The rapid exploitation of marine resources in China has heightened the need for advanced marine engineering equipment and imposed more stringent requirements on the surface performance of its key components. CrN/NbN coatings, with their excellent corrosion and wear resistances, demonstrate potential for applications in marine service environments. In this study, CrN/NbN coatings were deposited on 45# steel substrates using arc ion plating technology. A multilayer/nanolayer design and ion etching process were implemented to reduce coating defect densities, thereby enhancing overall coating performance. Scanning electron microscopy analysis revealed that S2–S6 coatings exhibited fine columnar structures, with well-defined and cohesive sublayer interfaces in S2 and S3 multilayer coatings. XRD and TEM analyses confirmed that the primary phases of the coatings were CrN and NbN. HRTEM images of the S6 coating demonstrated a nanolayer structure with a modulation period of 8.9 nm, where CrN and NbN sublayer thicknesses were approximately 2.7 nm and 6.2 nm, respectively. A coherent interface was observed in the S6 coating, accompanied by the interdiffusion of Nb and Cr elements between the CrN and NbN sublayers. The fast Fourier transform image displayed streak-like features characteristic of stacking faults, as well as two sets of diffraction patterns indicative of coherent sublayer interfaces. Nanoindentation tests revealed that among the fabricated coatings, the S1 monolayer coating exhibited the lowest hardness of (21.8 ± 0.7) GPa, while the S4 coating demonstrated the highest hardness of (30.1 ± 1.4) GPa, attributed to its coherent interfaces and stacking faults. Ion etching had minimal impact on coating phases and mechanical properties. However, ion bombardment effectively interrupted the continuous growth of large particles, resulting in smoother surfaces and interfaces and thereby reducing surface defect proportions. The defect percentages for S3 and S5 coatings were (2.7 ± 0.19)% and (2.43 ± 0.49)%, respectively. These lower defect densities contributed to higher pore resistance (R_po) and charge transfer resistance (R_ct). As sublayer thickness decreased, the electrochemical and tribocorrosion performance of CrN/NbN coatings improved progressively, with the S6 sample achieving the lowest corrosive wear rate of 2.42 × 10^–6 mm³/(N·m). The tribocorrosion failure mechanism was preliminarily explored, identifying layer-by-layer peeling as the dominant failure mode. Compared to NbN monolayer coatings, CrN/NbN multilayer/nanolayer coatings exhibited superior mechanical properties and corrosion resistance due to interface blocking and reinforcing effects. Furthermore, the application of ion etching to CrN/NbN multilayer/nanolayer coatings enhanced their electrochemical corrosion and tribocorrosion properties by disrupting the growth of large defects.