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The adsorption process of two polycations (pDADMAC and C-PAM) with different charge densities has been investigated using the quartz crystal microbalance technique with dissipation monitoring (QCM-D). The effect of the charge density of the polycation, the NaCl concentration, and the complexation with an anionic surfactant are addressed in this work. X-ray photoelectron spectroscopy and atomic force microscopy were utilized to analyze the adsorbate with respect to the film coverage and film structure. The corrosioninhibiting performance of the films on high-purity iron in a CO 2 saturated brine, at 258 8 8 8 8C, 1 bar CO 2 , and pH 4, was investigated by the linear polarization resistance technique. It was found that the polycations adsorbed onto the iron surface, but the corrosion rate of 1 mm yr 21 was not lowered. However, the polycations formed a complex with an anionic surfactant, and such films showed excellent inhibition performance. Both films, of pDADMAC/ SDS and of C-PAM/SDS, lowered the corrosion rate of iron below 0.01 mm yr 21 . The SDS concentration was below the cmc. It is believed that the SDS adsorbed into the preadsorbed polycation film, forming a complex structure resulting in a hydrophobic and dense film.