Assessment of the protective effectiveness of a volatile inhibitor in atmospheric corrosion of steel under conditions of increased concentrations of carbon dioxide, ammonia and hydrogen sulfide by electrochemical methods

• V.I. Vigdorovich¹, L.E. Tsygankova², N.V. Shel³, L.G. Knyazeva¹, A.V. Dorokhov¹ and A.A. Uryadnikov²

¹ All-Russian Scientific Research Institute of Use of Machinery and Oil Products, Novo-Rubezhnyi per., 28, Tambov, 392022, Russian Federation
² Derzhavin State University, ul. Internatsyonalnaya, 33, Tambov, 392000, Russian Federation
³ Tambov State Technical University, ul. Sovetskaya, 106, Tambov, 392000, Russian Federation

Abstract: The effect of the combined presence of atmospheric corrosion stimulants NH₃ and CO₂ was modeled by introducing (NH₄)₂CO₃ salt into the solution. And the presence of NH₃ and H₂S was modeled by introducing the corresponding amounts of NH₄OH and H₂S into the solution. The presence of these corrosion stimulants in the air is characteristic for livestock buildings. The influence of the concentration of (NH₄)₂CO₃ and (NH₄)₂S salts (10–500 mg/L) and the IFKHAN-114 volatile inhibitor (100 mg/L) during the corrosion of St3 steel in a 0.1 M NaCl solution was studied using methods of potentiodynamic polarization and spectroscopy of electrochemical impedance. Potentiodynamic measurements at a potential sweep rate of 0.66 mV/s were carried out in a three-electrode electrochemical cell made of Pyrex glass with a platinum auxiliary electrode and silver–silver chloride reference electrode using an IPC-Pro MF potentiostat. It was shown that in the absence of IFKHAN-114, the products of the hydrolysis of both salts as a result of their almost complete conversion to ammonium hydroxide and the corresponding weak acids cause intensive inhibition of corrosion of St3 carbon steel in 0.1 M NaCl solution. The protective effect reaches 90–96%. Introduction of IFKHAN-114 (100 mg/L) at low concentrations of (NH4₄)₂CO₃ (10 mg/L) has a stimulating effect on St3 steel, but starting with 20 mg/L of the salt this effect is replaced by an inhibitory one. Its value increases with increasing salt concentration, reaching 67% with a formal content of 100 mg/L ammonium carbonate in the solution. In the presence of ammonium sulfide, the protective effect is maximum at a low salt content (10 mg/L) and significantly decreases with increasing salt concentration, more precisely the products of its complete hydrolysis. The impedance measurements confirm the results obtained by the method of potentiodynamic polarization.

Keywords: steel, volatile inhibitor, corrosion, atmosphere, ammonia, hydrogen sulfide, carbon dioxide, polarization, impedance

Int. J. Corros. Scale Inhib., 2020, 9, no. 1, 34-43 PDF (510 K)
doi: 10.17675/2305-6894-2020-9-1-2

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