Long-term corrosion behavior of HVOF sprayed FeCrSiBMn amorphous/nanocrystalline coating

A FeCrSiBMn amorphous/nanocrystalline coating with 700 mu m in thickness and 0.65% in porosity, was prepared by high velocity oxygen fuel (HVOF) spraying process. The long-term corrosion behavior of the FeCrSiBMn coating was evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests in a 3.5% NaCl solution with a hard chromium coating as a reference. The FeCrSiBMn coating exhibited higher corrosion potential and lower corrosion current density than the hard chromium coating. The pore resistance (R-p) and charge transfer resistance (R-ct) of FeCrSiBMn coating were higher than those of the hard chromium coating. In addition, after immersion in the NaCl solution for 28 d, only small pores in the FeCrSiBMn coating were observed. All the results indicated that the FeCrSiBMn coating held superior corrosion resistance to the hard chromium coating. This could be attributed to the dense structure, low porosity and amorphous/nanocrystalline phases of the FeCrSiBMn coating.