RU2776118C1 - Inhibitor of hydrochloric acid corrosion of steel - Google Patents

Abstract

FIELD: corrosion protection.

SUBSTANCE: invention relates to the field of protection of metals from corrosion and can be used to protect oilfield equipment and pipelines operated in aggressive environments. The use of 5-substituted 2-amino-1,3,4-thiadiazole of general formula

as an inhibitor of hydrochloric acid corrosion of steel St3 in the concentration range of 50-200 mg/l in 1 M HCl solution is proposed.

EFFECT: new compounds of thiadiazoles have been found, which increase the resistance of steel to corrosion during hydrochloric acid treatment of wells.

1 cl, 2 tbl, 4 ex

Description

The invention relates to the use of 5-substituted 2-amino-1,3,4-thiadiazoles of the general formula

as inhibitors of acid corrosion of carbon steel and can be used to protect metals in the oil industry to prevent corrosion of equipment and pipelines operating in aggressive environments. One of the most effective methods of combating corrosion damage of process equipment is inhibitor protection. The effectiveness of this method is confirmed by a number of advantages, including the possibility of intervening in the corrosion process at various stages of the course. In addition, relatively small capital costs can significantly slow down the processes of corrosion damage and degradation of the mechanical properties of metals and alloys, thereby slowing down the destruction of equipment.

The current world trend is the development of environmentally friendly corrosion inhibitors based on heterocyclic compounds (Ambrish Singh, K.R. Ansari, Dheeraj Singh Chauhan, M.A. Quraishi, H. Lgaz, III-Min Chung, Comprehensive investigation of steel corrosion inhibition at macro/micro level by ecofriendly green corrosion inhibitor in 15% HCl medium, Journal of Colloid and Interface Science, Volume 560, 2020, pp 225-236), as they are more economical and promising compared to nanomolecular ZnO-based protective compounds (Moses M. Solomon, Husnu Gerengi, Tugce Kaya, Savior A. Umoren, Performance Evaluation of a Chitosan/Silver Nanoparticles Composite on St37 Steel Corrosion in a 15% HCl Solution, ACS Sustainable Chem Eng 2017, 5.1 pp. 809-820). These compositions based on nanosized emulsions are successfully used in atmospheric conditions, but do not provide the necessary protection for liquid aggressive media (Patent 2460748).

The aim of the invention is to search for new compounds of thiadiazoles, which increase the resistance of steel to corrosion during hydrochloric acid treatment of wells.

The goal is achieved by the fact that 5-substituted 2-amino-1,3,4-thiadiazoles exhibit a high protective effect of St3 steel (GOST 380-2005) in the concentration range of 50-200 mg/l in a 1 M HCl solution.

Example 1

2-amino-5-sitryl-1,3,4-thiadiazole

Mix 9.1 g of thiosemicarbazide and 14.8 g of cinnamic acid and grind them in a porcelain mortar until smooth. The resulting mixture is transferred to a 250 ml round-bottom flask and, with stirring and cooling to 0° C., 27.4 ml of phosphorus oxychloride (POCl ₃ ) are added at a rate of 1 ml per minute. After the addition of POCl ₃ the resulting mixture is heated with stirring to 70°C and maintained at this temperature for 4 hours. 50 ml of water, 40% sodium hydroxide solution are successively added dropwise to the resulting solution to pH 8-9. The precipitate formed is filtered off and washed with water until the wash water medium is neutral. Light yellow solid compound, 46% yield. ¹ H NMR spectrum (400 MHz, DMSO d ₆ ) δ 7.62, 7.63 (d, J=7.3 Hz, 1H, Ph), 7.29-7.44 (m, 7H, Ph, NH ₂ , CH=), 7.04, 7.08 ( e, J=16.3 Hz, 1H, CH=). ¹³ C NMR (400 MHz, DMSO d ₆ ) δ 167.6, 156.8, 135.9, 134.2, 128.7, 126.9, 119.67.

Example 2

2-amino-5-heptyl-1,3,4-thiadiazole

In a 250 ml round bottom flask, 9.1 g of thiosemicarbazide and 14.4 g of octanoic acid are mixed until homogeneous. With stirring and cooling to 0°C, 27.4 ml of phosphorus oxychloride (POCl ₃ ) are added at a rate of 1 ml per minute. After the addition of POX, the resulting mixture is heated with stirring to 70°C and maintained at this temperature for 4 hours. 50 ml of water, 40% sodium hydroxide solution are successively added dropwise to the resulting solution to pH 8-9. The precipitate formed is filtered off and washed with water until the wash water medium is neutral. White solid compound, 64% yield. ¹ H NMR spectrum (400 MHz, CDCl ₃ ) δ 5.96 (s, 2H, NH ₂ ), 2.86-2.90 (t, J=7.4 Hz, 2H, CH ₂ ), 1.68-1.74 (m, 2H, CH ₂ - CH ₂ -). 1.29-1.44 (m, 8H), 0.87-0.90 (t, J=6.5 Hz, 2H, -CH ₃ ). ¹³ C NMR (400 MHz, CDCl ₃ ) δ 168.2, 161.6, 31.6, 30.34, 29.4, 28.9,28.8,22.5, 13.9.

Example 3

Corrosion tests are carried out under laboratory conditions by the gravimetric method (GOST 9.506-87) in a 1 M solution of hydrochloric acid in water.

The corrosion rate (K), the degree of inhibition (γ) and the inhibitory effect (Z _gr ) were evaluated according to the following formulas:

where m ₀ is the mass of the original sample, g; m is the mass of the sample after corrosion testing and removal of corrosion products, g; S is the surface area of the sample, m ² ; τ - test time, h; where K ₀ and K are the corrosion rates of steel, respectively, in pure solution and with the addition of an inhibitor, g / m ^{2 *} hour.

Example 4 Determination of the protective characteristics of 4,5-diphenyl-4H-1,2,4-trialo-3-thiol was carried out by the electrochemical method temperature, the cell was connected to a LOIP LT 100 thermostat with external circulation.

The protective effect (Z _{el / x} ) was calculated from electrochemical data:

и i_кор - плотности тока коррозии стали соответственно в чистом растворе и с добавкой ингибитора, А/м² where

and i _cor - steel corrosion current densities, respectively, in pure solution and with the addition of an inhibitor, A / m ²

Claims (3)

The use of 5-substituted 2-amino-1,3,4-thiadiazole of the general formula

as an inhibitor of hydrochloric acid corrosion of St3 steel in the concentration range of 50-200 mg/l in 1 M HCl solution.