In this contribution it will be shown that plasma enhanced chemical vapor deposition (PECVD) of silicon containing organic compounds is a promising approach for the corrosion protection of metals (steel and magnesium alloys). When the deposition process is preceded by a suitable plasma treatment, which depends on the particular metal under study, a marked increase of the protective properties measured with electrochemical impedance spectroscopy (EIS) is detected. The highest impedance modulus obtained for Mg is 450 KΩ·cm2, 8000 times higher than for the bare metal. Highly protective coatings are obtained for inorganic films, free of sylanols. A marked decrease of the impedance modulus of coated substrates has been registered after immersion in electrolyte solution due to the presence of pinholes which represents defect points where localized corrosion starts.