SYNTHESIS OF NEW TYPES OF CORROSION INHIBITORS CONTAINING COMPOUNDS OF PHOSPHORUS, NITROGEN AND SULFUR, AND TESTING IN AN AGGRESSIVE ENVIRONMENT

ABSTRACT

Currently, work is underway around the world to develop new multifunctional compositions that inhibit corrosion, aimed at obtaining environmentally friendly corrosion inhibitors from secondary industrial products and the efficiency of using phosphorus-, sulfur-, and nitrogen-containing corrosion inhibitors. In this aspect, heterocyclic compounds containing functional groups of phosphorus, sulfur, oxygen or nitrogen are of certain scientific and practical interest. In this case, phosphorus, nitrogen, oxygen or sulfur-containing compositions can be used to obtain highly effective corrosion inhibitors. Therefore, the study of the synthesis processes of these compositions, their physicochemical characteristics, as well as possible areas of application and the development of technology for their production are important.

АННОТАЦИЯ

В настоящее время в мире ведутся работы по разработке новых полифункциональных композиций, ингибирующих коррозию, направленных на получение экологически чистых ингибиторов коррозии из вторичных промышленных продуктов и эффективности использования фосфор-, сера-, азот содержащих ингибиторов коррозии. В этом аспекте определенный научный и практический интерес представляют гетероциклические соединения, содержащие функциональные группы фосфора, серы, кислорода или азота. При этом фосфор, азот, кислород или серосодержащие композиции могут быть использованы с целью получения высокоэффективных ингибиторов коррозии. Поэтому изучение процессов синтеза этих композиций, их физико-химические характеристики, а также возможные области применения и разработка технологии их получения являются важными.

Keywords: corrosion inhibitors, metal corrosion, phosphorus, sulfur, crotonaldehydes, phosphate acids, adduct, polyfunctional inhibitors.

Ключевые слова: ингибиторы коррозии, коррозия металла, фосфор, сера, кротоновые альдегиды, фосфатные кислоты, аддукт, полифункциональные ингибиторы.

Introduction. Today it is important to create environmentally friendly, non-toxic, biodegradable inhibitors that will be highly effective in a very aggressive environment, even in low concentrations.

In a world with intensively developing industry in various sectors of the economy, preventing metal corrosion and creating inhibitory systems is of great theoretical and practical importance. In countries with developed chemical and petrochemical industries, metal corrosion causes great economic damage, so the creation and practical use of highly effective corrosion inhibitors is even more important.

Currently, work is underway around the world to develop new multifunctional inhibitors of chemical, electrochemical, microbiological corrosion and salinity. In this regard, compounds of nitrogen, sulfur and phosphorus, crotonaldehydes, ammonia, phosphate acids and organophosphorus compounds, their compositions and metal ions can be used to obtain a number of multifunctional inhibitors. Based on the above, it is necessary to develop a technology for the synthesis of oligomeric corrosion inhibitors [1].

Composite materials with high inhibitory efficiency as a result of the use of phosphorus, nitrogen and sulfur-containing organic compounds have been developed here. The optimal conditions for the synthesis of phosphorus, nitrogen and sulfur-containing inhibitory compositions and the structure of these compositions were also determined. The physicochemical properties of the obtained phosphorus, nitrogen and sulfur-containing composite corrosion inhibitors were determined. The mechanisms of chemical interaction between phosphorus, nitrogen and sulfur-containing heterocyclic compounds with the adduct and the composition of the resulting inhibitory composition have been established. The dependence of the physicochemical and inhibitory properties of the resulting compositions on the ratio of components in the adduct has been proven. A technology has been developed for the production of new phosphorus, nitrogen and sulfur-containing compositions of corrosion inhibitors based on local raw materials [2].

Experimental part. This method of estimating corrosion rate is based on measuring the weight loss of metal samples over a certain period of time in an aggressive environment. The studies were carried out on a steel-iron electrode ST-20, made of tubular steel with dimensions of 30x15x12 mm.

The gravimetric method is one of the effective methods for determining the corrosion rate of metals in laboratory conditions. In this case, it is determined by the difference in the mass loss of the metal under study when an inhibitor is added to the solution and when it is absent. We conducted practical experiments at different temperatures and different concentrations to determine the corrosion rate of steel. The corrosion rate of the steel sample taken for the experiment was determined over a period of 24 to 240 hours (Table 1).

Here: (K) corrosion rate,

(X) weight loss,

m₁ is the initial mass of the metal sample,

m₂ – mass of the corroded metal sample,

S is the surface area of ​​the sample taken for the practical experiment,

t₁—exposure time.

          Results and its discussion. This method is one of the simplest methods for determining the degree of corrosion of metals, does not require complex and expensive equipment and can provide a large amount of data [3].

Table 1.

Gravimetric determination of the inhibitor IK-1 at various concentrations and temperatures for 240 hours in an environment of 0.5 M H₂SO₄.

In 0.5 M sulfuric acid, the maximum inhibition efficiency of the IK-1 inhibitor is 91.86% at a temperature of 40°C, however, increasing the temperature to 50°C reduces the degree of protection of this corrosion inhibitor.

Analysis of adsorption isotherms and thermodynamics of adsorption of inhibitors. Frumkin, Temkin and Langmuir isotherms of the mechanism of adsorption of the inhibitor IK-1 on the steel surface at various temperatures and concentrations were obtained [4].

Figure. Temkin isotherm plot for IK-1 inhibitor.

The closeness of the correlation coefficient of the experimental results obtained from the linear form of the Langmuir isotherm showed that the process obeys the theory of monomolecular adsorption. The theory of monomolecular adsorption, based on the Langmuir isotherm, provides additional information about the mechanism of interaction between the steel surface and the inhibitor. As a result of the experiment, it was found that the value of the Gibbs energy decreases with increasing temperature, which indicates that the process occurs spontaneously [5;6].

Conclusions. The service life of metal structures under natural environmental conditions is often relatively short. When operating systems that involve the repeated use of limited volumes of water and the use of waste water in cooling circuits, problems arise associated with the deposition of poorly soluble compounds on the surface of the equipment, as well as its damage due to corrosion processes [7]. The developed IK-1 corrosion inhibitors have successfully passed laboratory tests. Calculations have shown that the economic effect of using the IK-1 corrosion inhibitor composition increases with increasing service life of construction, transport and electrical materials, as well as with the replacement of imported materials.

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