EFFECT OF GAS TEMPERATURE AND ITS FLUCTUATION ON THE HIGH TEMPERATURE CORROSION OF WTE BOILER MATERIALS

摘要

A thermal gradient corrosion test method capable of reproducing actual in-the-field corrosion phenomena was developed by considering the effect of gas temperature and gas temperature fluctuation. By taking these factors into account, the effect of gas temperature and its fluctuation on the corrosion rate of various alloys was quantitatively revealed. Also, corrosion phenomena experienced in actual plants, e.g. increased corrosion attack with an increase in alloying content, localized corrosion in welded areas, and changes in corrosion kinetics, were accurately reproduced. Thus, an accurate corrosion life evaluation was possible using short time data from the thermal gradient test. In general, an increase in gas temperature with a constant metal temperature and gas temperature fluctuations were shown to accelerate the break down of a protective oxide scale, the deposition of volatile chlorides, and the onset of mixed corrosion attack. Also, a new model of the corrosion process that considers the effect of gas temperature and its fluctuation is suggested.