The adsorption and corrosion inhibition of some nonionic surfactants on API X65 steel surface in hydrochloric acid

Inhibition effect of three novel nonionic surfactants based on oleic acid monoamide namely ET-5, ET-20 and ET-40 against corrosion of steel in 1 M HCl was investigated by weight loss and electrochemical measurements. Scanning electron microscopy (SEM) and energy dispersion X-ray (EDX) were used to characterize the steel surface. The results showed that these surfactants act as a corrosion inhibitor in acidic medium and their inhibition efficiencies depend to the ethylene oxide content in the system. Adsorption of these surfactants on steel surface was found to obey Langmuir’s adsorption isotherm. The thermodynamic parameters Kads and ΔG°ads are calculated and discussed.

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► Corrosion of API 5L X65 is effectively reduced by the addition of the surfactants.
► The techniques include weight loss, potentiodynamic polarization, EIS and EDX.
► The surfactants act as a mixed-type inhibitor.
► The adsorption of surfactants obeys Langmuir adsorption isotherm.