Corrosivity of acidic sulphates in kraft recovery boilers

The corrosivity of molten and moist sodium bisulphate (NaHSO4) against carb on steel SA-178 was examined in the laboratory. The results suggest that th e carbon steel experiences severe pitting corrosion in contact with molten NaHSO4. The corrosion rate is much higher than that produced by moist NaHSO 4 in contact with tubes during a water wash, Corrosion by molten NaHSO4 pro duces a water-insoluble iron oxide/sulphide scale, whereas corrosion by moi st NaHSO4 results in water-soluble FeSO4. The difference in corrosion produ cts may be used as a fingerprint in identifying the type of corrosion.