ASSESSMENT OF THE INHIBITORY PROPERTIES OF A CORROSION INHIBITOR IK-1 IN AQUATE AND SALT ENVIRONMENTS

ABSTRACT

The environmental safety of using the developed inhibitors in IK-1 systems in aqueous and saline water supply environments and circulating waters, as well as in the oil and gas chemical industry, has been demonstrated, and their effectiveness has been determined. It has been shown that the most important part of the protective properties of compounds containing phosphorus and nitrogen are amino acids or long-chain hydrocarbon radicals located on the donor nitrogen atoms of phosphorylphosphorus.

АННОТАЦИЯ

Показана экологическая безопасность применения разработанных ингибиторов в системах ИК-1 в водных и солевых средах водоснабжения и циркулирующих водах, а также в нефте- и газо-химической промышленности и определены их эффективность. Показано, что важнейшую часть защитных свойств соединений, содержащих фосфор и азот, составляют аминокислоты или длинноцепочечные углеводородные радикалы, расположенные на донорных атомах азота фосфорилфосфора.

Keywords: corrosion inhibitors, diethanolamine, oleic acid, zinc adduct, metal corrosion, phosphoric acid, nitrogen-phosphorus inhibitors, amine groups.

Ключевые слова: ингибиторы коррозии, диэтаноламин, олеиновая кислота, аддукт цинка, коррозия металла, фосфорная кислота, азот-фосфорсодержащие ингибиторы, аминные группы.

Introduction. The inhibitory compounds used are mainly based on chemically pure reagents, which naturally affects the cost of production. The literature describes metal corrosion inhibitors in water, aqueous solutions of acids, alkalis, salts, as well as corrosion inhibitors in atmospheric conditions and in non-aqueous liquid media. In addition to practical recommendations and the results of numerous experimental studies, many literatures provide a review of theoretical ideas about the mechanism of action of inhibitors, as well as their classifications[1].

Considering the above, the purpose of this work is to obtain new highly effective high-molecular corrosion inhibitors containing phosphoric acid and amine groups and to study the process of corrosion inhibition.  In general, given the current full import of expensive corrosion inhibitors, it seems advisable to study the creation and use of new oligomeric corrosion inhibitors [2].

Phosphorus- and nitrogen-containing compounds, based on their protective properties, have shown that the most essential fragment of molecules that determines their protective properties is a long-chain hydrocarbon radical located at the donor nitrogen atoms of the amino group or phosphorus of the phosphoryl group [3].

Experimental part. In this work, oligomeric corrosion inhibitors synthesized based on diethanolamine, oleic acid and zinc adduct IK-1 were studied.

The reaction was carried out in a 500 ml flask equipped with a reflux condenser for 9 hours at a temperature of 180-200^oC. The corrosion inhibitor is used in tower cooling systems. One of the most effective corrosion inhibitors in aqueous systems is the IR-1 inhibitor.

The degree of protection of corrosion inhibitors was calculated using the formula

Vko - corrosion rate of samples in an uninhibited environment, g/m² h

Vki - corrosion rate of samples in an inhibited environment, g/m² h

IK-1 and Puro-tech Corrosion rate indicator Kmass, determined by the formula

g₀ – mass of the sample in the initial state

g₁ – mass of the sample after the reaction

S – surface under study

T – test time

IK-1

Puro-tech

Conversion of the mass index of corrosion to the depth index is carried out according to the formula

where P is the index of deep corrosion

Kmass is a mass indicator of corrosion rate.

- metal density 

The traditional way of graphically processing polymerization curves to determine the corrosion rate is to extrapolate in semilogarithmic coordinates the rectilinear sections of the cathode and anodic branches until their mutual intersection. However, despite the obvious simplicity of the method, its practical use is often associated with a number of complications. The construction of tangents itself is quite subjective, and for a more reliable extrapolation, an additional accurate determination of the corrosion potential is necessary [4,5].

In the IR spectrum of sample IR-1 (NH2), the bands due to the asymmetric and symmetric stretching vibrations of the group are attributed to the stretching vibration of 3280 cm-1, and the bands at 2939 and 2852 cm-1 in the spectrum are attributed to the asymmetric and symmetric vibrations of the methylene group, respectively. 2361 cm-1 (R-H) stretching bond, 1456 cm-1 (-SN2) asymmetric bending bond, 1402 cm-1 symmetric methyl stretching bond (-SN3), 1365 cm-1 -S-N-asymmetric bond, 1053 cm1 band caused by asymmetric and symmetric stretching vibrations of -1 (-P-O-C-) groups. Low-intensity lines in the spectral regions of 1305 and 722 cm-1 are associated with rotational and pendulum vibrations of the methylene group.

Figure 1. IK spectrum of sample IK-1

Results and its discussion. An analysis of the studies has shown that changes in the corrosion rate and the effectiveness of the inhibitor depend on the concentration of the inhibitor. Table 1 shows data on the effectiveness of the corrosion inhibitor in aqueous environments.

Experimental data on studying the corrosion rate of steel plates in aqueous dispersions of IK-1, both with and without additives, showed that when the concentration changes, the stationary potential of the electrode shifts to the positive region, due to the formation of a barrier type of corrosion protection. This effect increases significantly with increasing concentration of the oligomeric inhibitor in the aqueous dispersion.

Along with this, it should be noted that the nature of the adsorption of the inhibitor on the surface of the electrode, the effectiveness of its action, as well as whether the inhibitors belong to the cathodic and anodic types depend not only on its nature, but also to a large extent on the potential of the medium. Judging by the steady-state potential, with the addition of IK-1, the degree of protection increases significantly. Moreover, more effective protection against corrosion occurs in the presence of a 0.2% solution of IK-1, the protective coefficient of which passes through a maximum.

Table 1.

Protective properties of the corrosion inhibitor oligomer in aqueous and saline environments at 40°C 250 hours

The mechanism of action of this oligomeric corrosion inhibitor is determined mainly by the transition of the surface-protected metal to a stable surface film state with the participation of particles of fine additives. However, the action of inhibitors in this case is more complex than in film formation, and is also associated with the nature of adsorption of surfactant ions [6]. For example, when the surface charge of the electron is positive relative to the solution, an oligomeric inhibitor, which is anions, will be adsorbed on it, while the inhibitor surface is negatively charged, which are undissociated molecules. Thus, when moving to another process condition, the structure of the coatings or the stationary potential of the metal changes. By changing the composition of the solution or applying external polarization, the nature of adsorption and, consequently, the nature and effectiveness of inhibitors based on phosphorus- and nitrogen-containing oligomers can change. In general, the oligomeric corrosion inhibitors we synthesized have a fairly high anti-corrosion efficiency.

Conclusion. Inhibitors with substituents at the phosphoryl group are more effective in protecting against corrosion. The protective effect of nitrogen-phosphorus-containing inhibitors is due to the formation of densely packed films on the steel surface.

The protective effect of multicomponent polymer-type inhibitors based on production waste and local raw materials has been achieved up to 5 percent higher than that of imported inhibitors [7].

The environmental safety of using the developed inhibitors in water supply and recycling water supply systems, as well as in the petrochemical industry, has been demonstrated; their effectiveness has been determined to be 95,15%.

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