The corrosion-resistive intermetallic compound Fe3Si could
non-electrolytically coat pure iron and mild steel. The disproportional reaction
between Si and Si4+ ions deposited the homogenous Fe3Si layer on
the Fe
substrates, by using solid silicon and the molten salt composed of
NaCl-KCl-NaF-Na2SiF6-SiO2. SiF4 gas evaporation prevented from
continuous siliconization, when only Na2SiF6 was used as Si4+ ion source.
By adding SiO2 into the salt as another source, the molten salt became
endurable for repeated usage in air. The layer of Fe3Si single phase with 24 +-
1 mol pct Si grew thicker than 200 micro m by immersing for a few hours at
973-1173K.