Effect of wood species on corrosion behavior of carbon steel and stainless steels in black liquors

Black liquors produced by pulping different wood species can have different corrosivity towards carbon steel equipment in pulp mills. Inorganic constituents of black liquor alone do not correlate well with the corrosivity of different black liquors. Organic constituents of the black liquor have significant effect on determining its corrosivity. However, understanding of the role of individual organic constituents or group of constituents of black liquors in overall black liquor corrosivity is generally lacking. The objective of this study was to determine the effect selected wood species on the corrosivity of their black liquors which contained similar inorganic constituents. The role of black liquor constituent, pyrocatechols, whose presence in the black liquor has been associated with an increase in corrosion of carbon steel, was also studied. Results from electrochemical tests point to the mechanisms by which the catechols may participate in the accelerated corrosion of carbon steels. This study demonstrates the role of organic constituents of the black liquor in determining its corrosivity.