ENVIRONMENTAL ATTACK OF 2.25CR - 1MO STEEL

2.25Cr - 1Mo steel is widely used in superheaters and reheaters in thermal power plants. These undergo severe corrosion due to the salt deposits formed on the surface exposed to flue gases. To evaluate the influence of corrosive constituents of the deposits on the life of the components, it was attemped to carry out hot corrosion tests on 2.25Cr-1Mo steels in salt mixture containing 40% K2SO4 and 60% NaCl (by weight). The salt coating resulted in enhanced corrosion with increase in depth of attack compared to the tests conducted in still air. X-ray diffraction (XRD) studies indicated that the surface of uncoated specimens showed only oxides whereas the salt coated specimens showed both oxides and sulphides. These sulphides were responsible for accelerated corrosion.