Study on the effect of alloying elements Ni, Al, and Si on salt spray corrosion resistance of gray cast iron

Abstract

In this paper, the effect of elements such as Ni, Al, and Si in gray cast iron on the atmospheric corrosion resistance of gray cast iron was studied by using corrosion weight gain, salt spray test, electrochemistry, and X‐ray diffraction. The results show that the corrosion behavior of gray cast iron can be divided into two stages. The later stage of corrosion resistance of gray cast iron with Ni element is better than the early stage of corrosion resistance, while the reverse is true for gray cast iron with Al element. There is no significant effect of increasing the Si content on the corrosion behavior of gray cast iron. The corrosion products of each specimen are all composed of Fe2O3, α‐FeOOH, γ‐FeOOH, and Fe3O4. After the comparison test, it can be concluded that the Ni element is seen to be conducive to the formation of protective rust layer with higher α‐FeOOH content. In addition, the rust layer of gray cast iron containing Al is loose and scaly, while the rust layer of gray cast iron containing Ni is dense and spongy. The addition of Ni element can make gray cast iron stable to improve the self‐corrosion potential and reduce the self‐corrosion current density, thus reducing the corrosion rate of gray cast iron.