SODIUM OLEATE AS AN EFFECTIVE CORROSION INHIBITOR FOR COPPER IN AERATED SULPHURIC ACID SOLUTIONS

The inhibitive effect of sodium oleate (SO), as an anionic surfactant, on copper corrosion in aerated 1.0 M H2SO4 solutions was investigated in the range of temperatures (20-70°C) by means of potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques at the open circuit potential (OCP). The results showed that the addition of the surfactant inhibits the sulphuric acid corrosion of copper. The inhibition process was attributed to the electrostatic adsorption of the surfactant and formation of an adsorbed film on the metal surface that protects the metal against corrosive agents. Energy dispersion X-ray (EDX) observations of the electrode surface confirmed the existence of such an adsorbed film. Polarization measurements showed that the surfactant acts as a mixed-type inhibitor. The inhibition efficiency increases with increasing surfactant concentration, while it decreases with solution temperature. Maximium inhibition efficiency of the surfactant is observed around its critical micelle concentration (CMC). Temkin adsorption isotherm fits well the experimental data. Thermodynamic functions for both dissolution and adsorption processes were determined.