Effect of Fe(III) salts on the protection of low carbon steel in hydrochloric acid solutions by some corrosion inhibitors

• Ya.G. Avdeev, A.V. Panova and Yu.I. Kuznetsov

A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Leninsky pr. 31, 119071 Moscow, Russian Federation

Abstract: The effect of Fe(III) salts on the protection of 08PS low carbon steel in 2 M HCl and 2 M H₃PO₄ at 20 and 60°C by corrosion inhibitors (PKU-E, Catapin A, Catapin BPV, Soling m. Z, Soling m. L, VNPP-2, Invol-2 m. A and NORUST CM 150 C) and their mixtures with hexamethylene¬tetramine (HMT) has been studied. None of the individual and two-component corrosion inhibitors studied can provide efficient protection of steel in HCl and H₃PO₄ solutions if significant amounts of Fe(III) cations are accumulated in them. In H₃PO₄ solutions containing Fe(III) phosphate, efficient protection of steel can be obtained by the formulation comprising 2 g·L^–1 VNPP-2 + 0.5 mM KNCS + 200 mM HMT as the corrosion inhibitor. The same formulation protects steel in 1 M HCl + 1 M H₃PO₄ (20 and 60°C) with up to 0.10 M Fe(III) cations accumulated in it. Solutions of a HCl + H₃PO₄ mixture inhibited by the formulation of VNPP-2 + KNCS + HMT can be an alternative to inhibited solutions of individual HCl in case of potential accumulation of Fe(III) chloride in them.

Keywords: low carbon steel, acid corrosion, corrosion inhibitors, hydrochloric acid, phosphoric acid, iron(III) chloride, iron(III) phosphate

Int. J. Corros. Scale Inhib., 2024, 13, no. 4, 2300-2312
doi: 10.17675/2305-6894-2024-13-4-21

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