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CHEMICAL PROBLEMS 2021 no. 1 (19) ISSN 2221-8688
37
UOT 620.197.3
POLARIZATION STUDIES OF STEEL IN THE PRESENCE OF SYNERGETIC MIXTURES BASED ON INORGANIC OXIDIZERS AND MONOETHANOLAMINE IN
SODIUM CHLORIDE SOLUTIONS
S.Ch. Verdiev \ S.Z. Dzhafarova 2,3
1Acad. M. Nagiyev Institute of Catalysis and Inorganic Chemistry of the National Academy of Sciences of Azerbaijan H. Javid ave., 113, AZH43, Baku, Azerbaijan Republic
2Azerbaijan State University of Economics (UNEC) Istiglaliyyat ave., 6, AZ1001, Baku, Azerbaijan Republic 3Acad. G. Abdullayev Institute ofPhysics of the National Academy of Sciences of Azerbaijan H. Javid ave., 135, AZ1143, Baku, Azerbaijan Republic e-mail: exiton_1992@,mail. ru
Received 09.03.2021 Accepted 13.04.2021
Abstract: Polarization studies have shown that the effect of inhibitors containing inorganic oxidants and monoethanolamine reduces the corrosion rate of steel in 3% NaCl. This decrease unambiguously indicates a simultaneous slowing down of the cathodic reduction of molecular oxygen and the anodic reaction of metal ionization. Based on the studies carried out, it was concluded that the developed mixtures function as mixed -type inhibitors.
Keywords: polarization, inhibitor, cathodic and anodic processes, ionization, synergetic effect. DOI: 10.32737/2221-8688-2021-1-37-40
Introduction
According to previously obtained data [1-5], it showed that the combined introduction of inorganic oxidizing agents and amines at the certain ratios into a corrosive medium leads to a noticeable decrease in the corrosion rate of carbon steel. In this regard, it is of scientific interest to study corrosion-electrochemical properties of St.3 in these mixtures and find out
reasons of braking effect of the used inhibitors.
Previously, we obtained data on the effect of the concentration of inhibitors on electrode potentials under open circuit conditions, since these changes can be used to indirectly judge about possible effect of synergistic mixtures on the course of electrode reactions occurring on the steel surface.
Experimental part
Electrochemical measurements were carried out on a Pi-50-1 potentiostat with a separated anode and cathode space. As an electrode, a rotating disk electrode (970 rpm) was taken from steel gradest 3 with a working surface of 1 cm. Potentials were measured
relative to the silver chloride electrode and recalculated to the normal hydrogen scale. The auxiliary electrode was platinum. Polarization curves were recorded in the potentiodynamic regime with a potential sweep rate of 12 mV per minute.
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CHEMICAL PROBLEMS 2021 no. 1 (19)
Results and discussion
The removal of polarization curves in the potentiodynamic regime for the tested metal in a given corrosive sphere without additives and in the presence of inhibitors allows us to find out
which of the processes (anode or cathode) is mainly braked by the introduction of inhibitors, components and their mixtures.
i, m. 4 cm
Fig. l. Cathode, anode polarization curves of St. 3 in a 3% NaCl solution with the addition of an inhibitor, mg/1: 1-1 '- without inhibitor; 2-2'-NaNO2-100; 3-3'-MEA - 100; 4-4'- NaNO2 -100 +
MEA - 100
In Fig. 1 polarization curves taken in a 3% NaCl solution and in the presence of monoethanolamine (MEA) are presented, NaNO2 individually and in their mixture. As can be seen from Fig. 1, with the addition of NaNO2 (100 mg/1) in the background solution (3% solution of NaCl), the electrode potential is shifted to a positive direction at 80 mV. At the same time, both cathodic and anodic processes are simultaneously braked, and the inhibition of the latter is stronger. With the addition of monoethanolamine (100mg/g) to the background solution, the cathodic process is mainly inhibited. The addition of both NaNO2 and monoethanolamine (100mg/g) to the solution simultaneously leads to stronger suppression of both cathodic and anodic processes (Fig. 1. curves 4-4'.)
As follows from Fig.1, both individually and jointly, NaNO2 and MEA are able to change the kinetics of electrochemical processes on
steel and lead to a noticeable decrease in the corrosion rate. The greatest effect is observed in the mixture of these inhibitors. In this work, along with the above mentioned inhibitor, we studied other mixtures of inhibitors as well, in particular, mixtures of potassium chromate and MEA. Polarization measurements showed that the combined presence of two components in the mixture (K2CrO4+MEA) leads to a noticeable braking of cathodic and anodic processes. Moreover, the inhibition of the anode process in this case is greater than in the presence of sodium nitrate (Fig. 2). A study into kinetics of the anodic ionization reaction of steel in the presence of a mixture of MEA with sodium molybdate revealed that although monoethanolamine and sodium molybdate contribute to some anodic polarization of the electrode, their mixture with a synergistic property, has the greatest influence on this process.
In our opinion, the mechanism of the protective effect of MRA mixture and NaNO2 is that a chemisorbed layer of iron hydroxide which includes monoethanolamine is formed on the outer protective layer of iron oxide, and in the case of chromate with MEA, a complicated
complex of chromium with iron of the chelated type is formed on the steel surface.
