[en] Decrease of corrosion resistance in nickel-copper-doped steel-titanium-St45 steel series in molten sodium phosphate is found by gravimetric method at 1073 K in the presence of manganese (2) and magnesium (2) salts. A shift of corrosion potentials to the region of electronegative values is experimentally confirmed in the given series of metals and steels. Titanium and nickel tendency to passivate in molten sodium phosphate is ascertained by taking the anode polarised curves. Such a property is not typical of cooper and St45