High Temperature Corrosion Behavior of Superheater Transition Joint (Stainless Steel-STBA 24) in Oil Fired Boilers

Abstract

High temperature corrosion of SUS 316, similar in morphology to that occurred at the actual transition joint in boilers, was albe to be reproduced with 80%Na₂SO₄-20%V₂O₅ synthetic ash coating and simulated combustion gas at 600°C. SUS 316 showed the poorest corrosion resistance among the tested 3 types of stainless steels (SUS 316, 321 and 347).
The poor resistance of SUS 316 is likely to be due to the effect of Mo in the steel, the formation of oxide scale with many defects on the surface of carburized base metal, and its cracking and flaking off by the thermal stress induced by the change of boiler load.
STBA 24 was corroded rapidly at the first stage but the oxide scale formed on this steel at 600°C was thick and compact, and thus showed good corrosion protective ability in the long run.