Corrosion investigations on secondary treated paper mill effluents

– This paper aims to report on corrosivity of secondary-stage paper mill effluent and corrosion performance of stainless steels.

– For this purpose, immersion test and electrochemical polarization tests were conducted in mill and synthetic effluent to evaluate the uniform and localized corrosion.

– Corrosivity of mill effluent has been compared with synthetic and primary-stage effluent of the same mill. It is observed that anions present in them, viz. SO₄−, PO₃4−, NO₂− and NO₃−, impart inhibition, whereas Cl− and chlorophenols enhance the corrosivity of the effluent. The overall effect of various components was reduction in corrosivity of secondary mill effluent.

– These observations can be useful for material selection and helpful in corrosion mitigation in paper mill effluent treatment plants.