Protection of low-carbon steel in acetic acid solutions by mixtures of a substituted triazole with sulfur-containing compounds

• Ya.G. Avdeev and T.E. Andreeva

Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, 31-4, Leninsky prospect, 119071 Moscow, Russia

Abstract: The corrosion of low-carbon steel 20 in acetic acid solutions (2–6 M) over the temperature range of t=20–60℃ in the presence of various additives and mixtures of additives was studied. The additives included IFKhAN-92 inhibitor (3-substituted-1,2,4-triazole), Catamine AB (aqueous solution of a mixture of alkylbenzyldimethylammonium chlorides [H₃C–(CH₂)_n–N⁺(CH₃)₂CH₂C₆H₅]Cl^–, where n=9–17), hexamethylenetetramine, potassium bromide, potassium iodide, potassium thiocyanate, sodium diethyldithiocarbamate (DEDTC), 2-mercaptobenzothiazole, 2,2′-dibenzothiazyl disulfide, thiourea, phenylthiourea, and diphenylthiourea. Efficient protection of steel in acetic acid solutions is provided by compositions containing 5 mM IFKhAN-92+0.5 mM additive (additive = DEDTC, 2-mercaptobenzothiazole, 2,2′-dibenzothiazyl disulfide, thiourea, phenylthiourea, diphenylthiourea, or potassium thiocyanate), which inhibit the metal corrosion by a factor of at least 25. An efficient mixture for the protection of low-carbon steel in hot acetic acid solutions was developed on the basis on the IFKhAN-92 inhibitor and DEDTC (molar ratio of the components 10:1). The proposed composition protects steel in acetic acid solutions over a wide range of concentrations (2–6 M) and temperatures (20–100℃). According to the results of two-hour corrosion tests, the maximum corrosion rate of steel in these media does not exceed 48 g/(m²∙h); in the presence of 5 mM IFKhAN-92+0.5 mM DEDTC, the rate is as small as 1 g/(m²∙h), which is a practically significant result. The effect of the composition of 5 mM IFKhAN-92+0.5 mM DEDTC and its individual components on the electrode reactions of steel 20 in 4 M H3CCOOH at 100℃ was studied. It was shown that the efficient inhibition of steel corrosion by this mixture is due to the strong slowdown of both cathodic and anodic electrode reactions on the metal.

Keywords: low-carbon steels, acid corrosion, corrosion inhibitors, acetic acid, triazoles, sodium diethyldithiocarbamate

Int. J. Corros. Scale Inhib., 2026, 15, no. 3, 556-566
doi: 10.17675/2305-6894-2026-15-3-25

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