Corrosion behaviour of plasma sprayed Fe based metallic glass (Fe73Cr2Si11B11C3 (at%) coatings in 3.5% NaCl solution

In this study, Fe based amorphous/nanocrystalline composite coatings with different coating thicknesses were deposited on a mild steel substrate by atmospheric plasma spraying (APS) using a low Cr-containing gas atomised amorphous Fe73Cr2Si11B11C3 (at%) powder. The corrosion behaviour of the amorphous/nanocrystalline coatings of different thickness was investigated using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) analysis in a freely aerated 3.5 wt% NaCl solution. The variation in microstructural characteristics of the coatings with various coating thicknesses and the effect of the surface morphology, porosity content, surface roughness and amorphous content in the coatings have been correlated with the corrosion behaviour of the coatings. The results demonstrate that the corrosion resistance of the plasma sprayed Fe based composite coatings is better than that of the steel substrate regardless of coating thickness. Moreover, the best corrosion resistance of the coating with a thickness level of 110 +/- 12 mu m is attributed to (i) its optimum presence of content of amorphous, porosity, and surface roughness, (ii) excellent film and charge transfer resistance, and (iii) higher protection ability of the rust as compared to the other coating thickness values.