Some ethoxylated fatty acids as corrosion inhibitors for low carbon steel in formation water

A series of ethoxylated fatty acids have been studied in order to evaluate their effect on the corrosion inhibition of low carbon steel. The behavior of these compounds is illustrated by the adsorption isotherms and weight loss measurements. The adsorption isotherms for saturated samples Pa(EO)(80) and St(EO)(80) exhibit an L-shaped isotherms while the unsaturated samples Ol(EO)(80), Li(EO)(80), and Soy(EO)(80) show an S-shaped isotherms. The inhibition efficiency of the first type increases with the decrease in the hydrophobic chain length; and also increases with increasing the number of the double bond present in the hydrophobic chain for the second type. Among all the tested inhibitors, the commercial inhibitor Soy(EO)(80) possesses the highest inhibition efficiency. The surface film is characterized by SEM and the morphologies promote the formation of inhibiting film on the steel surface. (C) 2002 Published by Elsevier Science B.V.