Zinc Corrosion in Acidic Solutions Containing Single and Mixed Surfactants

AbstractThe influence of surfactant synergism on Zn corrosion inhibition in 0.1‐M HCl aqueous solutions has been determined at room temperature. Solutions of single and mixed surfactants consisting of sodium dodecylsulfate (SDS) and N,N‐dimethyldodecan‐1‐amine oxide (DDAO) in water and in 0.1‐M HCl were also prepared at room temperature. Critical micelle concentration (CMC) data were obtained through surface tension measurements as a function of mixing composition. A regular solution model was considered to analyze CMC values. The interaction parameter (β), the composition of mixed micelles (x) and the activity coefficients (f) were estimated by a regular solution model for all amphoteric–anionic mixed systems. β Vvalues showed synergism for the binary mixtures of these solutions in the absence and presence of 0.1‐M HCl at all investigated compositions. Zinc corrosion in single and binary SDS/DDAO mixed solutions at 5‐mM total surfactant concentrations in the presence of 0.1‐M HCl was also investigated at static and dynamic conditions. The weight loss data revealed corrosion inhibition activity obeyed the following order: binary (0.75 DDAO + 0.25 SDS) > binary (0.50 DDAO + 0.50 SDS) > single DDAO > single SDS, suggesting an enhancement in the corrosion inhibition activity of DDAO in the presence of a proper amount of SDS. Conductivity time measurements show a similar trend as that obtained by a weight loss method at (0.50 DDAO + 0.50 SDS). The results were illustrated on the basis of synergistic interaction between the mixed surfactants.