Electrochemical Studies of Structural Materials in Acidic Peroxide Media

Corrosion in paper industries is responsible not only for weakening of metal structures but also for pollution of process liquors and contamination of products. The bleaching sections in pulp and paper industry are among the worst affected by the ravages of corrosion. In bleach plants the materials are exposed to highly corrosive bleaching liquors. Now day's new norms of safety of environment are forcing paper industries to use peroxide as a bleaching agent instead of chlorine. So in the present study an effort has been done to propose an appropriate material for the construction of future bleach plants keeping in mind their mechanical factors and cost of the material. Accordingly electrochemical polarization tests, E vs. time curve, potentiodynamic polarization curve and cyclic polarization curve were performed on stainless steels samples of 316L, 317L, 2205 and 254SMO in peroxide containing solutions having H₂O₂, 500 and 1000 parts per million (ppm). The pH of these solutions was kept 4. The Chloride content varied from 0 to 1000 ppm. These tests was performed at room temperature. These tests showed increased resistance against corrosion in order of: 316L<317L<2205<254SMO. Thus 254SMO shows highest resistance for attack of corrosion but keeping in mind fabrication and cost aspects optimal material for treating these peroxide media is recommended to be SS 2205.