A study on corrosion resistance characteristics of PVD Cr-N coated steels by electrochemical method

• Published in: Surface & coatings technology 2002-02, Vol.150 (2), p.319-326
• Main Authors: Ahn, S.H, Choi, Y.S, Kim, J.G, Han, J.G
• Format: Article
• Language: English
• Subjects: Applied sciences; Bode plot; Cathodic arc deposition; Corrosion; Corrosion prevention; Electrochemical impedance spectroscopy; Exact sciences and technology; Metals. Metallurgy; Porosity; Potentiodynamic polarization test; Warburg behavior
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/S0257-8972(01)01529-8

The corrosion behavior of Cr-N coated steels with different phases (α-Cr, CrN and Cr 2N) deposited by cathodic arc deposition on AISI H13 steel was investigated in a 3.5% NaCl solution at ambient temperature. Potentiodynamic polarization tests, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) were the techniques applied to characterize the corrosion behavior. It was found that the CrN coating had a lower current density from potentiodynamic polarization tests than others. The porosity, corresponding to the ratio of the polarization resistance of the uncoated and the coated substrate, was higher in the Cr 2N coating than in the other Cr-N coated steels. EIS measurements showed, for most of the Cr-N coated steels, that the Bode plot presented two time constants. Also, the Cr 2N coating represented the characteristic of Warburg behavior after 72 h of immersion. The coating morphologies were examined in planar view and cross-section by SEM analysis and the results were compared with those of the electrochemical measurement. The CrN coating had a dense, columnar grain-sized microstructure with minor intergranular porosity. From the above results, it is concluded that the CrN coating provided a better corrosion protection than the other Cr-N coated steels.