Protection of low-carbon steel in phosphoric acid solutions by mixtures of Catamine AB 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: Composite inhibitors have been developed for the protection of low-carbon steel St3 in phosphoric acid solutions based on the commercially available product Catamine AB (an aqueous solution of a mixture of alkylbenzyldimethylammonium chlorides, [H₃C–(CH₂)_n–N⁺(CH₃)₂CH₂C₆H₅]Cl^–, where n=9–17). Catamine AB in individual form provides only weak protection of steel in phosphoric acid media. Mixtures of Catamine AB with various additives (potassium iodide, potassium thiocyanate, sodium diethyldithiocarbamate, Captax (2-mercaptobenzothiazole), 2,2′-dibenzothiazyl disulfide, thiourea, phenylthiourea, tolylthiourea, diphenylthiourea, and cysteine) were tested as steel corrosion inhibitors. It was found that the addition of 5.0 mM Catamine AB + 0.5 mM KCNS or 5.0 mM Catamine AB + 0.5 mM Captax to H₃PO₄ solutions results in efficient inhibition of low-carbon steel corrosion in this medium. These composite inhibitors protect St3 steel in H₃PO₄ solutions over wide ranges of temperature (0–95°C) and acid concentration (1–8 M). Based on the analysis of the temperature dependence of the protective effect of the proposed composite inhibitors, it was concluded that they can be classified as high-temperature corrosion inhibitors.

Keywords: acid corrosion, phosphoric acid, low-carbon steel, corrosion inhibitors, Catamine AB, potassium thiocyanate, Captax

Int. J. Corros. Scale Inhib., 2026, 15, no. 2, 573-583
doi: 10.17675/2305-6894-2026-15-2-30

Download PDF (Total downloads: 2)

Back to this issue content: 2026, Vol. 15, Issue 2 (pp. 1-583)