RU2108408C1 - Method for production of metal corrosion inhibitor - Google Patents

Abstract

FIELD: protection from corrosion; may be used in various industries. SUBSTANCE: method involves reaction of hexamethylene diamine with phosphoric acid and carbamide in the presence of glycerin. Reagents are used in the following more ratio: hexamethylene diamine:phosphoric acid:carbamide: : glycerin = 1.0 : 0.67-2.0 : 2.0-2.5 : 0.2-0.5. Produced corrosion inhibitor in concentration of 25-100 mg/l provides for protective effect of 83-99% in natural water with total salt content of 200 ml/l. EFFECT: higher efficiency. 2 tbl

Description

 The invention relates to the field of corrosion protection and can be used in various industries to protect metal aggregates and equipment from corrosion damage. An effective method of combating corrosion is the use of corrosion inhibitors. These substances are introduced into the corrosive medium in a small amount and, as a rule, modify the surface of the metal, preventing the flow of electrochemical reactions with its participation [1 and 2]. The use of inorganic reagents (polyphosphates, phosphates, chromates, nitrates, nitrites, silicates, borates, vanadates and other salts of alkali or alkaline earth metals) as inhibitors leads to the introduction of often highly toxic reagents or reagents that cause the development of microorganisms and algae in a corrosive environment [ 3].

The use of organic corrosion inhibitors turned out to be a more advanced and flexible method [2, 4, 5]. As inhibitors, organic compounds (or mixtures thereof) containing nitrogen, oxygen, sulfur, phosphorus and other functional groups are used. The production and range of organic inhibitors is expanding from year to year. The disadvantages of using organic inhibitors are:
1. Obtaining certain inhibitors is time-consuming and multi-stage, based on expensive and inaccessible raw materials.

 2. Some organic inhibitors are highly toxic, have a negative impact on the environment.

 3. Under the influence of water and air oxygen, many organic reagents undergo various chemical transformations, due to which their protective effect decreases, and new, sometimes toxic products appear.

 4. A number of compounds used as inhibitors contribute to the development of microorganisms and algae and, thereby, cause the appearance of biofouling on the surface and provoke biocorrosion.

 5. Some organic inhibitors cannot be used in chlorinated water, in water with a high content of chlorine and calcium ions, in acidic or alkaline environments.

 6. Low molecular weight polyfunctional organic compounds, protecting ferrous metals, enhance the corrosion of some non-ferrous metals and alloys, apparently due to the formation of complex compounds.

 These and some other reasons lead to the constant creation of new corrosion inhibitors.

 In the literature there is information about the creation of corrosion inhibitors based on hexamethylenediamine. So, hexamethylenediamine chromate is used as a passivator [6]. However, such a reagent is very highly toxic to higher plants and animals. A mixture of hexamethylenediamine and sodium nitrite can be used to inhibit corrosion in water circulation systems [7]. However, this mixture also has the above disadvantages - toxicity (hexamethylenediamine), initiation of biofouling (sodium nitrite), etc.

A known method of producing a corrosion inhibitor based on the condensation of hexamethylenediamine with alkyl phenols (RC ₆ H ₄ OH) and formaldehydes [8] (prototype). To implement this method, the reagents are mixed in an equimolar ratio, then the mixture is heated for 1 hour at 100-105 ^o C and the reaction product RC ₆ H ₃ (OH) CH ₂ ) ₆ NH is isolated by steam distillation and used as a corrosion inhibitor in the system electrolyte / oil in the presence of hydrogen sulfide.

Despite the high yield of the product, the prototype method has a number of significant disadvantages:
1. All reagents used are highly toxic substances. Therefore, if they remain unreacted, (for example, if stoichiometry is violated, mixing is bad, overheating, etc.) they form highly toxic waste.

 2. The process of obtaining an inhibitor requires steam distillation, which is highly energy intensive and leads to the formation of large amounts of wastewater.

 3. Obtaining corrosion inhibitors are poorly soluble in water, therefore, have limited use. For example, they cannot be used in water circulation systems.

 4. The starting alkyl phenols are relatively expensive and difficult to access reagents.

 The purpose of the proposed technical solution is to develop a method for producing a metal corrosion inhibitor with a high protective effect using more accessible reagents.

 This goal is achieved by the interaction of hexamethylenediamine with phosphoric acid and urea in the presence of glycerol. As a result of the reaction, a glassy polymer product is formed which is soluble in water and has an inhibitory effect. The reagents used are most appropriate to use in the following ratio (mol): hexamethylenediamine: phosphoric acid: urea: glycerin = 1: 0.67 - 2: 2 - 2.5: 0.2 - 0.5. The structure of the obtained polymer is not clearly established. Judging by the IR spectrum (KBr tablets), the polymer contains urea and guanidine groups, methylene and methine fragments.

