A new duplex PDMS/CrN coating was developed and the corrosion resistance of the system under seawater conditions was investigated. CrN coatings in four thicknesses were fabricated using a multi-arc ion plating system, and then the thin PDMS layers were covered on the coating surfaces by dip coating to fabricate the duplex PDMS/CrN coatings. Corrosion tests of the coatings were carried out using potentiodynamic polarization and electrochemical impedance spectroscopy in artificial seawater conditions. In a cross sectional image the PDMS layer was well adhered to the CrN layer. The corrosion current density for the duplex PDMS/CrN coating decreased by more than two orders of magnitude compared to the bare substrate, presenting the best corrosion protection efficiency. Furthermore, the impedance value was high to 10⁷ Ω cm², which improved by about three orders of magnitude compared to bare substrate. The excellent corrosion resistance of the duplex PDMS/CrN coating was attributed to the compact structure of the CrN coating combined with the good sealing barrier effect of the PDMS layer. Such duplex PDMS/CrN coating systems with superior corrosion resistance are considered as potential protective materials for mechanical assemblies for long-term service in marine applications.