JPS6389686A - Anticorrosive for soft water boiler - Google Patents

Abstract

PURPOSE:To provide an anticorrosive capable of stably preventing the corrosion of the steel parts of a soft water boiler by using a mixture of an ascorbate and/or an erythorbate with monosaccharides as an effective component. CONSTITUTION:A water soluble ascorbate and/or a water soluble erythorbate is mixed with monosaccharides such as glucose, mannose and galactose to prepare an anticorrosive for a soft water boiler. The water soluble salt is of an alkali metal base or an org. base. A proper amount of the anticorrosive is added to river water or the like. The anticorrosive forms a corrosion preventing film considered to be a kind of magnetite film on the metal surface of a boiler at the service temp. and pressure of the boiler by the synergistic effect of the components. The film is dense and can protect the metal surface in a corrosive environment at high temp. and pressure.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is used in boilers that use soft water such as industrial water when operating at relatively high temperatures and high loads, and is used in steam generators, heat exchangers, etc. It relates to anticorrosive agents used to prevent corrosion of metals such as metals, especially steel.

[Conventional technology]

This is because soft water boilers use water that contains interfering ions, such as chlorine ions, sulfate ions, nitrate ions, and carbonate ions, which promote corrosion of metals.

Corrosion of metals is always a problem. In particular, in recent years, there has been a trend to operate boilers more efficiently, such as operating at higher temperatures and higher loads, and operating with higher concentration of water. For this reason, naturally, the corrosion accelerating effect due to high temperatures increases, and the corrosion accelerating effect occurs due to the concentration of interfering ions in the boiler water, and these synergistic effects significantly increase corrosion, and in some cases, the boiler may be fatally damaged. This will cause corrosion problems.

In order to prevent these corrosions, conventional methods include the addition of oxygen scavengers such as hydrazine and sulfites, molybdates, tungstates, and polymeric phosphates.

Inorganic and organic compounds such as gluconate, tartrate, tannin, and lignosulfonate have been used alone or in combination as anticorrosive agents.

[Problem that the invention seeks to solve]

However, hydrazine is highly toxic, and sulfite has the drawback of generating sulfate, which is an interfering ion, as a result of its deoxidizing action. Furthermore, since it is necessary to always add an appropriate amount of these to water using a collection pump, a very complicated process is required in terms of management.

Additionally, molybdates, tungstates.

Polymer phosphates, gluconates, tartrates, tannins, lignin sulfonates, etc. generally have poor anticorrosion effects;
A drawback is that water quality with a high concentration of interfering ions tends to cause pitting. In particular, phosphates are the main cause of red tides due to eutrophication in ocean areas.

This led to wastewater pollution.

[Means for solving problems]

In view of the above problems, the present invention is based on sodium.

Salts of alkali metal bases such as potassium, organic bases such as monoethanolamine, jetanolamine, and ammonia, and water-soluble ascorbate or erythorbate, either alone, and glycose, mannose, galactose, or fructose.

It was mixed with monotri such as arabinose xylose.

Alternatively, an anticorrosive agent for soft water boilers is provided, which is a mixture of ascorbate and erythorbate and a monosaccharide.

In addition, ascorbate, erythorbate and monosaccharide can be used regardless of isomer, and the mixing ratio of ascorbate, erythorbate and monosaccharide is 1 weight ratio, 99
F1~1:99. Preferably.

5:95-50:50 is good.

Additionally, polyacrylates, polymaleates.

Scale dispersants such as morpholine and manoethanol.

Auxiliary anticorrosive agents, antifoaming agents, alkaline agents such as caustic soda and ammonia can also be added to the water for use in combination.

[Effect]

Due to the synergistic effect of each component of the anticorrosive agent of the present invention, a black anticorrosive film, which is considered to be a type of magnetite film, is formed on the metal surface at the operating temperature and pressure of the boiler, and this film is extremely dense.

It is thought to protect metal surfaces in corrosive environments at high temperatures and pressures.

〔Example〕

An anticorrosive solution prepared by adding an anticorrosive agent according to the present invention to tap water having the analytical values shown in Table 1 was added to an autoclave having an internal volume of 11 and then 2 test pieces (structural steel materials, JIS- Z-3101, 2 types, 5S-4
1.35 x 50 x 1.2 (mm)) was immersed in the anticorrosive solution.

Table 1 Water analysis values The autoclave was heated to a temperature of 180±5"C and left to stand for 2 days. After 2 days, the autoclave was cooled.
Take out the test piece and observe the presence or absence of rust,
Corrosion products are treated with hydrochloric acid (10% aqueous solution, inhibitor added)
After removing it inside, wash it with water.

Impressions were made and the weight of the test piece was measured, and the weight loss before and after the test was calculated as the daily weight loss per unit area.

The MDD value (mg/dcm''/day) was calculated.

In addition, the anticorrosive agent according to the present invention is as follows.

Example 1: Mixture of ascorbic acid sodium salt and glycose (weight ratio 10:90) Example 2: Mixture of ascorbic acid triethanolamine salt and glycose (weight ratio 2:98) Example 3: Ascorbate sodium salt, erythorbine Mixture of acid ammonium salt and fructose (weight ratio 20:20: Example 4
: A mixture of erythorbic acid potassium salt and glycose (weight ratio 70:30) was used.

In contrast, as a comparative example.

Comparative example 1: Ascorbate sodium salt Comparative example 2; Ascorbate triethanolamine salt Comparative example 3: Erythorbic acid potassium salt Comparative example 4: Erythorbic acid ammonium salt Comparative example 5: Glyose comparative example 6: Fructose Comparative example 7: No addition Comparative example 8: Sodium molybdate salt Comparative example 9 Sodium nigerconate salt Comparative example 10: Sodium hexametaphosphate salt Comparative example 11;
Lignosulfonic acid sodium salt was used.

The anticorrosion effects of Examples and Comparative Examples are shown in Table 2.

Table 2 with blank space below Note: Concentration of anticorrosion agent added: 600 ppm From the test results in Table 2, it can be seen that the anticorrosion agent according to the present invention is effective in preventing corrosion of metals.

〔Effect of the invention〕

The anticorrosive agent of the present invention forms a visible strong film on the metal surface, exhibits stable anticorrosion ability, and has superior anticorrosion effect compared to conventional agents. Additionally, no special management such as oxygen absorbers is required, and corrosion problems caused by management errors can be completely prevented.

Claims (1)

[Claims] An anticorrosive agent for soft water boilers, characterized in that it is a mixture of at least one of ascorbate and erythorbate and a monosaccharide.