DIYALA JOURNAL OF ENGINEERING SCIENCES

Abstract

ABSTRACT:- The inhibitive effect of magnesium oxide on the hot ash corrosion of steel structures of power generation station was studied using a kerosene fired furnace. Three alloys were selected including [SA 178A, 209 T1, 213 T11], prepared as rectangular pieces from water wall tubes and superheater tubes of a local power station. The heating chamber of the furnace had shelves on which specimens are placed. Mg(OH)2 was mixed with synthetic slag (67%wt V2O5 and 33% wt Na2SO4) at molar ratios of 1:1, 1:2 and 1:3, respectively and applied on the surface of the cleaned specimens. The tests were carried out at fixed (4 h) and various time intervals (2-10 h) to study the normal oxidation at various temperatures (550-950˚C). The rate of oxidation is accelerated in the presence of vanadic slag and resulted in increased corrosion rate with increasing temperature (550-950 oC ). X-ray diffraction indicated the formation of NaV3O8, Na2O.V2O4.5V2O5, Na4V2O7, VOSO4, Na2SO4 and iron oxide (Fe2O3) . The weight loss of the three alloys specimens indicated a Clear reduction in the degree of corrosion with increasing Mg(OH)2 content. The scale changed into a powder form which can be easily removed from the surface of the specimens. The best results were obtained with the mole ratio 3:1, which gave inhibition efficiency of 85% at 550°C. The inhibition efficiency increases with temperature decrease. With the introduction of Mg(OH)2 with the ash magnesium vanadate Mg3V2O8 was a major constituent together with some MgO.
Keywords:- Magnesium Hydroxide, Hot Ash corrosion, Inhibition.