Phytic acid-doped pyridyl-diindolylmethane as green corrosion inhibitor for mild steel in acidic media

• G. Jiang^1,2, F. Yang² and H. Zhao¹

¹ State key Laboratory of Advanced Marine Materials, Ningbo Institute of Materials Technology and Engineering Chinese Academy of Sciences, Ningbo 315201, P. R. China
² School of Materials Science and Engineering, Shenyang University of Chemical Technology, Shenyang 110142, P. R. China

Abstract: Corrosion is a pervasive problem that affects the integrity, safety, and longevity of structures, equipment, and infrastructure in numerous industries. Conventional corrosion control measures often rely on the use of toxic and environmentally harmful inhibitors that pose a significant threat to human health and the environment. It is important to develop sustainable corrosion inhibitors that are both effective and environmentally responsible. 3,3′-Diindolylmethane (DIM), as a substance derived from natural products (e.g., cruciferous plants), is biodegradable and has low toxicity, but its study in metal corrosion inhibition has rarely been reported. This study employed phytic acid as both catalyst and chelating agent to introduce a pyridine group into diindolylmethane via a one-pot reaction, yielding a diindolylmethane derivative (PAP-DIM). Its corrosion inhibition effect on Q235 steel in 1 M HCl was investigated by polarization curves, electrochemical impedance spectroscopy and corrosion product analysis. PAP-DIM is a mixed-type inhibitor and achieves a corrosion inhibition efficiency of 98.58% at a concentration of 50 mg/L for Q235 steel in 1 M HCl. This high efficiency is attributed to the formation of a protective layer on the surface of the mild steel, which is corroborated by XPS analysis, which prevents the diffusion path of aggressive ions, thus reducing corrosion.

Keywords: diindolylmethane, organic corrosion inhibitor, green corrosion inhibitor

Int. J. Corros. Scale Inhib., 2025, 14, no. 4, 2184-2200
doi: 10.17675/2305-6894-2025-14-4-24

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