Cast Iron (normally close grained SG irons) are a popular choice for castings for general purpose pumps handling water, solvents and caustic solutions at low temperature. Impellers can be in cast iron or bronze. Cast grey iron is an alloy of iron, carbon and silicon; easily cast; good pressure tightness in the as-cast condition. Gray iron has excellent dampening properties and is easily machined. It is standard material for general purpose pumps. Gray iron has corrosion resistance that is better than steel in certain environments. Cast iron is inferior to bronze in corrosion, erosion and cavitation resistance, Low initial cost would be the justification for a cast iron impeller where a bronze impeller can be used. For most water and other non-corrosive applications bronze satisfies the criteria of corrosion resistance, abrasive-wear resistance, cavitation resistance, casting and machining properties and cost. For most pumping applications cast iron is the preferred material for pump casings when evaluated against initial cost.
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