Corrosion Behavior of Cast Iron in Engine Coolant

Electrochemical impedance spectroscopy, potentiodynamic polarization curves, and the Mott-Schottky method were used to study the corrosion behaviors of vermicular graphite cast iron and gray cast iron and the characteristics of the passive films on the surfaces of vermicular graphite cast iron and gray cast iron in engine coolant. The results showed that the passive film formed on the surface of vermicular graphite cast iron exhibited a low density of defects and had a higher protective property compared to that on gray cast iron under the same conditions. Flake graphite was conducive to the formation of the passive film on the surface of cast iron, but the dissolution rate of the passive film on the surface of gray cast iron was higher than that of vermicular graphite cast iron. Vermicular graphite cast iron showed better corrosion resistance than gray cast iron in engine coolant. The charge transfer resistance of the anodic reaction of vermicular graphite cast iron and gray cast iron in engine coolant was much greater than that of the cathodic reaction, and the control step of the corrosion process in the system was the anodic reaction process.