Some Nonionic Surfactants as Inhibitors of the Corrosion of Iron in Acid Chloride Solutions

The inhibition effect of the surfactants 1,2-hexanediol (HD), 1,2,3-octanetriol (OT); 1,2,3-nonanetriol (NT); and 3,7-dimethyl-1,2,3,6,7-octanepentol (DOP) on the corrosion of iron in 1 M hydrochloric acid (HCl) was studied. Results obtained from gravimetric methods showed inhibition efficiencies increased with increasing surfactant concentrations and attained a maximum around their critical micellar concentration (cmc). A comparative study of corrosion inhibition of surfactants indicated DOP was the best inhibitor. Polarization measurements showed DOP was a cathodic type-inhibitor and acted on the cathodic reaction without modifying the mechanism of the hydrogen evolution reaction. DOP appeared to function through a general adsorption mode following the Langmuir adsorption isotherm. The effect of temperature on the corrosion behavior of iron in both 1 M HCl and 1 MHCl with addition of various concentrations of DOP was studied in the temperature range from 18°C to 48°C. The associated activation corrosion and free adsorption energies were determined.