The influence of small amounts of KCI(s) and ZnCI2(s) on the high temperature corrosion of a Fe-2.25Cr-1 Mo steel at 300 and 400°C

摘要

It is well known that alkali and heavy metal salts, especially lead and zinc chlorides increase the corrosivity of deposits even at relatively low material temperatures (about 250°-450°C).This causes large corrosion problems in e.g. boilers firing fuels containing these species. In order to limit fouling of these boiler and increasing fuel flexibility it is important to better understand the corrosion mechanism caused by these species. Recent studies have shown that KCI(s) is very corrosive towards the low-alloyed steel Fe-2.25Cr-1 Mo at 400 °C [1,2]. As the initial reaction is very fast it was studied by ESEM in-situ exposures and analysis. The initial stages of corrosion are considered too strongly influence the later corrosion behavior. It was shown that rapid corrosion is initialized well below 400 °C [2]. This can be seen in Figure 1 where the corrosion behavior of a KCI particle is monitored in the ESEM at 300-400 °C [2]. The aim with this work is to study the corrosion behavior of ZnCI2 and KCI at 300-400 °C on the low alloyed steel Fe-2.25Cr-1Mo.The initial stages may be studied with the ESEM in-situ exposure technique. Longer exposures times (up to 168h) will be studied using tube furnaces and in-situ TG with a Rubotherm system. The corrosion products will be investigated by FIB/SEM, SEM/EDX and XRD.