Synthesis of nonionic surfactants and their inhibitive action on carbon steel in hydrochloric acid

A series of nonionic surfactants, namely: dodecyl 14-hydroxy-3,6,9,12-tetraoxatetradecyl phthalate (I), dodecyl 26-hydroxy-3,6,9,12,15,18,21,24-octaoxahexacosyl phthalate (II) and dodecyl 41-hydroxy-3,6,9,12,15,18,21,24,27,30,33,36,39-tridecaoxahentetracontyl phthalate (III) were synthesized to study their inhibition effect on carbon steel in 1.0 M HCl. Surface properties of these surfactants were determined by surface tension measurements. Potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and weight loss methods were also used to study the characteristics of these surfactants. The obtained results indicated that the studied inhibitors were good inhibitors. The inhibition efficiency was up to 94.9% at 1.0 × 10−2 M. A synergistic effect was also observed for the studied inhibitors with KI in 1.0 M HCl.

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► Nonionic surfactants as corrosion inhibitor for carbon steel in 1.0 M HCl.
► Nonionic surfactants exhibited good surface properties.
► The polarization studied indicated that the inhibitors act as a mixed type inhibitor.
► A equivalent circuit is suggested based on analysis of EIS data.
► The synergistic effect between KI and synthesized inhibitors 1.0 M HCl was studied.