Aqueous polymer colloidal nanoparticles, composed by poly(methyl metacrylate), butyl acrylate, and acrylic acid, as “core” (P(MMA/BA/AA)); and polyaniline (PAni) doped with dodecylbenzenesulfonic acid (DBSA), as “shell”, were prepared. The complete synthesis consisted of two-steps. In the first step P(MMA/BA/AA) particles were obtained in a semi-continuous process by free radical emulsion polymerization, followed by a second step where the chemical oxidative polymerization of aniline monomers upper the “core” surfaces occurred. Transmission electron microscopy images (TEM) and dinamic light scattering (DLS) confirmed the obtaining of spherical nanoparticles, which are stable for further free solid film preparation and coatings for metal protection. The free films were characterized by FTIR, Raman, UV–vis, X-Ray photoelectron spectroscopy (XPS), differential scanning calorimetry (DSC), thermogravimetry (TGA), optical and scanning electron microscopy (SEM), static contact angle, mechanical properties and water absorption. The metal protection was evaluated after check the adhesion properties and the impedance parameters. The presence of a low concentration of PAni-DBSA (3¿wt. %) on the acrylic polymer altered the hydrophilicity and the water uptake properties of the coatings without affecting the capability of obtaining passive layers for the protection of phosphatized carbon steel surface against corrosion, even after almost 20 days of immersion in NaCl aggressive solutions.

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