Thus, there is a definite correlation of the influence of studied inhibitors on the corrosion rate and the anodic reaction of steel ionization.
/, m A/cm'
Fig. 2. Cathode and anode polarization curves of St. 3 in a 3% NaCl solution with the addition of an inhibitor, mg/1: 1-1'- without inhibitor; 2-2'- K2Cr04 10; 3-3' - H2N - CH2 - CH2 - OH - 90; 44'- K2Cr04-l 0 + H2N - CH2 - CH2- OH- 90
Conclusion
Electrochemical studies show that in neutral electrolytes a synergistic effect of inhibiting the corrosion process is observed, with the combined presence of these oxidizing
agents and MEA in a corrosive environment. These mixtures exert a braking effect both on cathodic and anodic processes.
References
1. Verdiev S.Ch., Kazakhsky L.P., Bayramov A.Kh., Kyazimov A.M. On the nature of the synergism of oxidative inhibitors and monoethanolamine on the surface of steel in a chloridesolution. Metal Protection. 1987. vol. XXIII, no. 2, pp. 264-269. (In Russian).
2. Verdiev Ch., Tagirli H.M., Agalarova T.A., Huseynova A.S., Velieva S.M., Jafarova S.Z., Mamedova S.R. Inhibition of contact corrosion of metals in fresh water with mixtures of oxidizing agents and amines. Chemical Problems. 2019, vol. 3, no.17, pp.
465-469.
3. Rakova T.M., Kozlov A.A., Nefedov N.I., Lapatov A.B. Study of the effect of organic and inorganic corrosior inhibitors on corrosion cracking of high-strength steels. Proceedings of the All-Russian Scientific Research Institute of Aviation Materials (VNAM). 2017. vol. 6, no. 54, pp. 102-110.
4. Grigorieva I.O., Dressvyanikov A.F. The effect of the composition and concentration of nitrate-containing electrolytes on the anodic dissolution and the corrosion behavior
of aluminum. Bulletin of Kazan Technological University. 2012. no.1, pp. 6972.
5. Verdiev S.Ch., Tagirli H.M., Agalarova T.A., Huseynova A.S., Velieva S.M. Investigation
of the effect of the combined inhibitory effect of inorganic oxidants and monoethanolamine on steel corrosion in a two-phase electrolyte-hydrocarbon medium. Journal «Caspian Corrosion Control». 2019. no.1, pp. 6-10.
QEYRi-UZVi OKSiDLdÇDiRiCiLdRiN VO MONOETANOLAMiN OSASINDA HAZIRLANMIÇ iNHiBiTOR QARI$IGININ OLDUGUNATRIUMXLORiD MOHLULLARINDA POLYARLAÇMANIN TODQiQi
S.C. Verdiyev1, S.Z. Cafarova2'3
1AMEA -nin Kataliz va Qeyri-uzvi Kimya institutu, AZ1143, Baki, H.Cavidpr.113 2 Azarbaycan Dovlat iqtisad Universiteti, AZ1001, Baki, Istiqlaliyyatpr.,6 3AMEA -nin Fizika institutu, AZ1143, Baki, H.Cavidpr.135 e-mail: exiton_1992@,mail. ru
Polyarla§ma tadqiqatlari naticasinda malum olmuçdur ki, tarkibinda qeyri -uzvi oksidlaçdiricilar va monoetanolaminin oldugu inhibitorlar poladin korroziya suratini azaldir ki, bu da birqiymatli molekulyar oksigenin reduksiyasi va anod reaksiyasi olan metalin ionlaçma proseslarinin langimasina dalalat edir. Har iki prosesin langimasi hazirlanmiç inhibitor sistemlarin qariçiq tipli olduqlarini tasdiq edir. Açar sôzlar: polyarlaçma, inhibitor, katod va anodproseslari, ionlaçma, sinergetik effekt
ПОЛЯРИЗАЦИОННЫЕ ИССЛЕДОВАНИЯ СТАЛИ В ПРИСУТСТВИИ СИНЕРГЕТИЧЕСКИХ СМЕСЕЙ НА ОСНОВЕ НЕОРГАНИЧЕСКИХ ОКИСЛИТЕЛЕЙ И МОНОЭТАНОЛАМИНА В РАСТВОРАХ ХЛОРИСТОГО НАТРИЯ
С.Ч. Вердиев1, С.З. Джафарова2'3
1 Институт Катализа и Неорганической Химии АН Азербайджана
AZ1143, Баку, пр. Г. Джавида,113 2Азербайджанский Государственный Экономический Университет AZ1001, Баку, пр. Истиглалият, 6 3 Институт Физики Национальной АН Азербайджана AZ1143, Баку, пр. Г. Джавида,135 e-mail: exiton_1992@,mail. ru
Поляризационные исследования показали, что влияние ингибиторов, содержащие неорганические окислители и моноэтаноламин, уменьшают скорость коррозии стали в 3%-м растворе NaCl. Это уменьшение однозначно свидетельствует об одновременном замедлении катодного процесса восстановления молекулярного кислорода и анодной реакции ионизации металла. На основе проведенных исследований сделано заключение о том, что разработанные смеси функционируют как ингибиторы смешанного типа.
Ключевые слова: поляризация, ингибитор, катодные и анодные процессы, ионизация, синергетический эффект.
