Investigation of Some Nonionic Surfactants as Corrosion Inhibitors for Carbon Steel in Sulfuric Acid Medium

Abstract

Four nonionic surfactants have been investigated as corrosion inhibitors for carbon steel type OL37 in sulfuric acid solution by electrochemical methods, FT-IR spectroscopy and metallurgical microscopy techniques. The influence of inhibitor concentration on the corrosion rate, inhibition effectiveness and surface coverage was analyzed. Results indicate that these surfactants accomplish a great inhibiting action on carbon steel corrosion and acts that a mixed-type inhibitor. The inhibition effect of noionic surfactants may be due to either the adsorption of inhibitor molecules building a protective layer or the constitution of an insoluble complex of the inhibitor adsorption obeys the Langmuir model. The negative value of thermodynamic parameter like Gibbs free energy of adsorptionΔGads∘indicates the spontaneity of adsorption process. Moreover, characterization utilizing FT-IR confirms the adsorption of inhibitors and the constitution of corrosion products on the carbon steel surface. EIS and potentiodynamic polarization results demonstrate its corrosion protection capacity.