Sulphur and vanadium-induced high-temperature corrosion behaviour of different regions of SMAW weldment in ASTM SA 210 GrA1 boiler tube steel

Abstract

<jats:title>Abstract</jats:title><jats:p>Corrosion at elevated temperature is a serious problem in running thermal power plants because of the use of low-grade fuels that contain substantial amounts of sulphur, vanadium, sodium etc. This article reports the high-temperature corrosion of weld metal and heat-affected zone (HAZ) of shielded metal arc-welding (SMAW) weldment in GrA1 steel in a molten salt (Na<jats:sub>2</jats:sub>SO<jats:sub>4</jats:sub>–60% V<jats:sub>2</jats:sub>O<jats:sub>5</jats:sub>) environment at 900°C under cyclic conditions. The thermogravimetric technique was used to observe the kinetics of corrosion. The corrosion products formed on weld metal and HAZ of SMAW welded steel were characterized by scanning electron microscopy with energy dispersive X-ray analysis (EDX) and X-ray diffraction pattern. Weld metal was found to oxidize at a higher rate than those of HAZ due to the presence of sodium and sulphur in the inner oxide scale as confirmed by EDX, and this leads to high corrosion rate (in terms of weight gain).</jats:p>

Effect of burnishing on HVOF coated boiler steel against hot corrosion in actual boiler environment

“…Furthermore, the experimental results confirmed the function of ashes as alluded to in the literature, which is to contribute to the corrosion process through the alkali sulfate contents and SO 2 gas combination (dissolution of the scale) [34][35][36]. Scale spallation in the real boiler environment and the fluxing combat of molten salt may cause the lesser weight growth of uncoated specimens [37]. Plotting (weight-change/area) 2 reveals significant departures from the parabolic rate law, as shown by the scale spallation on the uncoated specimen's surface [38].…”