Decay resistance ofdepends on its chemical composition and organization，this series of alloy foundry iron joins the nickel， chromium，copper and rare earth，electrode potential of nickel is higher，has very good performance of alkali resistance corrosion，the copper electrode potential is higher than the iron electrode potential，so foundry iron joins copper elements to improve its trona causticizing caustic corrosion ability. Range of passivation zoneis wide，rare earth has the deoxidation, desulphurization，effect of controllingthe inclusion，and can improve the density of alloy.
In this series of alloy foundry iron ，decay resistance of R2 is better than R1，after joining rare earth，reduce the number of the inclusion，reduce the speed of corrosion ，improve the corrosion resistance.
Corrosive substance of R4 is poorer than R1 and R2，because the graphite as the cathode，make the matrix around the metal is dissolved，graphite loses relying，strength is lower，under the washing of flow media，it is easy to fall off from the corrosion surface ，forms scallops.
The passage above talks about decay resistance analysis of alloy foundry iron.