High temperature corrosion behaviour of stainless steels and Inconel 625 in hydroxide salt

Abstract

Biomass gasification had proven to be an alternative source of energy to coal gasification. However, it requires high temperatures of about 1000°C for biomass drying and reduction. On the other hand, to reduce the oxidation and corrosion of gasifier structural materials it is important to keep the gasifier working temperature as low as possible. One effective way of keeping the reduction temperature low is to use molten salts as catalyst during biomass gasification. However, by virtue, molten salts cause several corrosion issues in ferrous alloys. In this context, the present study investigates the effect of hydroxide molten salt on the corrosion behaviour of stainless steels such as 316 and 310 and Inconel 625. The samples exposed to the salt at 700°C for about 48 h was analysed for corrosion using weight loss method. A scanning electron microscopy analysis of the exposed samples revealed the depth of corrosion and change in microstructure due to molten salt attack. Although all the selected materials suffered severe corrosion, among all, Inconel 625 show higher corrosion resistance.