Although the macroscopic changes of the ductile iron studied are not obvious, the corrosion surface is slightly uneven after enlarged as shown in the figure.
Control of diffusion rate on the corroded surface.Oxygen passes through the liquid medium through the graphitized corrosion residue layer on the surface of the cast iron to the metal base surface of the cast iron.The adhesion and compactness of the surface layer consisting of graphite network and corrosion products can improve the corrosion resistance to a certain extent.