Abstract: A method of operating a thermal installation other than a gas turbine and use of such a method for inhibiting vanadic corrosion is disclosed herein. Embodiments of the invention relate to a method of operating a thermal installation comprising a combustion chamber fed with a fuel contaminated with vanadium, with sulfur and possibly with sodium. The combustion chamber is also fed with boron and with magnesium, in quantities such that the magnesium molar ratio m=MgO/V2O5 and the boron molar ratio b=B2O3/V2O5 satisfy the conditions (i) m?2+b; (ii) m?3+2b; (iii) b?0.5 and (iv) b?2, so that the combustion products comprise magnesium vanadate, mixed magnesium boron oxide and possibly sodium borate.