Corrosion testing in black liquors from kraft pulp and paper mill evaporators has confirmed that carbon steel has stable passivity in weak liquors (15% solids content), unstable passivity in intermediate liquors (25% and 33% solids content), and corrodes actively in strong liquors (45% and 49% solids content). The occurrence of rapid corrosion of carbon steels in evaporators handling liquors of intermediate solids content is caused by an abrupt switch from unstable passivity to active corrosion. Sudden changes in the corrosion state may be brought about by relatively small increases in the sulfidity and temperature of the liquor or by the use of modern carbon steels having higher silicon contents than those used in the past. Galvanic coupling of active carbon steel with stainless steel increases the active corrosion rate of the carbon steel.

Subject
Materials, Hydroxides, Active corrosion, Corrosion rate, Liquor, Solids, Black liquors, Steel, Passivation, Carbon steel, Duplex stainless steel, Stainless steel, Corrosion potential
Keywords:
Austenitic stainless steels, Carbon steel, Corrosion Testing, Duplex Stainless Steel, Pulp and Paper
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2006
Association for Materials Protection and Performance (AMPP)
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