Investigation of oxide growth mechanisms in developing protective oxide layer of superheater materials in alkali salt environment
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Date
2019-07
Authors
Farliana Azira Ahmad Tarmizi
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Abstract
High temperature corrosion is the major defect in biomass fired power generation due to chlorine-induced corrosion at high temperature. The oxidation behaviour of Stainless Steel 304 SS at four different temperature (800 °C, 900 °C, 1000 °C, and 1100 °C) was studied to form a protective oxide layer and protect the underneath steel. The oxidation products were investigate the surface morphology, elemental distribution and phase identification details by X-ray Diffraction (XRD), Field Emission Secondary Electron Microscope Equipped with Energy Dispersive X-ray Spectroscopy (FESEMEDX) and mass gain measurement. From the results, the protective oxide scales was successfully formed on the Stainless Steel 304 SS pre-oxidised sample at 800 °C. Next, the corrosion behaviour of Stainless Steel 304 pre-oxidised sample and Stainless Steel 304 SS raw in alkali salt environment that consists of 95.5 wt% KCl + 4.5 wt% NaCl were investigated and compared. The corrosion test was conducted at 700 °C for 24 hours. The corrosion products were inspected by the same characterization as oxidation products excepting the mass gain measurement was replaced with mass loss measurement due to the spallation of oxide scales. The pre-oxidised Stainless Steel 304 SS is better corrosion resistance compared to Stainless Steel 304 SS raw as the formed of oxide scales which is can prevent corrosion reagent from penetrate into the substrate.