Effect of Surfactants on the Rate of Diffusion Controlled Anodic Dissolution of Copper in Orthophosphoric Acid

Abstract

The effect of Triton x-100 (non-ionic surfactant), sodium dodecyl sulphate (anionic) and cetyl pyridinium chloride (cationic) on the corrosion rate of copper in 8 M H3PO4 was investigated using potentiodynamic polarization and surface tension measurements. The inhibition behavior of these surfactants was investigated. The surface parameters of each studied surfactant were calculated from its surface tension. The parameters studied include the critical micelle concentration (CMC), maximum surface excess (Гmax), minimum surface area (Amin) and effectiveness (πCMC). The thermodynamic parameters of micellization (ΔGmic, ΔSmic) for the studied surfactants were also calculated. The greatest reduction of surface tension (effectiveness, πcmc) and higher minimum area (Amin) were achieved by Triton x-100 relative to the other two surfactants. This behavior agrees with the highest inhibition efficiency results achieved by Triton x- 100 obtained from potentiodynamic polarization method. The effect of temperature on the dissolution behavior of copper was studied at temperatures ranging from 25 to 40oC. A kinetic study of copper in uninhibited and inhibited acid was also discussed. The kinetic and activated parameters were calculated for the dissolution process.The adsorption of surfactants on copper surface in the acid solution was found to obey Kinetic-thermodynamic adsorption isotherm. The thermodynamic parameters were calculated.