# Corrosion inhibition performance of some Schiff base anionic surfactant complexes of cobalt(II), copper(II), and zinc(II) on carbon steel in 1.0 M HCl

Research paper by Salah M. Tawfik, Mohamed F. Zaky

Indexed on: 11 Feb '15Published on: 11 Feb '15Published in: Research on Chemical Intermediates

#### Abstract

Four metallo-anionic Schiff base surfactants were synthesized and characterized by elemental analysis, FTIR, 1HNMR, UV–Vis spectroscopy, and atomic adsorption. The corrosion inhibition performance of Schiff base anionic surfactant complexes of cobalt(II), copper(II), and zinc(II) on carbon steel substrate in 1 M HCl was studied using weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy methods. It was seen that the synthesized anionic surfactant and their metal complexes decreased the corrosion rate of mild steel in acidic medium due to the adsorption on the metal surface, and it was found that the inhibition efficiency increased with increasing the inhibitor concentration and increasing the electronegativity of the transition metal. The adsorption of inhibitors on the carbon steel surface obeys the Villamil isotherm equation. Polarization curves show that the synthesized inhibitors are mixed-type inhibitors in 1 M HCl. $$\Delta G_{\text{ads}}^{0}$$ ranged from −32.77 to −39.74 kJ mol−1, which indicates that the adsorption process is a mixture of physical and chemical adsorption. Surface tension as a function of concentration of the surfactant in aqueous solution was measured at 25 °C. From these measurements, critical micelle concentration (CMC), effectiveness (πcmc), efficiency (pC20), maximum surface (Γmax) excess, and minimum surface area (Amin), were calculated. The synthesized metallo anionic surfactant showed high surface activity. Increasing the surface activity of the inhibitor solutions is accompanied by an increase in corrosion inhibition efficiency.