The corrosion-resistive intermetallic compound Fe3Si can non-electrolytically
coat the iron substrate at 973-1173K in the molten salt composed of
NaCl-KCl-NaF-Na2SiF6-SiO2. However, the adhesion of Fe3Si layer was
weak because of the crack formation in the Fe3Si layer. The mechanism of the
layer growth and defect formation was stud-ied experimentally. The marker
experiments showed that the salt was caught up on the initial surface and left
as the large voids in the layer. The fast deposition of silicon on pure iron
surface and the quick growth of Fe3Si wrapped the salt in the layer at the
first stage of deposition. The Si penetration from the Fe3Si layer into the
a-Fe sub-strate was small due to the slow diffusion of Si in a-Fe. The fast Fe
diffusion in the Fe3Si layer left the Kirkendall holes. The formation of
these defects could be sup-pressed in the high Si concentration-iron alloys.