Resistance Of Rare Earth Low-nickel-copper Alloy Cast Iron, Caustic Soda Corrosion

The alkali industry equipments which based on Inner Mongolian nature lye corroded seriously, and its service life was short. Developing low cast and high erosion resistance low alloy cast iron which can make basic industry developing prosperously and have profound significance on progressing economy of Inner Mongolia.In this paper, the corrosion behavior of RE-Ni-Cu and Cu-Ni alloy cast iron in the caustic lye of soda was researched. According to the requirement of caustic corrosion resistance, two kinds of alloy compositions of cast iron were designed, The corrosion rate and caustic corrosion resistance in the hot caustic lye of soda were measured by the dynamic condition hydrometer method and the static hydrometer method, the microscopic structure and phase were analyzed by the optical microscope and XRD, the corrosion features and components were analyzed by the SEM and XES.The results show that with rare earth increasing, the pearlitic structures of RE-Ni-Cu alloy cast iron are refined, meantime C model flake graphites are changed into quasiflake graphites and globular graphites, but when it is forereached, the chilling tendency is increased considerably, and the caustic corrosion resistance of alloy cast iron with 0.05%RE is better, the dynamic and the static condition corrosion rate are 0.30mm/a and 0.001mm/a. The structures of Cu -Ni alloy cast iron are refined by Cu, the caustic corrosion resistance is advanced. But when it is forereached, the copper compounds or Cu are precipitated. the caustic corrosion resistance of alloy cast iron with 4.5%Cu is better, the dynamic condition corrosion rate and static corrosion rate are 0.696mm/a and 0.0065mm/a. The caustic corrosion resistance of two kinds of cast iron is advanced by Cu-Ni enrichment on microscopic matrices. With temperature, concentration and current rate of caustic lye of soda, caustic corrosion resistance of cast iron is advanced.After dynamic erosion, the surface of alloy cast iron was made of cupped graphite pit and bellied carbide and matrices. The better of erosion resistance, the flatter of microscopic surface and the bigger of matrices area and the less of bellied carbide. With increasing of the erosive time, the corrosion rates of two mode alloy cast irons from high to low, at the same time, passivating happened. In the two models of alloy cast irons, the better synthetically mechanical property and more perfect ional corrosion resistance are provided by R2 rare earth alloy cast iron, and it is an ideal erosion resistance alloy cast iron.