Electroless coating of Fe 3 Si on steel in the molten salt

The corrosion‐resistive intermetallic compound Fe 3 Si could non‐electrolytically coat pure iron and mild steel. The disproportional reaction between Si and Si 4+ ions deposited the homogeneous Fe 3 Si layer on the Fe substrates, by using solid silicon and the molten salt composed of NaCl‐KCl‐NaF‐Na 2 SiF6‐SiO 2 . SiF 4 gas evaporation prevented from continuous siliconization, when only Na 2 SiF 6 was used as Si 4+ ion source. By adding SiO 2 into the salt as another source, the molten salt became endurable for repeated usage in air. The layer of Fe 3 Si single phase with silicon mole fractions of 24 ± 1 % grew thicker than 200 μm by immersing for a few hours at 973 – 1173K.