Naberezhnye Chelny Institute (branch) of Kazan Federal University, Naberezhnye Chelny, Russia:

D. D. Fazullin, Cand. Eng., Associate Professor, e-mail: denr3@yandex.ru
G. V. Mavrin, Cand. Chem., Associate Professor
L. I. Fazullina, Leading Engineer

Kazan National Research Technological University, Kazan, Russia:
I. G. Shaikhiev, Dr. Eng., Professor;

Kazan Zavoisky Physical-Technical Institute, FRC Kazan Scientific Center of the Russian Academy of Sciences, Kazan, Russia¹ ; Kazan Federal University, Kazan, Russia²:
N. M. Lyadov, Scientific Researcher^{1, 2}

In this work, steel corrosion inhibitors from vegetable raw materials have been obtained to protect oilfield equipment from the corrosive action of formation waters. Extracts from the bark of "Norway spruce" and "Scots pine" were used as an inhibitor of steel corrosion. The main component of spruce and pine bark extracts with an anti-corrosion effect is tannins - a group of phenolic compounds of plant origin that have tanning properties and are capable of forming compounds with iron that are slightly soluble in water - iron tannates. The content of tannins in the extract from the bark of Norway spruce was 13.4%, in the extract from the bark of pine - 3.3 %. Corrosion tests were carried out in accordance with GOST 9.506-87 and GOST 9.502-82. The degree of protection of steel grade "Steel 20" with the addition of the spruce bark extract was 88.9 %, with the addition of pine bark extract - 74.9 %, at a dosage of 50 g/dm³. Commercial corrosion inhibitors of steel grades SNPKh-1004 and TNKhS-7 at a dosage of 1g/dm³ showed the degree of steel protection up to 92 and 90.3 %, respectively. Corrosion of steel in the formation water of oil of the Devonian sediment develops 1.5 times more intensively than in the model formation water. The best result in terms of the degree of steel protection with the addition of spruce bark extract and pine bark extract with a concentration of 50 g/dm³ was 80.0 % and 41.8 %, respectively. Thus, the corrosion resistance of the metal in accordance with GOST 9.502-82 as a result of the use of spruce bark extract as a corrosion inhibitor in the model formation water corresponds to the "stable" level, in the formation water of oil of the Devonian sediment it corresponds to the "reduced" level.
Electron-microscopic measurements were carried out within the framework of the state task of the Federal Research Center of KazSC RAS No. AAAA-A18-118041760011-2.

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