JPS5827986A - Corrosion inhibiting agent for metal - Google Patents

Abstract

PURPOSE:To provide a non polluting corrosion inhibiting agent by consisting a copolymer of maleic acid and amylene and does not contain harmful metals such as Cr and phosphate. CONSTITUTION:As a corrosion inhibiting agent for metals in contact with water, a copolymer of maleic acid and amylene is used by direct addition to an object water system. The maleic acid may be maleic anhydride, and alpha-amylene (1- pentene), beta-amylene (2-pentene), etc. alone or mixture of isomers are usable. For example, the monomers providing the above-mentioned constituting units of a proper molar ratio are added into a suitable org. solvent, and a polymn. initiator such as peroxide is added thereto, and the mixture is heated, whereby the monomers can be polymerized. The resultant inhibiting agent is adaptable to all kinds of water quality such as pure water, soft water, tap water, industrial water or the like and the concn. of use is determined according to objects; in general, the use at about 5-500ppm is sufficiently effective. The preferable pH of the object water is generally about 6-13.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a corrosion inhibitor for metals comprising a copolymer of maleic acid and amidino. More specifically, it relates to a corrosion inhibitor for metals that come into contact with water.

Chromates and various phosphates are well known as corrosion inhibitors used in open and closed cooling water systems. However, because chromate is highly toxic, emission regulations are in place, and because monophosphate can cause red tide, it is not advisable to actively use it from an environmental standpoint.

Furthermore, ochynecarboxylic acids such as citric acid and tartaric acid, which are known corrosion inhibitors, are easily decomposed by microorganisms, making it difficult to maintain the corrosion inhibiting effect.

In order to solve the drawbacks of the conventional technology, the present inventors conducted intensive research with the aim of developing a non-polluting corrosion inhibitor that does not contain harmful metals such as chromium and phosphates, and as a result, they have developed one. The invention was completed.

That is, the present invention is a metal corrosion inhibitor characterized by containing a copolymer of maleic acid and amidino.

Maleic acid, which is a structural unit of the copolymer used in the present invention, may be maleic anhydride. Other structural units, amidino, include α-amylene (1-pentene), β-amylene (2-pentene), and γ-amylene (2-methyl-
■-butene), α-1so amylene (3-methyl-1-
However, in the present invention, only one isomer of these amidinos may be used, or It is also possible to use a mixture of From the viewpoint of reaction efficiency, it is preferable to use a mixture.

The copolymer used in the present invention can be synthesized by various methods. For example, polymerization can be carried out by adding a suitable molar ratio of the monomers serving as the constituent units to a suitable organic solvent, adding a polymerization initiator such as a peroxide, and heating the mixture to 11°C.

In the case of total copolymerization with maleic anhydride and amidino, 1
To the extent that the synthesized copolymer can be sufficiently water-soluble,
Hydrogenate using hydric acid and alkali. Of course, this copolymer may also contain water-soluble salts such as 1.1Jum ff-potassium, and2Enium.

The reaction molar ratio between maleic acid (or maleic anhydride) and amidino is not particularly limited as long as it is sufficiently water-soluble when added as a corrosion inhibitor, but is usually l:
It is l.

Moreover, the molecular weight of this synthetic copolymer is 200. (10
0 or less, preferably 1, or 500 to 50. (About 100.

The corrosion inhibitor of the present invention contains the above-mentioned copolymer as an active ingredient, and is used by being directly added to the target water system in the same way as conventional corrosion inhibitors.

The corrosion inhibitor of the present invention can be applied to all types of water such as pure water, soft water, tap water (3), and industrial water, and the concentration used is determined depending on the purpose, but in general, the active ingredient is 5 to 5. There is a light effect at 500M. In addition, there is no need to particularly adjust the pi-] range of the target water system, but in general, the pH
6-13, and the preferred pH is 6-10. Target water systems to which this corrosion inhibitor is applied include open and closed cooling water systems.

- In cooling water systems that use pure water or soft water, there are fewer dissolved salts, and this has a positive effect on the action and effect of the anticorrosive agent of the present invention, demonstrating superior anticorrosion effects compared to conventional corrosion inhibitors. That's preferable.

The corrosion inhibitor of the present invention is sufficiently effective against aqueous systems made of steel even when used alone.

When other metals are also used together, other corrosion inhibitors may be added as necessary, such as ochinecarboxylic acids, thiazoles such as mercaptobenzothiazole, azoles such as bentriazole, 7-chlorohexylamine, hydrazines, etc. (4) Argylamine, alkanolamine, polyamine fx
Water-soluble amines, imines such as enalenimine, hyrolidine, piperidine, hiberazine, and ketimine; organic compounds such as hydroxamic acids such as formhydroxamic acid, acetohydroxamic acid, and benzhydroxamic acid;
Nitrite.

Silicates, condensed-1 organic-various phosphates, Nto Y4,
It can also be used in combination with inorganic salts such as zinc salts, nickel salts, and molybdenum salts.

The present invention will be further explained below with reference to Examples.F)-1 The present invention is not limited thereto.

Example 1 Test liquid 1e showing each water quality shown in coating-1 was taken in a heater, a predetermined amount of the corrosion inhibitor of the present invention was added thereto, and the water temperature was lowered to 5.
It was kept in OC. A test piece made of mild steel was suspended from a stirring rod in this hooker, and the condition was maintained for 5 days while rotating at a rotational speed of 160 mm.

The corrosion inhibitors used are shown below.

A, copolymer hydrolyzate sodium salt of maleic acid-amylene (mixture) (mole ratio l:1. average molecular weight approximately 3000) B, maleic acid-amidino (mixture) copolymer hydrolyzate sodium salt (mole Ratio ■: 1. Average molecular weight approximately 6500) For comparison, a. Sodium polyacrylate (average molecular weight approximately 4500
) b. Maleic acid-impterene copolymer hydrolyzate sodium salt (mole ratio': lt average molecular weight approximately 6000) was also tested.

The results are shown in Table-2.

In Table 1, the water system 1 corresponds to a closed cooling water system and a low concentration open cooling water system, and the water system 2 corresponds to an approximately 3 times concentrated open cooling water system.

Table - ■ Table - 2 (7) From these results, it can be seen that the corrosion inhibitor of the present invention has a far more corrosion inhibiting effect than the chemicals shown for comparison.

Example 2 A corrosion test was conducted under the same conditions as Example 1 except that pure water with a conductivity of 1/1 s/cm or less was used.

The results are shown in Table-3.

Table 3 From these results, it can be seen that the corrosion inhibitor of the present invention exhibits superior corrosion prevention effects compared to conventional corrosion inhibitors even in pure water systems with extremely low salt concentrations.

Percentage Applicant: Kurita Industries Co., Ltd. (8) 49

Claims (1)

[Claims] A metal corrosion inhibitor characterized by containing a copolymer of maleic acid and amidino.