako Water Conditioner (USA, Introdel).
Incorporated) is suitable. Note that a so-called electromagnetic filter can also be used. Appropriately, the strength of the magnetic field is 2000 Gauss or more, and the contact time in the magnetic field treatment device is 1 to 10 seconds. The magnetic field treatment device may be attached directly to the circulating cooling water piping to allow water to flow through it, or may be attached to this bypass path by bypassing a portion of the circulating cooling water, or may be attached to the make-up water piping of the circulating cooling water system. It may be attached to the department. Examples will be described below to further clarify the effects of the present invention. Example An open circulation cooling water system with a cooling tower as shown in the drawing was installed, and a model heat exchanger with an STB-35 tube with a total length of 3 m, an outer diameter of 19 mm, and an inner diameter of 16 mm was installed in the system. Circulating water is flowing, and the temperature at the inlet of the heat exchanger of the circulating water is 30℃, and the temperature at the outlet is 30℃.
Steam was passed through the shell side of the heat exchanger to a temperature of 50°C. An SS-41 test piece with a width of 20 mm, a length of 50 mm, and a thickness of 1.5 mm was attached to the circulating water on the outlet side of the heat exchanger tube. Also, in terms of average water quality,
PH7.1, M-alkalinity _30mgCaCO3 /, calcium hardness _50mgCaCO3 /, chlorine ion 20mgCl/
, tap water with an electrical conductivity of 180 μS/cm was used as makeup water. The magnetic field treatment device was attached to a bypass path provided in the circulating water line just before entering the heat exchanger. Magnetic field processing equipment is manufactured by Introdel in the US,
Hako Water Conditioner by Incorporated
Model 115 was used. The test period was 30 days, and at the start of the test, the circulating water tank was filled with cooling water of the above-mentioned quality that had been concentrated 6 times. Polymer compounds as shown in Experimental Examples 1, 2, and 3 of the method of the present invention were added to the lower storage tank of the cooling tower, and the circulating water was treated with a magnetic field to observe the corrosion rate of the test piece and the surface of the tube. In addition, as a conventional method, a method in which the same polymer compound used in Experimental Examples 1, 2, and 3 was added but no magnetic field treatment was performed, and a method in which only a magnetic field treatment was performed without adding a polymer compound were compared. I did it as an example. The above results are shown in Table 1. Experimental example 1 Sodium polyacrylate (molecular weight 5000) Addition amount: 50mg/ Experimental example 2 Methacrylic acid/methacrylamidomethylpropylsulfonic acid (polymerization ratio 1:1, molecular weight 10000) Addition amount: 20mg/ Experimental example 3 Methacryloylpropyl Sulfonic acid (molecular weight
2000) Amount added: 20mg/ Comparative Example 1 Sodium polyacrylate (molecular weight 5000) Addition amount: 50mg/ However, without magnetic field treatment. Comparative Example 2 Methacrylic acid/methacrylamidomethylpropylsulfonic acid (polymerization ratio 1:1, molecular weight 10000) Addition amount: 20 mg/However, no magnetic field treatment was performed. Comparative Example 3 Methacryloylpropylsulfonic acid (molecular weight
2000) Addition amount: 20mg/ However, without magnetic field treatment. Comparative Example 4 No chemicals were added and only magnetic field treatment was performed.

[Table] As seen in Table 1, the present invention showed excellent anticorrosion effects.

[Brief explanation of the drawing]

The drawing is an explanatory diagram showing the flow of an open circulation cooling water system used when measuring the anticorrosion effects of the present invention and the conventional method.

Claims (1)

[Claims] 1 One or more water-soluble polymer compounds whose main structural unit is a monomer having an ethylenically unsaturated bond and a carboxyl group in water and/or a monomer having an ethylenically unsaturated bond and a sulfonic acid group. A method for preventing corrosion of metals in water, which is characterized by adding calcium ions and treating them with a magnetic field in the presence of calcium ions.