Chiang Mai Journal of Science

The corrosion mechanism and effect of Mo on microstructure of this alloy has been evaluated in this paper. When this alloy undergoes attack by dilute sulfuric acid (H2SO4 10%), the carbide/ matrix interface will be corroded first. The corrosion process is local and intergranular causing Fe and Cr depletion at the eutectic carbides/matrix interface. When the corrosion process spreads deeper, the surface of this material will be peeled off and destroyed. The effect of Mo on the corrosion resistance of this alloy has been demonstrated by the fact, that an increase in the content of Mo in the alloy is accompanied with the increase in chromium, molybdenum contents in the austenitic matrix; especially Mo concentrates most at the carbides/austenite matrix interface and with increasing of Mo the microhardness of matrix phase increase. In the zone of the eutectic carbides/matrix interface, where Mo element concentrates mainly, it can be seen a protective film which prevents alloy from the attack by acid and thus reduces the corrosion rate and increases the corrosion resistance of alloys.