Three gemini surfactants were synthesized having the same length of terminal chain but differing in the spacer chain length and they were evaluated as corrosion inhibitors for carbon steel in oilfield water using weight loss, EIS, potentiodynamic polarization and open-circuit potential measurements. These measurements revealed that the synthesized materials have served as effective mixed-type corrosion inhibitors. Their adsorption on a carbon steel surface was well described by means of the Langmuir adsorption isotherm. The activation parameters for the dissolution of carbon steel in solutions of oilfield water in the absence and presence of these inhibitors were calculated. The effect of immersion time on the stability and durability of protective films adsorbed on a carbon steel surface was studied using weight loss method. Ex situ inspection, i.e. post-exposure analysis, for the treated carbon steel surface has been performed using SEM, EDX and FT-IR tools.

Five homologous series of 4-(4-substituted phenylazo)phenyl 4-alkoxybenzoates (Ia–e) were prepared in which the substituent (X) was taken from CH₃O, CH₃, Cl, NO₂, and CN, while, within each homologous series, the length of the terminal alkoxy group varied between 6 and 16 carbon atoms. Compounds prepared were characterized by infrared spectroscopy, and their mesophase behaviour investigated by differential scanning calorimetry and polarizing optical microscopy. The results are discussed in terms of mesomeric and polarizability effects. In each group of compounds bearing the same alkoxy group, the mesophase – isotropic transition temperatures (T _c) were successfully correlated with the polarizability anisotropy of bonds to the substituent X.