Affordable electrolytic ferrotitanium alloys with marine engineering potentials

Fe2O3 and TiO2 powders were compounded in different proportions at elevated temperatures. Porous thin pellets were made from the compounded oxides and then electro-reduced to the respective ferrotitanium alloys and/or intermetallic compounds in solid state in molten CaCl2. Typical electrolysis conditions were 800-1000 °C, 2.8-3.2 V and 4-15 h. X-ray diffraction, scanning electron and optical microscopy, and potentiodynamic polarisation were used to characterise the oxide precursors and/or the products. The results showed that the obtained Fe-Ti alloys achieved the designated elemental compositions. When the Fe content in the oxide precursor was less than 50 wt.%, the products were mainly mixed Ti and Fe-Ti alloys. At higher Fe contents, the products changed to a mixture of Fe2Ti and Fe. Between 8 and 15 wt.% Fe, the products sintered most severely. The Fe-rich Fe-Ti alloys had better corrosion resistance than a common ship hull steel (E36) in simulated sea water, i.e. the aqueous solution of 3 wt.% NaCl. The Ti-rich Fe-Ti alloys (8 wt.% Fe) had good corrosion resistance to the 1.0 mol/L HCl solution. The addition of Nb in the alloys improved the corrosion resistance, but the addition of Al caused the opposite effect.