Preparation and application of self-assembled systems containing dodecylammonium bromide and chloride as corrosion inhibitors of carbon-steel

The application of surfactant systems as inhibitors of corrosion on metallic surfaces is discussed in this work. The focus is now driven to the influence of cationic surfactants’ counterions on the adsorption mechanism at carbon-steel surfaces. The surfactants dodecylammonium bromide (DDAB) and dodecylammonium chloride (DDAC) have been synthesized and used to prepare micellar and microemulsion formulations. The surfactants were dissolved in aqueous hydrochloric acid as micellar solutions, and in microemulsions containing n-hexane as oil phase and butan-1-ol as cosurfactant. After characterization by phase behavior studies, a number of these formulations with varying surfactant concentration have been tested against acidic corrosion on carbon-steel surfaces. Potentiometry assays were carried out to determine the extent of coverage on the metallic surface, and the adsorption mechanism was modeled with the Frumkin isotherm. Efficiencies of corrosion inhibition as high as 98% were obtained for the DDAC systems, and 96% for the DDAB systems. The results suggest that the protective surfactant film could resist changes in pH, salinity and temperature that might occur during typical applications involving metallic equipment or ducts under a broad range of experimental conditions. This is particularly interesting for industrial applications of microemulsions and other self-assembled systems, which could be used as templates for novel formulations of corrosion inhibitors.