Protection of low carbon steel in mineral acid solutions by alkylphenyl-substituted imidazolines

• D.R. Bazanov^1,2, Ya.G. Avdeev³, T.E. Andreeva³, N.A. Lozinskaya¹ and Yu.I. Kuznetsov³

¹ Department of Chemistry, M. V. Lomonosov Moscow State University, 119991, Moscow, Russian Federation
² Department of Chemistry, Shenzhen MSU-BIT University, 518172, Shenzhen, People’s Republic of China
³ A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Leninsky pr. 31, 119071 Moscow, Russian Federation

Abstract: Alkylphenyl imidazolines with phenyl (PHI), 4-methylphenyl (TI) and 4-isopropoxyphenyl (IPRI) substituents were synthesized and their properties in slowing down the corrosion of 08PS low-carbon steel have been studied in 2 M HCl, 2 M H₂SO₄ and 2 M H₃PO₄ (t=25–95°C). It has been demonstrated that for the protection of steel in mineral acid solutions, it is promising to employ not individual alkylphenyl-substituted imidazolines, but rather a combination of corrosion inhibitors containing them. Additives of 5 mM alkylphenyl-substituted imidazolines slow down the corrosion of steel in 2 M HCl (t=25–60°C). At higher temperatures, it is recommended to use a mixture of alkylphenyl-substituted imidazoline (5 mM)+ hexamethylenetetramine (HMT, 25 mM). The addition of TI (5 mM)+HMT (25 mM) in 2 M HCl (t≤95°C) ensures a corrosion rate of steel (k) no higher than 8.7 g/(m²·h). In 2 M H₂SO₄ (t=25–80°C) and 2 M H₃PO₄ (t=25–95°C), a significant reduction in the corrosion rate of 08PS steel is achieved by adding 5 mM of alkylphenyl-substituted imidazoline and 0.5 mM of KNCS. The maximum values of k are observed in the presence of these compositions based on PHI, TI and IPRI in 2 M H₂SO₄ (t≤80°C) are 2.4, 1.5 and 1.8 g/(m²·h), and in 2 M H₃PO₄ (t≤95°C) – 2.3, 1.3 and 0.99 g/(m²·h), respectively.

Keywords: low carbon steel, acid corrosion, corrosion inhibitors, hydrochloric acid, sulfuric acid, phosphoric acid, imidazoline

Int. J. Corros. Scale Inhib., 2024, 13, no. 4, 2313-2326
doi: 10.17675/2305-6894-2024-13-4-22

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