The influence of SO2 on high temperature oxidation of valve steels

The influence of 100 and 500 ppm of SO2 in air atmosphere on high temperature corrosion of steels (X33CrNiMn23-8, X50CrMnNiNbN21-9 and X53CrMnNiN20-8), utilized for the production of valves in diesel engines, has been investigated. These experiments have been carried out at 1173 K, i.e. at maximum temperature of valves, operating in diesel engines. It has been found that under these conditions the corrosion process did not follow exactly parabolic rate law with the exception of X33CrNiMn23-8 steel, containing maximum chromium concentration. In addition, it has been found that the presence of SO2 in oxidizing atmosphere increases the corrosion rate. The most important influence has been observed in the case of X50CrMnNiNbN21-9 steel, containing the lowest concentration of chromium.