Abstract
Erosion-corrosion has been observed in evaporators, digesters, and other pulp mill equipment in the pulp and paper industry. Erosion-corrosion in these systems occurs due to a combination of caustic conditions and suspended solids. While not fully explored, studies suggest that it may interfere with passive film formation in caustic conditions. The resulting accelerated corrosion forces the shutdown of affected equipment, and thus the cost of erosion-corrosion can be great and possible preventive measures must be researched. In order to better understand the mechanism of this corrosion process, electrochemical tests were performed on typical materials used in the construction of evaporators. Linear polarization resistance (LPR) measurements were used to get instantaneous corrosion current under flow conditions with differing percentages of solid and flow velocity. Corrosion rate (in mils per year or mpy) was quantified using a rotating cylinder electrode (RCE) method in a white liquor solution with hard particles simulating field conditions for the digesters or evaporators. Corrosion products remaining on the specimen surface were examined using an optical microscope.
