Hot corrosion Evaluation of Carbon Steel caused by Mixtures of Vanadium Oxide and Sodium Sulfate Simulating Ashes of Fuel Oils

Abstract

Ashes from the burning of fuel oils containing mixtures of vanadium, sodium, sulfur and chloride compounds in the form of molten salts or oxides can cause hot corrosion of the carbon steel tubes located in the furnace at high temperatures with extremely disastrous effects. In order to simulate the melting ash in the laboratory, mixtures of sodium sulfate and vanadium pentoxide were used in different proportions of Na2O and V2O5 at temperatures of 500°C, 700°C and 800°C and in the exposure time of 12h, 24h and 36h using carbon steel coupons in the form of half-cane. The results were evaluated morphologically for the depth of the corrosive attack and the loss of mass using a confocal microscope where it was possible to evaluate the degree of corrosion caused by the action of the vanadate fluxes (Na2O.V2O5).The deepest pitting occurred in the ratio 2Na2O.V2O5 at the three test temperatures. At the temperature of 800°C and in the time of 36 hours, the average thickness loss in the coupons was 11%.