The corrosive behavior of Cr/CrN multilayer coatings with different modulation periods

Cr/CrN multilayer coatings with varied individual layer thickness were synthesized by arc ion plating. The SEM results confirmed the clear periodicity of these coatings. They are known to contain bcc Cr, fcc CrN and hcp Cr2N phase by XRD patterns tested. The polarization curves show that the corrosion potential of the coatings with modulation periods of 603, 862, 1351 nm are more negative compared to that of the one with modulation period of 260 nm, which indicates that the lowest modulation period results in the highest corrosion resistance. The corrosion resistance of 1351 nm coating is higher than that of 603 nm and 802 nm coating. Nyquist diagrams show that these multilayer coatings are the corrosion of only coatings without the degradation of substrate. The 260 nm and 1351 nm multilayer coatings show higher charge transfer resistance but the 603 nm multilayer coatings present the lowest charge transfer resistance. These results can be attributed to the interface effect or nitride effect providing better resistance to diffusion of saline ion into the coatings, respectively. The corrosion resistance of coatings may mainly result from the interfaces and the nitride effect is secondary.