ISSN 2305-6894

The use of chiral anionic Co(III) complexes as inhibitors of corrosion and hydrogen absorption in water–salt media containing biogenic hydrogen sulfide

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1 Immanuel Kant Baltic Federal University, 236041 Kaliningrad, Russian Federation
2 Kaliningrad Regional Institute of the educational development, 236016 Kaliningrad, Russian Federation
3 Southern Federal University, ul. Zorge 7, Rostov-on-Don, 344090 Russian Federation
4 All-Russian scientific research institute for the use of machinery and oil products in agriculture, 392022 Tambov, Russian Federation
5 Sarasas International School, Bangkok, Thailand

Abstract: In this report we present the results of experimental and theoretical studies of organic compounds (OС) – chiral anionic complexes of Co(III) – as inhibitors of corrosion and hydrogen absorption of mild steel. We also estimated the bactericidal effect of organic compounds on sulfate-reducing bacteria (SRB). It was of interest to evaluate the corrosiveness of SRB in the presence of the organic compounds studied in the corrosive environment. The water–salt medium Postgate B that is favorable for the development of SRB was used as an corrosive medium. SRB that directly participate in the electrochemical process are the main causative agents of steel corrosion. Experimental data on the efficiency of the compounds studied as corrosion inhibitors and as inhibitors of hydrogen absorption by mild steel in Postgate B water–salt medium in the presence of sulfate-reducing bacteria are compared with theoretical results on the calculation of some quantum-chemical parameters. To interpret the experimental results obtained, we performed ab initio (MP/2), MNDO, PM/3, and AM/1 quantum chemical calculations using the Gaussian 03 software package. The values of the following quantum-chemical descriptors for the studied compounds were determined: the energies of the boundary orbitals (HOMO and LUMO) [13] and the moduli of the dipole moments for the isolated molecules of each inhibitor. The results obtained showed that OC4, OC5, OC8, and OC9 are the most efficient inhibitors of corrosion and hydrogenation with a bactericidal effect on SRB. The protective effect in gravimetric tests for these compounds is 90-93%. They reduce the hydrogen content at a depth of 30 microns 1.8–2.8 fold. The number of SRB cells is reduced 2–3 fold, depending on the exposure time. The descriptors obtained by quantum-chemical calculations confirm the experimental data.

Keywords: organic inhibitors of corrosion and hydrogen absorption, mild steel, sulfate-reducing bacteria, biocide, quantum-chemical calculations, dipole moment

Int. J. Corros. Scale Inhib., , 9, no. 4, 1277-1286 PDF (507 K)
doi: 10.17675/2305-6894-2020-9-4-6

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