Effect of W, Mo, and Ti on the Corrosion Behavior of Low-Alloy Steel in Sulfuric Acid

The effects of W (0.05 wt% W), Mo (0.05 wt% Mo), and Ti (0.05 wt% Ti) addition on the corrosion resistance of low-alloy steel used in flue gas desulfurization systems were examined using electrochemical measurements in a 10 wt% sulfuric acid (H2SO4) solution. The corrosion rate increased in the following order: W steel < Mo steel << Ti steel. The surface analysis indicated that the type and quantity of inclusions by steel are as follows: W steel (manganese sulfide [MnS]) < Mo steel (MnS, molybdenum disulfide [MoS2]) << Ti steel (MoS2, titanium sulfide [TiS]). The corrosion rate was influenced by sulfide inclusions in the steels. In particular, the corrosion rate of Ti-ontaining steel was the highest due to a large number of TiS inclusions formed during the steel manufacturing or corrosion processes.