Literature review Magnesiumoxide as inhibitor of hot oil ash corrosion

The accumulation of mineral ashes from residual fuel oil combustion on surfaces of various metals and alloys causes fouling and corrosion which results from the formation of low melting point aggressive compounds by the reaction between vanadium pentoxides and sodium sulphates in steam boilers and gas turbines. This paper reviews investigations into the effects of adding magnesium oxide to inhibit this form of corrosion. It has been found that by adding magnesium oxide to fuel oil the melting point of deposits is considerably increased and the formation of sodium vanadate is inhibited by formation of the more stable magnesium vanadates. This effect has been studied in actual plant conditions as well as in laboratory tests using melts of different compositions. Determination of the optimum amount of chemical inhibitor to be added has also been studied using various techniques. Magnesium oxide is found to be a very effective additive in combating hot ash corrosion by counteracting the effects of SO₃ in combustion gases and by increasing the melting points offuel ash constituents so as to increase their viscosity and thus reduce the diffusion of oxygen by up to an order of magnitude and thereby preventing the destruction of the protective oxide barrier film.