Electrochemical properties promotion of CrSiN coatings in seawater via Ni incorporation

Abstract

Nickel was incorporated into CrSiN coatings to improve their electrochemical properties. The incorporated Ni existed as elementary substance (zero valence) regardless of concentration (5.2–13.9 at %). Ni–CrSiN coatings with a thickness around 2.5 μm all presented the nano-composite structure composing of CrN crystal, amorphous nickel and amorphous SiNx. With increasing Ni content, the morphology of Ni–CrSiN coatings became compact. The electrochemical impedance spectrum results showed that the charge transfer resistance (Rct) of Ni–CrSiN coatings increased from 1.62 × 106 to 3.51 × 106 Ω cm2 as Ni concentration increased from 0 to 8.3 at %. Meantime, the corrosion current density (icorr) decreased to 18.54 nA/cm2 owing to the extra formation of nickel oxides. In contrast, icorr increased to 31.83 nA/cm2 at Ni concentration of 13.9 at % due to the premature pitting of passive layer.