Corrosion Behavior of Cobalt Alloy Coating in NaCl Solution

Abstract:

Two kinds of Co-based coatings were obtained through the laser cladding (LC) and plasma transfer arc (PTA) process. The phase composition and microstructure of the coatings were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The corrosion behaviour of the different Co-based alloy coatings in 3.5wt% NaCl solution were compared by means of open-circuit potential (OCP), polarization curve and electrochemical impedance spectroscopy (EIS). XRD and SEM measurements demonstrated that the microstructures of the two different Co-based coatings were composed of primary solid solution γ-Co and eutectic structure Cr₂₃C₆, whereas, fish-bone typed (CoCrW)₆C was also detected in the coating produced by PTA. The polarization curves and EIS results showed that in 3.5wt% NaCl solution, the passivation zones of the two coatings occurred obviously, the self-corrosion potential of the two coatings shifted to the right, and the self-corrosion current density was much smaller than that of the substrate. In addition, the Co-based coating made by LC showed lower corrosion current density and larger diameter of a capacitive arc than that of Co-based coating produced by PTA, indicating the LC coating had the best corrosion resistance in the three samples.

• Periodical: Materials Science Forum (Volume 993)
• Pages: 1086-1094
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.993.1086
• Online since: May 2020
• Authors: Yue Hou, Hai Yan Chen*, Li Fan, Yu Rong Xu, Qian Cheng, Li Hua Dong
• Keywords: Cobalt Alloy, Corrosion Resistance, Laser Cladding (LC), Plasma Transfer Arc (PTA)

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