Microstructure and Pitting Corrosion Behavior of Plasma-Sprayed Fe-Si Nanocomposite Coating

In this study, Fe-Si nanoparticle composite coating (FSN) and Fe-Si microparticle composite coating (FSM) were prepared via atmospheric plasma spraying, and FSN was thermally treated under hydrogen atmosphere at 1120 °C for holding time of 2.5 h (TFSN). Under transmission electron microscopy, many unmelted nanoscale particles were observed in FSN, while no substantial particles were found in TFSN. On scanning electron microscopy analysis, pores and cracks were observed in FSM and FSN, while no defects were found in TFSN. Scanning electrochemical microscopy testing in 3.5 wt.% NaCl for 5 h revealed that FSM underwent severe pitting corrosion, FSN showed relatively minor pitting corrosion, and TFSN had no pitting corrosion.