RU2109847C1 - Preparation for complex protection of metals from corrosion, biofouling and scale - Google Patents

Abstract

FIELD: chemical, oil refining, chemical-and-pharmaceutical industries, mechanical and hydraulic engineering, in systems of open recirculation and closed process water supply. SUBSTANCE: used as inhibitor of corrosion, biofouling and scaling is hydroxyethylidenebiphosphonate of polyhexamethyleneguanidine. EFFECT: higher efficiency, low toxicity and easily-available reagents. 1 tbl

Description

 The invention relates to the protection of metals from corrosion, biofouling scaling and can be used in the chemical, oil refining, chemical-pharmaceutical, machine-building industry and in hydraulic engineering in systems of open recirculation and closed technical water supply.

 In the chemical, oil refining, chemical-pharmaceutical and other industries, the system of closed water cooling of plants and assemblies is widely used, which are mainly made of carbon and low alloy steels. At the same time, the combination of large volumes of water and elevated temperatures creates extremely favorable conditions for corrosion and biodeterioration (biofouling) of the internal surfaces of heat exchangers and pipelines, which degrades their performance and leads to the early failure of expensive equipment.

 To combat corrosion, a large number of inhibitors have been created and are used [1-3]. However, they all have a number of limitations and disadvantages that reduce their effectiveness. For example, well-known polyphosphates (cathodic inhibitors) in the presence of heavy metal ions (mainly calcium and zinc) form protective films on the surface of metals [1-4]. The disadvantage of these inhibitors is their low effectiveness in demineralized and softened water.

 It is also known to use nitrogenous bases such as amines, hydrazines, azoles, etc., which slow down the interaction of water and oxygen in the air with the metal surface and thereby inhibit corrosion processes [1-3]. However, these compounds are ineffective in open recirculation systems made of carbon steel, and are very expensive.

 Polyvinylimidazoles are highly effective corrosion inhibitors [5]. These compounds protect copper and its alloys well from corrosion, but their effect on ferrous metals has not been completely studied.

 The closest in technical essence to the claimed drug are drugs developed by the company "Kurita" and used worldwide, such as "Polikrin", "Kurita S-1030" and "Kurita T-2800 and P.3700" [6]. The use of these reagents in technological water supply and water treatment can significantly increase the life of the equipment without repair. However, these reagents have a number of significant drawbacks, which include their high cost, low stability, and most importantly, they are not complex preparations and should be used in a mixture. The reagents "Kurita R-3700 and S-1030" contain polyphosphates as the main ingredient and are corrosion inhibitors, and "Polycrin" inhibits biofouling.

,
где
n= 4-30.An object of the invention is to provide means for the comprehensive protection of equipment and pipelines against corrosion of fouling and scaling. This task is achieved by the fact that as an inhibitor of corrosion, biofouling and scaling, hydroxyethylidene biphosphate polyhexamethylene guanidine of the formula

,
Where
n = 4-30.

 The specified polymer is obtained from polyhexamethylene guanidine hydrochloride by sequential treatment of this salt with sodium ethylate, a solution of 1-hydroxyethylene-bis-phosphonic acid.

The obtained samples with a concentration of 5–100 mg / L were investigated to inhibit corrosion, scaling, and biofouling under conditions close to the operation of water circulation systems. Three times evaporated tap water with a total salt deposition of 150 mg / l and a Ca ⁺² ion content of 30 mg / l was used as a corrosive medium. The pH was measured by the pH method.

The invention is illustrated by examples, the results of which are presented in the table.
Example 1. A sample for testing the anticorrosive properties of polyhexamethylene guanidinium hydroxyethylidene bisphosphonate (GKN-1) was carefully ground and degreased by washing with toluene and ethanol. The pH of the aqueous solution of GKN 4.85 (at 20 mg / l of the sample and 1 g / l of NaCl). Corrosion inhibition was quantified by electrochemical methods according to [7,8]. The study was carried out using a PI-50-1M potentiostat, a PR-8 programmer, a LKD-004 recorder, an YES-1 electrochemical cell, a silver chloride comparison electrode and a working electrode (test sample) and CT20 with an area of 1 cm ² . The potential sweep rate was 0.2 mV / s, polarization + 300 mV. During the test, the polarization resistance was measured and increased within 24 hours. The corrosion current (Stern-Jiri method [7.8]), the density of which in A / m ^{2 is} proportional to the corrosion rate, was calculated from the polarization resistance value. In the absence of an inhibitor, the corrosion current for the used corrosive medium was 0.48 A / m ² .

Salt deposition was estimated gravimetrically using an electrochemical method in a setup similar to that described at a current density of 1 A / m ² under cathodic polarization conditions. The tests were carried out for 4 hours. Model water with a hardness of 2 mEq / l (Ca ⁺² ) was used as the medium. The effect of inhibition of scaling was evaluated using the methodology [9]. In the absence of the inhibitor under study, scaling was 300 g / m ² .

The biocidal test of the inhibitors was checked using tap water by estimating the number of bacteria in one cm ^{3 of} water according to the TTC test proposed by Kurita. In the absence of inhibitors for 24 hours at 25 ^o C the number of bacteria was 10 ⁸ tank / cm ³ .

 The test results of corrosion inhibitors, scaling and biodeterioration are presented in the table.

 Example 2. A sample for testing the anticorrosion properties of polyhexamethylene guanidine hydroxyethylidene bisphosphonate (GKN-2) was prepared analogously to Example 1. The pH of an aqueous solution of GKN-2 was 5.79 (at 20 mg / L sample and 1 g / L NaCl).

 The study of the inhibition of corrosion, scaling and biofouling was carried out analogously to example 1. The test results of corrosion inhibitors, scaling and biodeterioration are presented in the table.

 Example 3. A sample for testing the anticorrosion properties of polyhexamethylene guanidine hydroxyethylidene bisphosphonate (GKN-3) was prepared analogously to Example 1. The pH of an aqueous solution of GKN-3 was 7.09 (at 20 mg / L sample and 1 g / L NaCl).

 The study of the inhibition of corrosion, scaling and biofouling was carried out analogously to example 1. The test results of corrosion inhibitors, scaling and biodeterioration are presented in the table.

 As can be seen from the table, preparations of polyhexamethylene guanidine hydroxyethylidene bisphosphonates at concentrations of 20-100 mg / l are effective for inhibiting corrosion, scaling and biofouling.

Claims (1)

 The use of hydroxyethylidene bisphosphonates of polyhexamethylene guanidines as inhibitors of corrosion, scale and metal fouling.

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