 In the absence of glycerol (or its lack), a polymer is obtained that is insoluble in water. The solubility of the polymer also decreases with a decrease in the content of urea and phosphoric acid. Excess glycerol leads to an increase in reaction time and to obtain a product with a lower inhibitory effect. A large excess of urea and phosphoric acid leads to an excessive consumption of reagents and gives a decrease in the inhibitory effect of the product.

The developed method has the following advantages:
1. The only highly toxic reagent in this method is hexamethylenediamine, which is used in such a ratio with other reagents (in particular, urea) that ensures its complete conversion. Thus, the method does not provide for the formation of toxic waste.

 2. The process for producing an inhibitor is one-stage and does not require additional equipment (except for reaction).

 3. Urea, glycerin and phosphoric acid are affordable, reasonably cheap, multi-tonnage products.

 4. The resulting corrosion inhibitor is highly soluble in water, and therefore can be used in water circulation systems.

 The implementation of the method for producing a metal corrosion inhibitor is shown in the following examples.

Example 1. 11.6 g (0.1 mol) of hexamethylenediamine and 17.6 g (0.18 mol) of phosphoric acid and 2.76 g (0.03 mol) of glycerol were placed in a 100 cm ³ round bottom flask equipped with a stirrer and a reagent inlet. The resulting mixture was heated to form a homogeneous liquid mixture and 13.2 g (0.22 mol) of urea were added with stirring. Then the mixture was heated until the gas evolution ceased and a homogeneous mass was obtained (1.5 hours, 130 ^° C.). Upon cooling, the reaction mass solidified. Received 40.3 g of a glassy polymer with a melting point of 130-180 ^o C (above 180 ^o C decomposition is observed). Elemental analysis satisfactorily meets the gross formula:
C ₉ H ₁₉ N ₄ O • 1.5 H ₃ PO ₄ .

 In the table. 1, the resulting polymer is designated as sample No. 1 for corrosion testing. Similarly, inhibitor samples were obtained at different ratios of reagents (table. 1).

The use of the obtained polymer samples as corrosion inhibitors was tested on samples of steel St-10, size 10x50x1.5 mm, which, sanded and degreased (using toluene and ethanol), were sewn into a mixed corrosive medium (volume 1 l). Tap water with a pH of 7 and a total salinity of 200 mg / L was used as a corrosive medium. The test time of 120 hours, a temperature of 20 ^o C. In the absence of an inhibitor, the corrosion rate was 0.35 mm / year. The test results of the inhibitors are presented in table. 2.

Thus, a method for producing a metal corrosion inhibitor, which is easily implemented in practice, is based on available reagents, and the resulting product has a high protective effect at a concentration in the corrosive medium of 25-100 mg / dm ³ . Considering that the obtained polymer contains guanidine functions, one can expect additional biocidal activity for it [12 and 13].

 Used sources.

 1. Zhuk N.P. The course of the theory of corrosion and metal protection. M .: Metallurgy, 1976, p. 492.

 2. Akolzin A.P. Corrosion protection steel film former. M .: Metallurgy, 1989, p. 192.

 3. Tow Yu.I. etc. Corrosion protection of water-cooled equipment. Overview information. NIITEkhim. M .: 1979.

 4. Bregman J. Corrosion inhibitors. M .: Chemistry, 1966.

 5. Robinson D.S. Corrosion inhibitors. M .: Metallurgy, 1983, p. 272.

 6. Shekhter Yu.N. Protection of metals from corrosion. M-L .: Chemistry, 1964, p. 20.

 7. Tsvetkov VV et al. Inhibition of metal corrosion in recirculating water use systems. Chemical Pharmaceutical Journal. 1994, N 5, p. 50.

 8. Abdulaev G.K., Farkhadova S.M., Agamaliev E.A. A method of obtaining a corrosion inhibitor. USSR author's certificate N 164513, 1964.

 9. Malysheva L.F. et al. Photometric determination of certain fungicidal substances with guanidine function in water. Factory Laboratory, 1985, p. 3.

 10. Chemical Encyclopedia Vol. 3, Publishing House Big Russian Encyclopedia M., T. 1992, p. 1239.

Claims (1)

 A method of producing a metal corrosion inhibitor based on hexamethylenediamine, characterized in that the reaction of hexamethylenediamine with phosphoric acid and urea is carried out by heating in the presence of glycerol in the following ratio of moles: mol: hexamethylenediamine: phosphoric acid: urea: glycerol = 1: 0.67 - 2: 2 - 2.5: 0.2 - 0.5.

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