SYNTHESIS OF BIO-BASED CORROSION INHIBITORS BASED ON ROSIN FOR LINE-PIPE STEEL

The synthesis and characterization of a series of bio-based surfactants based on gum rosin as natural products were investigated. Surface activities of these surfactants were investigated to correlate their structure and their performances. The new rosin adduct was prepared by reacting rosin with linoleic acid by Diels Alder mechanism. The adduct was esterified with poly(ethylene glycol) to produce nonionic surfactants. The chemical structure of the prepared surfactants was characterized by C-13 and H-1 NMR analyses. The surface activities of the surfactants were measured from the adsorption isotherm measurements which were determined from the relationship between the concentrations and surface tension of surfactants in aqueous medium at different temperatures. Critical micelle concentration (cmc) values were determined for water soluble surfactants. Surface-active parameters such as area per molecule at the interface (A(min)), surface excess concentration (Gamma(max)) and the effectiveness of surface tension reduction (Delta gamma) were measured from the adsorption isotherms of the modified surfactants. Corrosion inhibition behavior of RPEG600 and RLA-PEG600 compounds on steel surface were investigated by electrochemical impedance spectroscopy (EIS) and electrochemical polarization measurements. Electrochemical data show that both compounds suppressed the anodic and the cathodic reaction and act essentially as a mixed-type inhibitor. The results showed that corrosion inhibition of steel largely depends on the molecular structure and concentration of the inhibitors.